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Glossary of Terms2012-07-11 16:07:32 admin

The following is a list of glossary of terms & terminology used in the Plast icsIndust ry.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A-stageThis is a very early stage in the react ion of certain thermoset t ing resins wherethe molecular weight is low and the resin is st ill soluble in some liquids and st illf usible.

Abrasion ResistanceThe abilit y to withstand the ef fects of repeated wearing, rubbing, scraping,etc., that tend to remove material f rom it s surface.

Absolute ViscosityThe tangent ial force on unit area of either of two parallel planes at unitdistance apart when the space between the planes is f illed with the f luid inquest ion and one of the planes moves with unit dif ferent ial velocit y in it s ownplane. The C.G.S. unit for absolute (or dynamic) viscosit y is poise (dyne-sec./sq. cm.). Cent ipoise (0.01) is of ten used.

AcceleratorA substance that hastens a react ion, part icularly one which speeds up thevulcanizat ion of rubber. Also known as Promoter.

AccumulatorA term used mainly with reference to blow molding equipment whichdesignates an auxiliary ream ext ruder which is used to provide ext remely fastparison delivery. The accumulator cylinder is f illed with plast icated meltcoming f rom the ext ruder between parison deliveries or “shots” and is storedor “accumulated” unt il t he plunger is required to deliver the next parison.

Acrylic Resin .A synthet ic resin prepared f rom acrylic acid or f rom a derivat ive of acrylicacid,

AcrylonitrileA monomer with the st ructure (CH2:CHCN). It is most useful in copolymers. It scopolymer with butadiene is nit rile rubber, and several copolymers withstyrene exist that are tougher than polystyrene. It is also used as a synthet icf iber and as a chemical intermediate.

Acrylontrile Butadiene Styrene (ABS)Acrylonyt rile and styrene liquids and butadiene gas are polymerized togetherin a variety of rat ios to produce the family of ABS resins.

ActuationTo put into mechanical act ion or mot ion.

AdditiveA substance compounded into a resin to enhance or improve certaincharacterist ics.

Adhesion PromoterA coat ing which is applied to the subst rate before it is ext rusion coated withthe plast ic and which improves the adhesion of the plast ic to the subst rate.

AdhesiveA substance which applied as an intermediate is capable of holding materialstogether by surface at tachment .

Af f inityThe at t ract ion for another substance.

AgingThe change of a material with t ime under def ined environmental condit ions,leading to improvement or deteriorat ion of propert ies.

Air GapIn ext rusion coat ing, the distance f rom the die opening to the t ip formed bythe pressure roll and chill roll.

Air RingA circular manifold used to dist ribute an even f low of the cooling medium, air,onto a hollow tubular form passing through the center of the ring. In blowntubing, the air cools the tubing uniformly to provide uniform f ilm thickness.

Air-assist FormingA method of thermoforming in which a f low of air pressure is employed topart ially pre-form the sheet immediately prior to the f inal pull down onto themold using vacuum.

Alkyd ResinPolyester resins made with some fat t y acid as a modif ier.

AlkylA general term for monovalent aliphat ic hydrocarbon radicals.

AlloyComposite material made up by blending polymers or copolymers with otherpolymers or elastomers under selected condit ions, e.g., styrene-acrylonit rylecopolymer resins blended with butadiene-acrylonit rile rubbers.

Allyl ResinA synthet ic resin formed by the polymerizat ion of chemical compoundscontaining the group CH2=CH-CH2-. The principal commercial allyl resin is acast ing material that yields allyl carbonate polymer.

Alpha-celluloseVery pure cellulose prepared by special chemical t reatment .

AmineAny of a class of organic compounds derived f rom ammonia by replacementof hydrogen with one or more alkyl groups.

AmorphousLat in meaning without form. Non-crystalline st ructure.

Amorphous PhaseDevoid of crystallinit y – no def inite order. At processing temperatures, theplast ic is normally in the amorphous state.

Angle PressA hydraulic molding press equipped with horizontal and vert ical rams, andspecially designed for the product ion of complex moldings containing deepundercuts.

AnnealTo prevent the format ion of or remove st resses in plast ics by cooling f rom asuitable temperature.

AnnealingA process of holding a material at a temperature mean, but below it s melt ingpoint , the object ive being to permit st ress relaxat ion without distort ion ofshape. It is of ten used on molded art icles to relieve st resses set up by f lowinto the molds.

Anti-f riction CompoundsMaterials specif ically formulated to reduce or eliminate f rict ion.

AntifoggerAn addit ive that prevents condensat ion of moisture on glass and othert ransparent materials, such as windshields or lenses.

Antioxidants & AntiozonantsThese addit ives are used to prevent the negat ive ef fects of oxygen andozone on the resin materials.

Antistatic AgentsMethods of minimizing stat ic elect ricit y in plast ic materials. Such agents areof two basic t ypes: (1) metallic devices which come into contact with theplast ics and conduct the stat ic to earth. Such devices give complete

neut ralizat ion at the t ime, but because they do not modify the surface of thematerial it can become prone to further stat ic during subsequent handling; (2)chemical addit ives which, mixed with the compound during processing, give areasonable degree of protect ion to the f inished products.

AramidAny of a group of lightweight by very st rong heat -resistant synthet ic aromat icpolyamide materials that are fashioned into f ibers, f ilaments, or sheets.

Arc1) A luminous glow formed by the f low of elect ric current through ionized air,gas or vapor between separated elect rodes or contacts. 2) A port ion of thecircumference of a circle.

Arc Resistance1) The resistance to the f low of current of fered by the voltaic arc (i.e., if t hecarbons of an arc lamp are 1/32″ apart , the arc resistance will be 1-1/2 ohms).2) The resistance of a material to the ef fects of an arc passing across it ssurface stated as a measure of the total elapsed t ime taken to form aconduct ing path (of material carbonizing by the arc f lame) across the surfaceunder prescribed condit ions of applicat ions of a high voltage, low current arc(as across an insulator).

Aromatic HydrocarbonsHydrocarbons derived f rom or characterized by presence of unsaturatedresonant ring st ructures.

AsbestosA gray, non-burning, non-conduct ive and chemical resistant material occurringin long f ibers or f ibrous masses, somet imes used as a f iller for reinforcement .

AtacticA polymer exhibit ing no stereochemical regularit y of st ructure.

Autoclave MoldingModif icat ion of the pressure bag method for molding reinforced plast ics. Af terlay-up, ent ire assembly is placed in steam autoclave at 50 to 100 psi.Addit ional pressure achieves higher reinforcement loadings and improvedremoval of air.

Automatic moldA mold for inject ion or compression molding that repeatedly goes through theent ire cycle, including eject ion, without human assistance.

Average Molecular Weight (viscosity method)The molecular weight of polymeric materials determined by the viscosit y ofthe polymer in solut ion at a specif ic temperature. This gives an averagemolecular weight of the molecular chains in the polymer independent ofspecif ic chain length. Falls between weight average and number average

molecular weight .

AWGAbbreviat ion for American Wire Gauge, a standard system for designat ingwire diameter.

B-stageThis describes an intermediate stage of react ion where the material willsof ten when heated and swells in the presence of certain liquids, but may notcompletely fuse or dissolve. The resin is usually supplied in this uncured state.

Back PressureThe viscosit y resistance of a material to cont inued f low when a mold isclosing. In ext rusion, the resistance to the forward f low of molten material.

Backing PlateIn inject ion molding, a plate used as a support for the cavit y blocks, guide pins,bushings, etc.

Baf f leA device used to rest rict or divert the passage of f luid through a pipe line orchannel. In hydraulic systems the device, which of ten consists of a disc with asmall cent ral perforat ion, rest ricts the f low of hydraulic f luid in a high pressureline. A common locat ion for the disc is in a joint in the line. When applied tomolds, the term is indicat ive of a plug or similar device located in a steam orwater channel in the mold and designed to divert and rest rict the f low to adesired path.

Bag moldingA method of applying pressure during bonding or molding, in which a f lexiblecover, usually in connect ion with a rigid die or mold, exerts pressure on thematerial being molded, through the applicat ion of air pressure or drawing of avacuum.

BakeliteThe proprietary name for phenolic and other plast ics materials produced byBakelite Limited, but of ten used indiscriminately to describe any phenolicmolding material or molding. The name is derived f rom that of Dr. Leo HendrikBaekeland (1863-1944), a Belgian who, through his work on synthesis ofphenolic resins and their commercial development in the early 1900’s, isgenerally considered to be the “father” of the plast ic indust ry.

BaseThe material woven (such as paper, woven cot ton, glass fabric, or glass f ibermat , felted asbestos, aramid f ibers, graphite and nylon fabrics) in the form ofsheets or rolls which can be impregnated with resin to form laminated plast ics.

Benzene RingThe basic st ructure of benzene, the most important aromat ic chemical. It is

an unsaturated, resonant 6-carbon ring having three double bonds. One ormore of the 6 hydrogen atoms of benzene may be replaced by other atomsor groups.

BinderThe organic or inorganic material which encapsulates and holds together thebase in reinforced or otherwise heterogeneous composites.

Biocides & FungicidesThese addit ives act as pest icides and are used to inhibit the growth of fungusand other pests.

BleedTo give up color when in contact with water or a solvent ; undesired movementof certain materials in a plast ic (e.g. plast icizers in vinyl) to the surface of thef inished art icle or into an adjacent material. Also called Migrat ion.

BlisterA raised area on the surface of a molding caused by the pressure of gasesinside it on it s incompletely hardened surface.

Block CopolymerAn essent ially linear copolymer in which there are repeated sequences ofpolymeric segments of dif ferent chemical st ructure.

Blocking & Anticaking AgentsThese addit ives are used to prevent the adhesion of two touching layers off ilm during fabricat ion and storage.

BloomA visible exudat ion or ef f lorescence on the surface of a material.

Blow MoldingMethod of fabricat ion in which a warm plast ic parison (hollow tube), is placedbetween the two halves of a mold cavit y and forced to assume the shape ofthat mold cavit y by use of air pressure.

Blow moldingA method of fabricat ion in which a parison (hollow tube) is forced into theshape of the mold cavit y by internal air pressure.

Blow PressureThe air pressure used to form a hollow part by blow molding.

Blow RateThe speed at which the air enters the parison during the blow loading cycle.

Blowing & Foaming AgentsUpon addit ion to plast ics or rubbers and then heat ing, this chemical generatesinert gases which result s in the resin assuming a cellular st ructure.

Blown TubingA thermoplast ic f ilm which is produced by ext ruding a tube, applying a slightinternal pressure to the tube to expand it while st ill molten and subsequentcooling to set the tube. The tube is then f lat tened through guides and woundup f lat on rolls. The size of blown tubing is determined by the f lat width ininches as wound rather than by the diameter as in the case of rigid t ypes oftubing.

Blowup RatioIn blow molding, the rat io of the mold cavit y diameter to the parison diameter.In blown tubing (f ilm), the rat io of the f inal tube diameter (before gusset ing, ifany) to the original die diameter.

Bond Strength1)The measure of the force required to separate objects or materials bondedtogether. 2) The st rength of the bond between f iber and mat rix. 3) Thedegree of at t ract ion between adjacent atoms within a molecule, usuallyexpressed in J/mol.

BossProtuberance on a plast ic part designed to add st rength, to facilit atealignment during assembly, to provide for fastening, etc.

Boston RoundA part icular shape of container; cross sect ion as well as shoulders are round.

Bottom BlowA specif ic t ype of blow molding machine which forms hollow art icles byinject ing the blowing air into the parison f rom the bot tom of the mold.

Bottom PlatePart of the mold which contains the heel radius and the push-up.

BranchedIn molecular st ructure of polymers (as opposed to Linear), refers to sidechains at tached to the main chain. Side chains may be long or short .

BreakdownThe disrupt ive discharge through insulat ion due to failure under elect rostat icst ress.

Breaker PlateA perforated plate located at the rear end of an ext ruder head. It of tensupports the screens that prevent foreign part icles f rom entering the die.

BreathingThe opening and closing of a mold to allow gases to escape early in themolding cycle. Also called Degassing. When referring to plast ic sheet ing,“breathing” indicates permeabilit y to air.

BrightenersAre used to add smoother or brighter coat ings.

British Thermal Unit (BTU)The quant it y of heat required to raise the temperature of one pound of water1°F f rom 58.5 to 59.5°F (it s point of maximum densit y).

Brittle TemperatureA measure for judging the relat ive merit s of materials for low temperaturef lexing or impact – i.e., the temperature at which materials rupture by impactunder specif ied condit ions.

Bubbler mold Cooling (injection molding)A method of cooling an inject ion mold in which a st ream of cooling liquid f lowscont inuously into a cooling out let normally posit ioned at the end opposite theinlet . Uniform cooling can be achieved in this manner.

Bulk DensityASTM D1182-54 test method describes this measurement of mass per unitvolume of a molding powder (in large volume determinat ions).

Bulk DensityThe mass per unit volume of a molding powder as determined in a reasonablylarge volume. The recommended test method is ASTM D1182-54.

Bulk FactorRat io of the volume of loose molding powder to the volume of the sameweight of resin af ter molding.

Bulk-molding compounds (BMC)Bulk-molding compounds are used as a premix in composite manufacturing. ABMC consists of a mixture of resin, reinforcements, inert f illers, and otheraddit ives which form a put tylike preformed shape, rope or sheet .

Bushing (extrusion)The outer ring of any type of a circular tubing or pipe die which forms theouter surface of the tube or pipe.

ButadieneA gas, insoluble in water but soluble in alcohol and ether, obtained f rom thecracking of pet roleum, f rom coal tar benzene or f rom acetylene producedf rom coke and lime. It is widely used in the format ion of copolymers withstyrene, acrylonit rile, vinyl chloride and other monomeric substances, where itimparts f lexibilit y to the subsequent moldings.

Butadiene Styrene PlasticsA synthet ic resin derived f rom the copolymerizat ion of butadiene gas andstyrene liquids.

Buttress ThreadA type of threading in which the thread sides terminate abrupt ly in threadinggradually tapering down to the neck f inish. Designed to withstand maximumforce in one direct ion only. Cross sect ion of thread is t riangular.

Butylene PlasticsPlast ics based on resins made by the polymerizat ion of butene orcopolymerizat ion by butene with one or more unsaturated compounds, thebutene being in greatest amount by weight .

C-stageThis term describes the f inal stage of the react ion where the material srelat ively insoluble and infusible.

CalenderingA form of ext rusion using two or more counter rotat ing rolls in which f ilm andsheet is produced by squeezing a hot , viscous material between them.

CanvasA cot ton fabric weighing more than four ounces per square yard. (Used as thebase material for NEMA grades C, CE and some L grade laminates.)

CapacitanceThe property of an elect ric nonconductor that permits the storage of energyas a result of the separat ion of charge that occurs when opposite surfaces ofthe nonconductor are maintained at a dif ference of potent ial.

Carbon BlackA black pigment produced by the incomplete burning of natural gas or oil. It iswidely used as f iller, part icularly in the rubber indust ry. Because it possessesuseful ult raviolet propert ies. It is also used in polyethylene compoundsintended for such applicat ions as cold water piping and black agriculturalsheet .

CarbonylOrganic funct ional group occurring in aldehydes, ketones, carboxylic acids,esters and their derivat ives.

CastTo form a “plast ic” object by pouring a f luid monomer-polymer solut ion into anopen mold where it f inishes polymerizing. (2) Forming plast ic f ilm and sheet bypouring the liquid resin onto a moving belt or by precipitat ion in a chemicalbath.

Cast FilmA cast f ilm is made by deposit ing a layer of plast ic onto a surface thensolidif ying and removing the f ilm f rom that surface. The plast ic layer can be inmolten form, in a solut ion, or in dispersion.

CatalystA substance which markedly speeds up the cure of a compound when addedin minor quant it y as compared to the amounts of primary reactants.

CavityDepression in a mold made by cast ing, machining, hobbing, or a combinat ionof these methods; depending on number of such depressions, molds aredesignated as Single-Cavit y or Mult i-Cavit y.

Cellular PlasticsPlast ics containing numerous small cavit ies (cells), interconnect ing or notdist ributed throughout the mass.

CelluloidA thermoplast ics material made by the int imate blending of cellulose nit ratewith camphor. Alcohol is normally employed as a volat ile solvent to assistplast icizat ion, and is subsequent ly removed.

CelluloseA natural high polymeric carbohydrate found in most plants; the mainconst ituent of dried woods, jute, f lax, hemp, ramie, etc. Cot ton is almost purecellulose.

Cellulose PropionateAn ester of cellulose made by the act ion of propionic acid and it s anhydride onpurif ied cellulose. It is used as the basis of a thermoplast ic molding material.

Cellulose TriacetateA cellulosic material made by react ing purif ied cellulose with acet ic anhydridein the presence of a catalyst . It is used in the form of f ilm and f ibers. Films andsheet are cast f rom clear solut ions on to “drums” with highly polishedsurfaces. The f ilm, which is of excellent clarit y, has high tensile st rength, andgood heat resistance and dimensional stabilit y. Applicat ions include bookjackets, magnet ic recording tapes, and various types of packaging. Celluloset riacetate sheet has somewhat similar propert ies to those of the f ilm and isused to make such art icles as safety goggles, map wallets and t ransparentcovers of many kinds.

CelsiusAlso referred to as Cent igrade, is equal to the dif ference between thetemperature in Fahrenheit less 32 and the quant it y divisible by 1.8°C = (°F –32) ÷ 1.8.

CementA dispersion of “solut ion” of unvulcanized rubber or a plast ic in a volat ilesolut ion. This meaning is peculiar to plast ics and rubber indust ries and maynot be an adhesive composit ion.

Center Gated mold

An inject ion mold wherein the cavit y is f illed with resin through an orif iceinterconnect ing the nozzle and the center of the cavit y area. Normally, thisorif ice is located at the bot tom of the cavit y when forming items such ascontainers, tumblers, bowls, etc.

Centrifugal CastingA method of forming thermoplast ic resins in which the granular resin is placedin a rotatable container, heated to molten condit ion by the t ransfer of heatthrough the walls of the container, and rotated so that the cent rifugal forceinduced will f orce the molten resin to conform to the conf igurat ion of theinterior surface of the container. Used to fabricate large diameter pipes andsimilar cylindrical it ems.

ChalkingA powdery residue on the surface of a material of ten result ing f romdegradat ion.

ChargeThe measurement or weight of material used to load a mold at one t ime orduring one cycle.

Chlorinated Polyvinyl Chloride PlasticsPlast ics based on chlorinated polyvinyl chloride in which the chlorinatedpolyvinyl chloride is in the greatest amount of weight .

Chlorof luorocarbon PlasticsPlast ics based on polymers made with monomers composed of chlorine,f luorine, and carbon only.

Chromium PlatingAn elect rolyt ic process that deposit s a hard f ilm of chromium metal ontoworking surfaces of other where resistance to corrosion, abrasion, and/orerosion is needed

CircuitIn f ilament winding, the winding produced by a single revolut ion of mandrel orform.

Clamping PlateA plate f it ted to a mold and used to fasten the mold to a molding machine.

Clamping PressureIn inject ion molding and in t ransfer molding, the pressure which is applied tothe mold to keep it closed, in opposit ion to the f luid pressure of thecompressed molding material.

Clarif ierAn addit ive that increases the t ransparency of a material.

Co-extrusion

The process of combining two or more layers of ext rudate to produce amult iple layer product in a single step.

CoalesceTo combine into one body or to grow together.

Coef f icient of Expansion .The f ract ional change in length (somet imes volume, specif ied) of a materialfor a unit change in temperature. Values for plast ics range f rom 0.01 to 0.2mils/in., C

Coef f icient of FrictionStat ic: the rat ion of the limit ing f rict ion developed to the corresponding normalpressure if two surfaces move relat ive to each other.

Coef f icient of Thermal ExpansionThe unit change in dimension of a material for a unit change in temperature.

Cold Flow or CreepA t ime-dependent st rain of solids result ing f rom st ress.

Cold MoldingThe process of compression molding involving shaping an unheatedcompound in a mold under pressure then heat ing the art icle to cure it .

Cold Slug WellSpace provided direct ly opposite the spruce opening in an inject ion mold tot rap the cold slug.

Cold StretchPulling operat ion, usually on ext ruded f ilaments, to improve tensile propert ies.

Colorants & PigmentsAre addit ive used to change the color of the plast ic. They can be a powder ora resin/color premix.

Composite1)A st ructure or an ent it y made up of dist inct components. 2) A complexmaterial, such as f iberglass, in which two or more dist inct , st ructurallycomplementary substances, especially glasses and polymers, combine toproduce st ructural or funct ional propert ies not present in any individualcomponent . 3) Reinforced laminates (i.e., canvas phenolic, glass epoxy, etc.).

CompoundThese are chemical combinat ions of materials which include all the materialsnecessary for the f inished product . They include BMC (Bulk MoldingCompounds), SMC (Sheet Molding Compounds) and TMC (Thick MoldingCompounds).

Compression Molding

The process of molding a material in a conf ined shape by applying pressureand usually heat .

Compression RatioIn an ext ruder screw, the rat io of volume available in the f irst f light at thehopper to the last f light at the end of the screw.

Compressive StrengthThe abilit y of a material to resist a force that tends to crush it .

ConcentricityFor a container, the shape in which various cross sect ions have a commoncenter.

CondensationA chemical react ion in which two or more molecules combine with theseparat ion of water or some other simple substance. If a polymer is formed,the condensat ion process is called Polycondensat ion. See alsoPolymerizat ion.

ConditioningThe subject ion of a material to a st ipulated t reatment so that it will respond ina uniform way to subsequent test ing or processing. The term is f requent lyused to refer to the t reatment given to specimens before test ing.

ConductivityThe reciprocal of volume resist ivit y. It is the conductance of a unit cube of anymaterial.

ConductorA wire, or combinat ion of wires not insulated f rom each other, suitable forcarrying elect ricit y.

Continuous Service TemperatureThe highest temperature at which a material can perform reliably in long termapplicat ion – long term being, however, inconsistent ly def ined by themanufacturers.

Convergent DieA die in which the internal channels leading to the orif ice are converging (onlyapplicable to dies for hollow bodies).

ConveyorA mechanical device to t ransport material f rom one point to another, of tencont inuously.

Cooling ChannelsChannels or passageways located within the body of a mold through which acooling medium can be circulated to cont rol temperature on the mold surface.

Cooling FixtureBlock of metal or wood holding the shape of a molded piece which is used tomaintain the proper shape or dimensional accuracy of a molding af ter it isremoved f rom the mold unt il it is cool enough to retain it s shape withoutfurther distort ion. Also known as Shrink Fixture.

CopolymerThe chemical react ion of two dif ferent monomers with each other, result in acompound.

Copper Clad LaminateLaminates (i.e., FR4) having copper foil bonded to one or both surfaces andintended primarily for use in printed circuit s.

CoreThe cent ral member of a sandwich const ruct ion (can be honeycomb material,foamed plast ic, or solid sheet ) to which the face of the sandwich areat tached; the cent ral member of a plywood assembly. (2) A channel in a moldfor circulat ion of heat -t ransfer media. (3) Part of a complex mold that moldsundercut parts. Cores are usually withdrawn to one side before the mainsect ions of the mold open. Also called Core Pin.

Core DrillA device for making cooling channels in a mold.

Corona ResistanceA current passing through a conductor induces a surrounding elect rostat icf ield. When voids exist in the insulat ion near the conductor, the high voltageelect rostat ic f ield may ionize and rapidly accelerate some of the airmolecules, ionizing them, and thereby “eat ing” a hole in the insulat ion.Resistance to this process is called corona resistance.

CorrosionChemical act ion which causes dest ruct ion of the surface of a material byoxidat ion or chemical combinat ion. Also caused by reduct ion of the elect ricalef f iciency between a metal and a cont iguous substance or to thedisintegrat ing ef fects of st rong elect rical currents or ground return currents inelect rical systems. The lat ter is known as elect rolyt ic corrosion.

Corrosion ResistanceThe abilit y to withstand the ef fect of oxidat ion.

Coupling AgentsA material that is used to form a chemical bridge between the resin and glassf iber or mineral f iber. By act ing as an interface, bonding is enhanced.

CraterA small, shallow surface imperfect ion.

CrazingSmall cracks near or on the surface of plast ic materials.

CrazingFine cracks which may extend in a network on or under the surface or througha layer of a plast ic material.

CreepThe dimensional change with t ime of a material under load. At roomtemperature it is also called cold f low.

Cross LaminateA laminate in which some of the layers of material are oriented approximatelyat right angles to the remaining layers with respect to the grain or st rongestdirect ion in tension.

Cross-linkingThe format ion of chemical links between the molecular chains in polymers.This process can be achieved by chemical react ion, vulcanizat ion, andelect ron bombardment .

Crosshead (extrusion)A device generally employed in wire coat ing which is at tached to thedischarge end of the ext ruder cylinder, designed to facilit ate ext rudingmaterial at an angle. Normally, this is a 90 degree angle to the longitudinal axisof the screw.

CrystallinityA molecular st ructure result ing f rom the format ion of solid crystals with ageomet ric pat tern.

CullMaterial remaining in a t ransfer chamber af ter mold has been f illed. Unlessthere is a slight excess in the charge, the operator cannot be sure cavit y isf illed. Charge is generally regulated to cont rol thickness of cull.

CureThe process of changing propert ies of polymer into a more stable and usablecondit ion. This is accomplished by the use of heat , radiat ion, or react ion withchemical addit ives.

Cure CycleThe t ime periods at def ined condit ions to which a react ing thermoset t ingmaterial is processed to reach a desired property level.

Curing TemperatureTemperature at which a cast , molded, or ext ruded product , a resin-impregnated reinforcing material, an adhesive, etc., is subjected to curing.

Curing T ime

The period of t ime that a react ing thermoset t ing material is exposed tospecif ic condit ions to reach a specif ied property level.

Curtain CoatingA method of coat ing which may be employed with low viscosit y resins orsolut ions, suspensions, or emulsions of resins in which the subst rate to becoated is passed through and perpendicular to a f reely falling liquid “curtain”(or “waterfall”). The f low rate of the falling liquid and the linear speed of thesubst rate passing through the curtain are co-ordinated in accordance with thethickness of coat ing desired.

CurvatureA condit ion in which the parison is not st raight , but somewhat bending andshif t ing to one side, leading to a deviat ion f rom the vert ical direct ion ofext rusion. Centering of ring and mandrel can of ten relieve this defect .

Cut-of fThe line where the two halves of a compression mold come together; alsocalled Flash Groove or Pinch-of f .

CycleThe complete, repeat ing sequence of operat ions in a process of part of aprocess. In molding, the cycle t ime is the period, or elapsed t ime, between acertain point in one cycle and the same point in the next .

CylindricalRefers to the shape of a container which has a circular cross sect ion parallelto the minor axis and a rectangular cross sect ion parallel to the major axis.

Dash-potA device used in hydraulic systems for damping down vibrat ion. It consists ofa piston at tached to the part to be damped and f it ted into a vesselcontaining f luid or air. It absorbs shocks by reducing the rate of change in themomentum of moving parts of machinery.

Daylight OpeningClearance between two platens of a press in the open posit ion.

Deckle RodA small rod, or similar device, inserted at each end of the ext rusion coat ing diewhich is used to adjust the length of the die opening.

Decomposition ProductThe const ituent elements or simpler compounds formed when a substancedecays or decomposes.

Decorative SheetA laminated plast ics sheet used for decorat ive purposes in which the colorand/or surface pat tern is an integral part of the sheet .

Def lashingCovers the range of f inishing techniques used to remove the f lash (excess,unwanted material) on a plast ic molding.

Def lection TemperatureThe measure of temperature at which a specimen def lects 0.01 inches undera load of 264 lb/in2.

Degree of PolymerizationThe number of st ructural unit s or mers in the “average” polymer molecule in apart icle sample. In most plast ics the DP must reach several thousand ifworthwhile physical propert ies are to be had.

DelaminationThe separat ion of a laminate along the plane of it s layers. Also the separat ionof bonded insulat ion within the adhesive layer or at the adhesive interface.

DeliquescentCapable of at t ract ing moisture f rom the air.

DensityThe equivalent property to specif ic gravit y; measured by displacement .

DesiccantSubstance which can be used for drying purposes because of it s af f init y forwater

Die GapThe distance between the metal faces forming the die opening.

Die LinesVert ical marks on the parison caused by damage of die parts orcontaminat ion.

Die Swell RatioThe rat io of the outer parison diameter (or parison thickness) to the outerdiameter of the die (or die gap). Die swell rat io is inf luenced by polymer t ype,head const ruct ion, land length, ext rusion speed, and temperature.

Dielectric1) Any insulat ing medium which intervenes between two conduit s and permitselect rostat ic at t ract ion or repulsion to take place across is. 2) A materialhaving the property that energy required to establish an elect ric f ield isrecoverable in whole or in part , as elect ric energy (see insulat ion forclarif icat ion).

Dielectric ConstantThe rat io of the capacit y of a condenser made with a part icular dielect ricmaterial to the capacit y of the same condenser with air as the dielect ric.Measured at a f requency of 106 cycles per second.

Dielectric Constant (Permittivity or Specif ic Inductive Capacity)The specif ic induct ive capacit y of a dielect ric. That property of a dielect ricwhich determines the elect rostat ic energy stored per unit volume for unitpotent ial gradient .

Dielectric Heating (Electronic Heating)The plast ic to be heated forms the dielect ric of a condenser to which isapplied a high-f requency (20 to 80 mc.) voltage. Dielect ric loss in the materialis the basis. Process used for sealing vinyl f ilms and preheat ing thermosetmolding compounds.

Dielectric StrengthThe voltage that an insulat ing material can withstand before dielect ricbreakdown occurs.

Dielectric StrengthAbilit y to retain precise shape and size.

Dimensional StabilityAbilit y of a plast ic part to retain the precise shape in which it was molded,fabricated, or cast .

Dip CoatingApplying a plast ic coat ing by dipping the art icle to be coated into a tank ofmelted resin or plast isol, then chilling the adhering melt .

DiscolorationAny change f rom the original color, of ten caused by overheat ing, lightexposure, irradiat ion, or chemical at tack.

DispersionFinely divided part icles of a material in suspension in another substance.

DissipationUnusable or lost energy, as the product ion of heat in a circuit .

Dissipation FactorThe rat io of the power dissipated in wat ts in an insulat ing material to theproduct of the ef fect ive voltage and the current . Measured at a f requency of106 cycles per second.

Divergent DieA die in which the internal channels leading to the orif ice are diverging(applicable only to dies for hollow bodies).

DomeIn reinforced plast ics, an end of a f ilament wound cylindrical container.

Double-shot molding

A means of turning out two-color parts in thermoplast ics materials bysuccessive molding operat ions.

Draf tThe degree of taper of a side wall or the angle of clearance designed tofacilit ate removal of parts f rom a mold.

Drape Assist FrameIn sheet thermoforming, a f rame (made up of anything f rom thin wires to thickbars) shaped to the peripheries of the depressed areas of the mold andsuspended above the sheet to be formed. During forming, the assist f ramedrops down, drawing the sheet t ight ly into the mold and thereby prevent ingwebbing between high areas of the mold and permit t ing closer spacing inmult iple molds.

Drape Forming

Method of forming thermoplast ic sheet in which the sheet is clamped into amovable f rame, heated, and draped over high points of a male mold. Vacuumis then pulled to complete the forming operat ion.

Draw Down Ratio

The rat io of the thickness of the die opening to the f inal thickness of theproduct .

DrawingThe process of st retching a thermoplast ic sheet or rod to reduce it s cross-sect ional area.

Dry ColoringMethod commonly used by fabricators for coloring plast ics by tumble blendinguncolored part icles of the plast ic material with selected dyes and pigments.

Dry Strength

The st rength of an adhesive joint determined immediately af ter drying underspecif ied condit ions or af ter a period of condit ioning in the standardlaboratory atmosphere. See Wet St rength.

Dry-blendA f ree-f lowing dry compound prepared without f luxing or addit ion of solvent .Also called powder blend.

DuctilityThe extent to which a solid material can be drawn into a thinner cross sect ion.

DwellA pause in the applicat ion of pressure to a mold, made just before the mold iscompletely closed, to allow the escape of gas f rom the molding material.

DyesSynthet ic or natural organic chemicals that are soluble in most commonsolvents. Characterized by good t ransparency, high t inctorial st rength, andlow specif ic gravit y.

Ef fect of Strong AcidsA descript ive notat ion to indicate the material’s performance.

Ef fective Thread TurnsThe number of full 360 degree turns on a threaded closure that are actually incontact with the neck thread.

Ejector Pin (on Sleeve)A pin or thin plate that is driven into a mold cavit y f rom the rear as the moldopens, forcing out the f inished pieces. Also Knockout Pin.

Ejector Return PinsProject ions that push the ejector assembly back as the mold closes; alsocalled Surface Pins and Return Pins.

Ejector RodBar that actuates the ejector assembly when mold is opened.

Elastic DeformationThe part of the deformat ion of an object under load which is recoverablewhen the load is removed.

ElastomerA material which at room temperature st retches under low st ress to at leasttwice it s length and snaps back to the original length upon release of st ress.See also Rubber.

Electroformed MoldsA mold made by elect roplat ing metal in the reverse pat tern on the cavit y.Molten steel may be then sprayed on the back of the mold to increase it sst rength.

Electronic TreatingA method of oxidizing a f ilm of polyethylene to render it printable by passingthe f ilm between the elect rodes and subject ing it to a high voltage coronadischarge.

ElectroplatingThe deposit ion of a layer of metal on a base of metal or conduct ing surfaceby elect rolysis.

ElongationThe f ract ional increase in length of a material st ressed in tension.

EmbossingTechniques used to create depressions of a specif ic pat tern in plast ics f ilmand sheet ing.

EmulsionA suspension of f ine droplets of one liquid in another.

EncapsulatingEnclosing an art icle (usually an elect ronic component or the like) in a closedenvelope of plast ic, by immersing the object in a cast ing resin and allowing theresin to polymerize or, if hot , to cool.

Endothermic ReactionA chemical react ion in which heat is absorbed.

Entrance AngleMaximum angle at which the molten material enters the land area of the die,measured f rom the center line of the mandrel.

Environmental Stress CrackingThe suscept ibilit y of a thermoplast ic art icle to crack or craze format ion underthe inf luence of certain chemicals and st ress.

Epoxy ResinsSt raight -chain thermoset t ing resins containing at least one three-memberedring consist ing of two carbon atoms and one oxygenat ion.

EsterThe react ion product of an alcohol and an acid.

Ethylene PlasticsPlast ics based on polymers of ethylene or copolymers of ethylene with othermonomers, the ethylene being in greatest amount by mass.

Ethylene-vinyl AcetateCopolymers f rom these two monomers form a new class of plast ic materials.They retain many of the propert ies of polyethylene, but have considerablyincreased f lexibilit y for their densit y – elongat ion and impact resistance arealso increased.

ExothermThe temperature/t ime curve of a chemical react ion giving of f heat , part icularlythe polymerizat ion of cast ing resins. (2) The amount of heat given of f . Theterm has not been standardized with respect to sample size, ambienttemperature, degree of mixing, etc

Exothermic ReactionA chemical react ion in which heat is evolved.

Extender

A material added to a plast ic compound used to reduce the amount of resinrequired per unit value.

ExtrudateThe product or material delivered by an ext ruder, such as f ilm, pipe, thecoat ing on wire, etc.

ExtrusionThe process of forming a cont inuous piece of plast ic by forcing it through ashaping orif ice with or without the presence of heat .

ExtrusionThe method of processing plast ic by forcing heat sof tened plast ic through anopening of the desired shape of the cross-sect ion of the f inished product .

Fabric-Base LaminateLaminated insulat ing material formed by bonding woven cloth (of f iberglass,cot ton or synthet ic f ibers) with resin under heat and pressure.

FabricatingThe manufacture of plast ic products by appropriate operat ions. This includesplast ics formed into molded parts, rods, tubes, sheet ing, ext rusion and otherforms by methods including punching, cut t ing, drilling, tapping, fastening or byusing other mechanical devices.

FahrenheitEquals 1.8 mult iplied to the sum of the temperature in Celsius and °F = 1.8 x(°C + 32).

Family Mold (injection)A mult i-cavit y mold where each of the cavit ies forms one of the componentparts of the assembled f inished object .

FiberA thread or threadlike st ructure such as cellulose, wool, silk or glass yarn.

Fiber ShowSt rands or bundles of f ibers that are not covered by resin and that are at orabove the surface of a reinforced plast ic.

Fibre1) A specif ic form of chemically jelled f ibrous materials manufactured insheets, rods and tubes. 2) Commonly used interchangeably with f iber.

Filament1) Fiber characterized by ext reme length. 2) The resistance wire through whichf ilament current is sent in a thermionic tube to produce the heat required forelect ron emissions.

Filament Winding

Resin impregnated robbing or single st rands of glass or other reinforcementwound in a pre-determined pat tern onto a suitable form or mandrel and thencured.

Fill PointThe level to which a container must be f illed to furnish a designated quant it yof the content .

Fill-and-WipeParts are molded with depressed designs; af ter applicat ion of paint , surplus iswiped of f , leaving paint remaining only in the depressed areas.

FillerA cheap, inert substance added to a plast ic to make it less cost ly. Fillers mayalso improve physical propert ies, part icularly hardness, st if fness, and impactst rength. The part icles are usually small, in cont rast to those ofreinforcements but there is some overlap between the funct ion of the two.

Fillers & ReinforcementsFillers are used to make a resin less cost ly. They can be inert or they can altersome propert ies of the plast ic. Reinforcements are substances used tost rengthen or give dimensional stabilit y to a material.

FilletA rounded f illing of the internal angle between two surfaces of a plast icmolding.

FilmFilms are f lat materials that are ext remely thin in comparison to it s length andbreadth. Typically, a f ilm has a maximum nominal thickness of 0.25 millimeters.

FinThe web of material remaining in holes or openings in a molded part whichmust be removed in f inishing.

FinishThe plast ic forming the opening of a container shaped to accommodate aspecif ic closure. Also, the ult imate surface of an art icle.

Finish InsertA removable part of a blow mold to form a specif ic neck of a plast ic bot t le.Somet imes called Neck Insert .

Fish EyeA fault in t ransparent or t ranslucent plast ics materials, such as f ilm or sheet ,appearing as a small globular mass and caused by incomplete blending of themass with surrounding materials.

FishPaper1) A type of vulcanized f ibre paper t reated chemically for insulat ing purposes

where high mechanical and elect rical st rength and f lexibilit y are required. 2) Avulcanized f ibre in thin cross-sect ion.

FlakeUsed to denote the dry, unplast icized base of cellulosic plast ics.

Flame Retardant ResinA resin which is compounded with certain chemicals to reduce or eliminate it stendency to burn. For polyethylene and similar resins, chemicals such asant imony t rioxide and chlorinated paraf f ins are useful.

Flame SprayingMethod of applying a plast ic coat ing in which f inely powdered f ragments ofplast ic, together with suitable f luxes, are projected through a cone of f lameonto a surface.

Flame TreatingA method of rendering inert thermoplast ic objects recept ive to inks, lacquers,paints, adhesives, etc. in which the object is bathed in an open f lame topromote oxidat ion of the surface of the art icle.

Flame, Fire & Smoke RetardantsAre added to the resin to retard these undesirable ef fects.

FlammabilityMeasure of the extent to which a material will support combust ion.

FlangeA rib or rim for st rength, for guiding, or for at tachment to a pipe.

FlashExt ra plast ic at tached to a molding along the part ing line; it must be removedbefore the part can be considered f inished.

Flash GateWide gate extending f rom a runner which runs parallel to an edge of a moldedpart along the part ing line of a mold.

Flash GateA long, shallow rectangular gate

Flash LineA raised line appearing on the surface of a molding and formed at the junct ionof mold faces.

Flash moldA mold designed to permit excess molding material to escape during closing.

Flash PointThe lowest temperature at which a f lammable liquid will produce a

combust ible vapor that will burn in the presence of a f lame, under certainprescribed condit ions of test .

Flexible MoldsMolds made of rubber or elastomeric plast ics used for cast ing plast ics. Theycan be st retched to remove cured pieces with undercuts.

Flexural ModulusThe rat io, within the elast ic limit , of the applied st ress on a test specimen inf lexure to the corresponding st rain in the outermost f ibers of the specimen.

Flexural StrengthThe st rength of a material in bending, expressed as the tensile st ress of theoutermost f ibers of a bent test specimen at the instant of failure.

FlockingA method of coat ing by spraying f inely dispersed powders or f ibers.

Flow LineA mark on a molded piece made by the meet ing of two f low f ronts duringmolding. Also called weld line.

Flow MarksWavy surface appearance of an object molded f rom thermoplast ic resinscaused by improper f low of the resin into the mold.

Fluidized Bed CoatingA method of applying a coat ing of a thermoplast ic resin to an art icle in whichthe heated art icle is immersed in a dense-phase f luidized bed of powderedresin and thereaf ter heated in an oven to provide a smooth, pin-hole-f reecoat ing.

Fluorescent PigmentsBy absorbing unwanted wavelengths of light and convert ing them into light ofdesire wavelengths, these colors seem to have an actual glow of their own.

FluorineThe most react ive non-metallic element . A pale yellow gas which is bothcorrosive and poisonous, it reacts vigorously with most oxidizable substancesat room temperature, and forms f luorides. It is used in the product ion ofmetallic and other f luorides, some of which are used to int roduce f luorine intoorganic compounds, i.e., the f luorocarbons.

Fluorocarbon PlasticsPlast ics based on polymers made with monomers composed of f luorine andcarbon only.

Foaming AgentsChemicals added to plast ics and rubbers that generate inert gases onheat ing, causing the resin to assume a cellular st ructure.

Foil DecoratingMolding paper, text ile, or plast ic foils printed with compat ible inks direct ly intoa plast ic part so that the foil is visible below the surface of the part asintegral decorat ion.

Force PlateThe plate that carries the plunger of force plug of a mold and guide pins andbushings. Since it is usually drilled for steam or water lines, it is also called theSteam Plate.

Force PlugThe port ion of a mold that enters the cavit y block and exerts pressure on themolding compound, designated as Top Force or Bot tom Force by posit ion inthe assembly; also called Plunger or Piston.

FormaldehydeA colorless gas (usually employed as a solut ion in water) which possesses asuf focat ing, pungent odor. It is derived f rom the oxidat ion of methanol or low-boiling pet roleum gases such as methane, ethane, propane, and butane. It iswidely used in the product ion of phenol formaldehyde (phenolic), ureaformaldehyde (urea), and melamine formaldehyde (melamine) resins.

FormingThe process whereby the current shape of a plast ic is t ransformed to anotherdesired conf igurat ion.

Formulation1) A combinat ion of ingredients before processing or made into a f inishedproduct . Also used as a synonym for a material, compound. 2) A select ion ofcomponents of a product formula or mixture to provide opt imum specif icpropert ies for the end-use desired.

Friction Coef f icientA number expressing the amount of f rict ional ef fect .

Furan ResinsDark colored, thermoset t ing resins available primarily as liquids ranging f romlow-viscosit y polymers to thick, heavy syrups.

GasketPiece used to make a joint f luid-t ight .

GateIn inject ion and t ransfer molding, the orif ice through which the melt enters thecavit y. Somet imes the gate has the same cross-sect ion as the runner leadingto it ; of ten, it is severely rest ricted.

GaylordA large corrugated container usually sized to match the length and width

dimensions of a pallet . Gaylord is actually a t rade name that has becomesynonymous with this specif ic t ype of container.

Glass ClothFabric used as insulat ing material base formed by weaving yarns comprisingglass f ilaments and possessing high st rength, heat resistance and dielect ricpropert ies.

Glass FiberGlass in f ibrous form that has cooled to a rigid condit ion without crystallizing.

Glass ThreadA type of threading in which the thread sides gradually taper down to the neckf inish. Cross sect ion of threads are semi-circular.

Glass TransitionThe reversible change in an amorphous polymer or in amorphous regions of apart ially crystalline polymer f rom (or to) a viscous or rubbery condit ion to (orf rom) a hard and relat ively brit t le one. NOTE – The glass t ransit ion generallyoccurs over a relat ively narrow temperature region and is similar to thesolidif icat ion of a liquid to a glassy state: it is not a phase t ransit ion. Not onlydo hardness and brit t leness undergo rapid changes in this temperature regionbut other propert ies, such as thermal expansion and specif ic heat alsochange rapidly. This phenomenon has been called second order t ransit ion,rubber t ransit ion and rubbery t ransit ion. The word t ransformat ion has alsobeen used instead of t ransit ion. Where more than one amorphous t ransit ionoccurs in a polymer, the one associated with segmental mot ions of thepolymer backbone chain or accompanied by the largest change in propert iesis usually considered to be the glass t ransit ion.

GlossThe shine or luster of the surface of a material.

Graf t CopolymersA chain of one type of polymer to which side chains of a dif ferent t ype areat tached or graf ted (i.e., polymerizing butadiene and styrene monomer at thesame t ime).

Granular StructureNon-uniform appearance of f inished plast ic material due to retent ion of , orincomplete fusion of , part icles of composit ion, either within the mass or on thesurface.

Grit BlastedA surface t reatment of a mold in which steel grit or sand materials are blownto the walls of the cavit y to produce a roughened surface. Air escape f rommold is improved and special appearance of molded art icle is of ten obtainedby this method.

Guide PinsDevices that maintain proper alignment of force plug and cavit y as moldcloses.

GumAn amorphous substance or mixture which, at ordinary temperatures, is eithera very viscous liquid or a solid which sof tens gradually on heat ing, and whicheither swells in water or is soluble in it . Natural gums, obtained f rom the cellwalls of plants, are carbohydrates or carbohydrate derivat ives ofintermediate molecular weight .

GussetA tuck placed in each side of a tube of blown tubing as produced to provide aconvenient square or rectangular package, similar to that of the familiar brownpaper bag or sack, in subsequent packaging.

HardnessThe resistance of a material to compression, indentat ion and scratching.There are several scales, and the data in the book gives both the scale usedand the value on it .

HazeThe cloudy or turbid appearance of an otherwise t ransparent material causedby light scat tered f rom within the specimen or f rom it s surfaces.

Head SpaceThe space between the f ill level of a container and the sealing plane.

Heat ChamberIn inject ion molding, that part of the machine in which the cold feed is reducedto a hot melt . Also Heat ing Cylinder.

Heat Def lection TemperatureThe temperature at which a standard test bar (ASTM D648) def lects 0.010 in.under a stated load of either 66 or 264 psi.

Heat Distortion PointThe temperature in degrees Celsius at which a standard test bar (ASTMD648) def lects .010 in. under a stated load of either 66 or 264 psi, when thetemperature is raised at a specif ic rate of increase.

Heat LossPower dissipated as heat .

Heat SealingA method of joining plast ic f ilms by simultaneous applicat ion of heat andpressure to areas in contact . Heat may be supplied conduct ively ordielect rically.

Heat StabilizersThese addit ives increase the abilit y of the material to withstand the negat iveef fects of heat exposure. They are used to increase the overall servicetemperature of the material.

Heat-Distortion PointThe temperature at which a standard test bar (ASTM D648) def lects 0.010 in.under a stated load of either 66 or 264 psi.

High-Pressure Laminates (molding pressure high)Laminates molded and cured at pressures not lower than 1,000 psi. (Pressuresof 1,000 to 2,500 psi are not uncommon.)

HobA master model in hardened steel used to sink the shape of a mold into asteel block.

HomopolymerA polymer, consist ing of (neglect ing the ends, branch junct ions, and otherminor irregularit ies) a single t ype of repeat ing unit .

HoneycombManufactured product consist ing of sheet metal or a resin impregnated sheetmaterial (paper, f ibrous, glass, etc.) which has been formed into hexagonal-shaped cells. Used as core material for sandwich const ruct ions.

Hoop StressThe force per unit area in the wall of the pipe in the circumferent ial orientat iondue to internal hydrostat ic pressure.

HopperConical feed reservoir into which molding powder is loaded and f rom which itfalls into a molding machine or ext ruder, somet imes through a meteringdevice.

Hopper DryerA combinat ion feeding and drying device for ext rusion and inject ion molding ofthermoplast ics. Hot air f lows upward through the hopper containing the feedpellets.

Hopper LoaderA curved pipe through which molding powders are pneumat ically conveyedf rom shipping drums to machine hoppers.

Hot Gas WeldingA technique of joining thermoplast ic materials (usually sheet ) whereby thematerials are sof tened by a jet of hot air f rom a welding torch, and joinedtogether at the sof tened points. Generally a thin rod of the same material isused to f ill and consolidate the gap.

Hot-runner moldA mold in which the runners are insulated f rom the chilled cavit ies and are kepthot . Part ing line is at gate of cavit y, runners are in separate plate(s), so theyare not , as is the case usually, ejected with the piece.

Hot-stampingEngraving operat ion for market ing plast ics in which roll leaf is stamped withheated metal dies onto the face of the plast ics. Ink compounds can also beused. By means of felt rolls, ink is applied to t ype and by means of heat andpressure, t ype is impressed into the material, leaving the marking compoundin the indentat ion.

HydraulicA system in which energy is t ransferred f rom one place to another by meansof compression and f low of a f luid (e.g., water, oil).

Hydrocarbon PlasticsPlast ics based on resins made by the polymerizat ion of monomers composedof carbon and hydrogen only.

HydrogenationChemical process whereby hydrogen is int roduced into a compound.

HydrolysisChemical decomposit ion of a substance involving the addit ion of water.

HygroscopicTending to absorb moisture.

ImmiscibleDescript ive of two or more f luids which are not mutually soluble.

Impact Bar (specimen)A test specimen of specif ied dimensions which is ut ilized to determine therelat ive resistance of a plast ic to f racture by shock.

Impact Modif iersAre addit ive used to enhance the material’s abilit y to withstand the force ofimpact .

Impact ResistanceRelat ive suscept ibilit y of material to f racture by st ress at high speeds.

Impact StrengthAbilit y to withstand physical shock loading or work required to f racture undershock loading a specif ied test specimen in a specif ied manner.

Impregnate1) To f ill t he voids and interst ices of material with a compound (this does notimply complete f ill or complete coat ing of the surfaces by a hole-f ree f ilm). 2)

The process of thoroughly soaking a material of an open or porous naturewith a resin.

ImpregnationThe process of thoroughly soaking a material such as wood, paper or fabric,with a synthet ic resin so that the resin gets within the body of the material.The process is usually carried out in an impregnator.

Impulse SealingA heat sealing technique in which a pulse of intense thermal energy is appliedto the sealing area for a very short t ime, followed immediately by cooling. It isusually accomplished by using an RF heated metal bar which is cored forwater cooling or is of such a mass that it will cool rapidly at ambienttemperatures.

InertDef icient in act ive propert ies; not af fect ing other substances when in contactwith them such as inert gases not part icipat ing in any fashion in chemicalreact ions. Inf rared – the band of light in the elect romagnet ic spect rum thatlies between the visible light range and the radar range.

Inf ra-redPart of the elect romagnet ic spect rum between the visible light range and theradar range. Radiant heat is in this range, and inf ra-red heaters are used insheet thermoforming.

InhibitorA substance that slows down chemical react ion. Inhibitors are somet imesused in certain t ypes of monomers and resins to prolong storage lif e.

Injection Blow MoldingBlow molding process by which the plast ic parison to be blown is formed byinject ion molding.

Injection MoldingThe process of forming a material by forcing it f rom a heated cylinder, underpressure, through a spruce into a cavit y of a conf ined mold.

Injection molding CycleThe complete t ime cycle of operat ion ut ilized in inject ion molding of an objectincluding inject ion; die close and die open t ime.

Injection Molding PressureThe pressure applied to the cross-sect ional area of the molding cylinder.

Injection RamThe ram which applies pressure to the plunger in the process of inject ionmolding or t ransfer molding.

Insert

An integral part of a plast ics molding consist ing of metal or other materialwhich may be molded into posit ion or may be pressed into the molding af terthe molding is completed.

InstronAn inst rument ut ilized to determine the tensile and compressive propert ies ofmaterial.

InsulationMaterial having a high resistance to the f low of elect ric current , to preventleakage of current f rom a conductor.

Intrinsic ViscosityThe int rinsic viscosit y of a polymer is the limit ing value of inf inite dilut ion of therat io at the specif ic viscosit y of the polymer solut ion to it s concent rate onmoles per lit er.

Ionomer ResinsA polymer which has ethylene as it s major component , but containing bothcovalent and ionic bonds. The polymer exhibit s very st rong interact ion ionicforces. The anions hang f rom the hydrocarbon chain and the react ions aremetallic – sodium, potassium, magnesium. These resins have many of thesame features as polyethylene plus high t ransparency, tenacit y, resilience,and increased resistance to oils, greases and solvents. Fabricat ion is carriedout as with polyethylene.

ISOInternat ional Organizat ion of Standardizat ion.

IsomerOne of two or more compounds, radicals or ions that contain the samenumber of atoms of the same elements by dif fer in st ructural arrangementand propert ies.

Izod Impact TestA test designed to determine the resistance of a plast ics material to a shockloading. It involves the notching of a specimen, which is then placed in the jawsof the machine and st ruck with a weighted pendulum. See also ImpactSt rength.

Izod, Notched, LTThe energy required to break specimens in which there is a v-notch to createan init ial st ress point but measured at low temperature (minus 40°C).

Izod, Notched, RTThe energy required to break specimens in which there is a v-notched tocreate an init ial st ress point .

Jacket

A tough sheath to protect an insulated wire or cable, or to permanent ly grouptwo or more insulated wires or cables.

Jet moldingProcessing technique characterized by the fact that most of the heat isapplied to the material as it passes through the nozzle or jet , rather than in aheat ing cylinder as is done in convent ional processes.

JettingTurbulent f low of resin f rom an undersize gate or thin sect ion into a thickermold sect ion, as opposed to laminar f low of material progressing radially f roma gate to the ext remit ies of the cavit y.

KelvinThe absolute temperature scale (met ric). K = °C + 273.

KirksiteAn alloy of aluminum and zinc used for the const ruct ion of blow molds; itimparts high degree of heat conduct ivit y to the mold.

Kiss-roll CoatingThis roll arrangement carries a metered f ilm of coat ing to the web; at the lineof web contact , it is split with part remaining on the roll, the remainder of thecoat ing adhering to the web.

Knockout PinA device for knocking a cured piece f rom a mold. Also called Ejector Pin.

Kraf t Paper1) Relat ively heavy, high st rength sulfate paper used for elect rical insulat ingmaterial. 2) Paper made f rom sulfate wood pulp, chief ly pinewood chips bydigest ion with a mixture of caust ic soda.

L/D RatioA term used to def ine an ext rusion screw which denotes the rat io of the screwlength to the screw diameter.

Laminar FlowLaminar f low of thermoplast ic resins in a mold is accomplished bysolidif icat ion of the layer in contact with the mold surface that acts as aninsulat ing shell through which molten material f lows to f ill t he remainder of thecavit y.

Laminar FlowLaminar f low of thermoplast ic resins in a mold is accompanied by solidif icat ionof the layer in contact with the mold surface that acts as an insulat ing tubethrough which material f lows to f ill t he remainder of the cavit y. This t ype off low is essent ial to duplicat ion of the mold surface.

Laminate1) (v) – To build up to desired shape or thickness.2) (n) – A material composedof successive layers of material, usually bonded together under heat andpressure.

Land(1) The horizontal bearing surface of a semi posit ive or f lash mold by whichexcess material escapes. See Cut -of f . (2) The bearing surface along the topof the f lights of a screw in a screw ext ruder. (3) The surface of an ext rusiondie parallel to the direct ion of melt f low.

Lattice PatternIn reinforced plast ics, a pat tern of f ilament winding with a f ixed arrangementof open voids.

LeachTo ext ract a soluble component f rom a mixture by the process of percolat ion.

Light TransmissionThe amount of light that a plast ic will allow to pass.

Light, UV Stabilizers & AbsorbersThese addit ives increase the abilit y of the material to withstand the negat iveef fects of light and UV exposure, thus increasing the service lif e of thematerial.

Light-resistanceThe abilit y of a plast ics material to resist fading af ter exposure to sunlight orult ra-violet light . Nearly all plast ics tend to darken under these condit ions.

Limiting Oxygen IndexThe concent rat ion of oxygen required to maintain burning. See ASTMProcedure D2863-74.

Linear Mold ShrinkageThe dif ference between the size of the part and the size of the mold cavit y.Values given are of ten the average of a range.

Linear MoleculeA long chain molecule as cont rasted to one having many side chains orbranches.

Linear Thermal ExpansionThe f ract ional change in length of a material for a unit change in temperature.

Liquid InjectionThe process that involves an integrated system for proport ioning, mixing, anddispensing two component liquid resin formulat ions and direct ly inject ing theresultant mix into a mold which is clamped under pressure.

Loss FactorThe product of the power factor and the dielect ric constant of a dielect ricmaterial.

Low Pressure LaminatesLaminates molded and cured in the range of pressures up to 400 psi

LubricantInternal lubricants, without af fect ing the fusion propert ies of a compound,promotes resin f low. External lubricants promote release f rom metals whichaids in the smooth f low of melt over die surfaces.

Luminescent PigmentsSpecial pigments available to produce st riking ef fects in the dark. Basicallythere are two types: one is act ivated by ult ra-violet radiat ion, producing veryst rong luminescence and, consequent ly, very eye-catching ef fects; the othertype, known as phosphorescent pigments, does not require any separatesource of radiat ion.

Luminous TransmittanceThe rat io of the luminous f lux t ransmit ted by a body of the f lux incident uponit .

Machine Shot CapacityRefers to the maximum weight of thermoplast ic resin which can be displacedor injected by the inject ion ram in a single st roke.

ManifoldA term used mainly with reference to blow molding and somet imes withinject ion molding equipment . It refers to the dist ribut ion or piping system whichtakes the single channel f low output of the ext ruder or inject ion cylinder anddivides it to feed several blow molding heads or inject ion nozzles.

MasterbatchA concent rat ion of a substance (an addit ive, pigment , f iller, etc.) in a basepolymer.

Mat1) A randomly dist ributed felt of f ibers, usually glass, used in reinforcedplast ics. 2) A nonwoven fabric of f ibrous material used as a plast icreinforcement .

Melamine PlasticsThermoset t ing plast ics made f rom melamine and formaldehyde resins.

Melt FlowRate of ext rusion of molten resin through a die of specif ied length anddiameter. The condit ions of the test (e.g. temperature and load) should begiven. Frequent ly, however, the manufacturer’s data list s only the value, not

the condit ion as well.

Melt FractureAn instabilit y in the melt f low through a die start ing at the ent ry to the die. Itleads to surface irregularit ies on the f inished art icle like a regular helix orirregularly-spaced ripples.

Melt IndexThe amount , in grams, of a thermoplast ic resin which can be forced through a0.0825 inch orif ice when subjected to 2160 grams. forced in 10 minutes at 190degrees C.

Melt StrengthThe st rength of the plast ic while in the molten state.

Melt TemperatureThe temperature of the molten plast ic just prior to entering the mold orext ruded through the die.

Melting PointThe temperature at which solid and liquid forms of a substance are inequilibrium. In common usage the melt ing point is taken as the temperature atwhich the liquid f irst forms in a small sample as it s temperature is increasedgradually.

MeniscusThe f ree surface of a liquid in a container, for example, water in contact withair conf ined in a capillary tube.

MerThe repeat ing st ructural unit in any high polymer.

Metalliz ingApplying a thin coat ing of metal to a non-metallic surface. May be done bychemical deposit ion or by exposing the surface to vaporized metal in avacuum chamber.

Metering ScrewAn ext rusion screw which has a shallow constant depth, and constant pit chsect ion over, usually, the last 3 to 4 f lights.

MicaA t ransparent , f laky mineral which split s into thin sheets and has excellentinsulat ing and heat resist ing propert ies, consist ing of orthosilicates ofaluminum or potassium; occurs naturally.

Modif iedContaining ingredients such as f illers, pigments or other addit ives that help tovary the physical propert ies of a plast ics material. An example is oil modif iedresin.

Modulus of ElasticityThe rat io of st ress to st rain in a material that is elast ically deformed.

Moisture ResistanceThe abilit y of a material to resist absorbing ambient moisture.

Moisture Vapor TransmissionThe rate at which water vapor permeates through a plast ic f ilm or wall at aspecif ied temperature and relat ive humidit y.

Mold(v.) To shape plast ic parts or f inished art icles by heat and pressure. (n.) (1)The cavit y or mat rix into which the plast ic composit ion is placed and f romwhich it takes it s form. (2) The assembly of all the parts that funct ioncollect ively in the molding process.

Mold Release AgentA lubricant used to coat a mold cavit y to prevent adhesion of the moldedpiece when removed.

MoldabilityThe characterist ics of being easy to mold without rupturing or developingf laws due o movement of the polymer during gelat ion.

Molding Cycle(1) The period of t ime occupied by the complete sequence of operat ions on amolding press requisite for the product ion of one set of moldings. (2) Theoperat ions necessary to produce a set of moldings without reference to thet ime taken.

Molding PressureThe pressure applied to the ram of an inject ion machine or press to force thesof tened plast ic completely to f ill t he mold cavit ies.

Molding ShrinkageThe dif ference in dimensions, expressed in inches per inch, between a moldingand the mold cavit y in which it was molded, both the mold and the moldingbeing at normal room temperature when measured.

Molecular Weight DistributionThe rat io of the weight average molecular weight to the number averagemolecular weight gives an indicat ion of the dist ribut ion.

MonomerThe simple, unpolymerized form of a compound which is the building block of apolymer.

Mounting PlateThe part of the blow molding unit to which the mold is at tached.

Movable PlatenThe large back platen of an inject ion molding machine to which the back halfof the mold is secured during operat ion. This platen is moved either by ahydraulic ram or a toggle mechanism.

Multi-cavity moldA mold with two or more mold impressions, i.e., a mold which produces morethan one molding per molding cycle.

Multiple Head MachineA (blow molding) machine in which the plast ic melt prepared by the ext ruder isdivided into a mult iplicit y of separate st reams (parisons) each givingult imately a f inished item.

NeckThe part of a container where the shoulder cross sect ion area decreases toform the f inish.

Neck BeadA prot ruding circle on a container at the point where the neck meets the f inish,the diameter of which usually equals the outside diameter of the closure.

Neck InsertPart of the mold assembly which forms the neck and f inish. Somet imes calledNeck Ring.

Nest PlateA retainer plate with a depressed area for cavit y blocks used in inject ionmolding.

NonpolarHaving no concent rat ions of elect rical charge on a molecular scale, thus,incapable of signif icant dielect ric loss. Examples among resins arepolystyrene and polyethylene.

Nonrigid PlasticA non-rigid plast ic is one which has a st if fness or apparent modulus ofelast icit y of not over 50,000 psi. at 25 degrees C when determined accordingto ASTM test procedure D747-43 T .

Notch SensitivityThe extent to which the sensit ivit y of a material to f racture is increased bythe presence of a surface in homogeneity such as a face notch, a suddenchange in sect ion, a crack, or a scratch. Low notch sensit ivit y is usuallyassociated with duct ile materials, and high notch sensit ivit y with brit t lematerials.

NozzleThe hollow cored metal nose screwed into the ext rusion end of (a) the heat ing

cylinder of an inject ion machine or (b) a t ransfer chamber where this is aseparate st ructure. A nozzle is designed to form under pressure a sealbetween the heat ing cylinder or the t ransfer chamber and the mold. The f rontend of a nozzle may be either f lat or spherical in shape.

NylonThe generic name for all synthet ic f iber-forming polyamides; they can beformed into monof ilaments and yarns characterized by great toughness,st rength and elast icit y, high melt point , and good resistance to water andchemicals. The material is widely used for brist les in indust rial and domest icbrushes, and for many text ile applicat ions; it is also used in inject ion moldinggears, bearings, combs, etc.

O-ringA ring used as a gasket .

Odorants & DeodorantsOdorants are used to add odor to materials, usually for safety reasons.

Of fsetA print ing technique in which ink is t ransferred f rom a bath onto the raisedsurface of the print ing plate by rollers. Subsequent ly, the print ing platest ransfer the ink to the object to be printed.

OhmPract ical unit of elect ric resistance.

Ohm’s LawThe st rength of a direct current is direct ly proport ional to the potent ialdif ference and inversely proport ional to the resistance of the circuit .

OpaqueDescript ive of a material or substance which will not t ransmit light . Oppositeof t ransparent . Materials which are neither opaque nor t ransparent aresomet imes described as semi-opaque, but are more properly classif ied ast ranslucent .

Orange FieldSaid of inject ion moldings that have unintent ionally rough surfaces.

OrientationThe alignment of the crystalline st ructure in polymeric materials so as toproduce a highly uniform st ructure. Can be accomplished by cold drawing orst retching during fabricat ion.

Orif iceThe opening in the ext ruder die formed by the orif ice bushing (ring) andmandrel.

Orif ice BushingThe outer part of the die in an ext ruder head.

OutgassingTo remove occluded gases by heat ing.

OvercoatingIn ext rusion coat ing, the pract ice of ext ruding a web beyond the edge of thesubst rate web.

OxidationThe addit ion of oxygen to a compound or the reduct ion of hydrogen.

Oxygen IndexSee Limit ing Oxygen Index.

Palletiz ingA process of producing pellets.

ParisonThe hollow plast ic tube f rom which a container, toy, etc. is blow molded.

Parison SwellIn blow molding the rat io of the cross-sect ional area of the parison to thecross-sect ional area of the die opening.

Parting AgentA lubricant , of ten wax, used to coat a mold cavit y to prevent the moldedpiece f rom st icking to it , and thus to facilit ate it s removal f rom the mold. Alsocalled Release Agent .

Parting LineMark on a molding or cast ing where halves of mold met in closing.

Partitioned Mold CoolingA large diameter hole drilled into the mold (usually the core) and part it ioned bya metal plate extending to near the bot tom end of the channel. Water isint roduced near the top of one side of the part it ion and removed on the otherside.

PelletA small ball or spherical shape.

Permanent SetThe increase in length, expressed in a percentage of the original length, bywhich an elast ic material fails to return to original length af ter being st ressedfor a standard period of t ime.

Permeability1) The passage or dif fusion (or rate of passage) of a gas, vapor, liquid or solid

through a barrier without physically or chemically af fect ing it . 2) The abilit y ofa material to carry magnet ism as compared to air which has a permeabilit y ofone.

PermittivityPreferred term for dielect ric constant . It is that property of a dielect ic materialthat determined how much elect rostat ic energy can be stored per unit ofvolume when unit voltage is applied; the relat ive permit t ivit y of most materialsvaries f rom 2 to 10, air having 1.

PHAn expression of the degree of acidit y or alkalinit y of a substance. Neut ralit yis pH -acid solut ions being under 7 and alkaline solut ion over 7. pH meters arecommercially available for accurate readings.

Phenolic Resin1) A synthet ic resin produced by the condensat ion of phenol with an aldehyde(usually formaldehyde). 2) Any of several t ypes of thermoset plast icsobtained by the condensat ion of phenol or subst ituted phenols.

PigmentAny colorant , usually an insoluble powdered substance used to produce adesired color of hue.

Pinpoint GateA rest ricted orif ice of 0.030 inches or less in diameter through which moltenresin f lows into a mold cavit y.

PitchThe distance f rom any point on the f light of a screw line to the correspondingpoint on an adjacent f light , measured parallel to the axis of the screw line orthreading.

Plastic1) High polymeric substances, including both natural and synthet ic products,but excluding the rubbers that are capable in their manufacture of f lowingunder heat and pressure. 2) A material that contains an organic substance oflarge molecular weight , solid in f inished state.

Plastic DeformationA change in dimensions of an object under load that is not recovered when theload is removed; opposed to elast ic deformat ion.

Plastic MemoryA phenomenon of plast ic to return to it s original molded form. Dif ferentplast ics possess varying degrees of this characterist ic.

PlasticityThe qualit y of being able to be shaped by plast ic f low.

PlasticizeTo sof ten a material and make it plast ic or moldable, either by means of aplast icizer or the applicat ion of heat .

PlasticizerAre usually low-melt ing solids or high-boiling organic liquids which, when addedto hard plast ics, impart f lexibilit y. They have varying degrees of sof teningact ion and solvat ing abilit y result ing f rom a reduct ion of intermolecular forcesin the polymer.

PlastisolMixtures of plast icizers and resins which can be converted to cont inuous f ilmsby applying heat .

Plate Dispersion PlugTwo perforated plates held together with a connect ing rod which are placed inthe nozzle of an inject ion molding machine to aid in dispersing a colorant in aresin as it f lows through the orif ices in the plates.

Plate-markAny imperfect ion in a pressed plast ic sheet result ing f rom the surface of thepressing plate.

PlatensThe mount ing plates of a press to which the ent ire mold assembly is bolted.

Platform BlowingA special technique for blowing large parts. To prevent excessive sag of theheavy parison the machine employs a table which af ter rising to meet theparison at the die descends with the parison but at a slight ly lower rate thanthe parison ext rusion speed.

Plug FormingA thermoforming process in which a plug or male mold is used to part iallypreform the part before forming is completed using vacuum or pressure.

Plug-and-ringMethod of sheet forming in which a plug, funct ioning as a male mold, is forcedinto a heated plast ic sheet held in place by a clamping ring.

PlungerSee Force Plug.

PneumaticMoved or worked by air pressure.

PoiseThe unit of viscosit y expressed as one dyne per second per squarecent imeter.

PolyamideA polymer in which the st ructural unit s are linked by amide or thioamidegroupings. Many polyamides are f iber-forming.

PolybutyleneA polymer prepared by the polymerizat ion of butene as the sole monomer.

PolyesterA resin formed by the react ion between a dibasic acid and a dihydroxyalcohol, both organic. Modif icat ion with mult i-funct ional acids and/or basesand some unsaturated reactants permit cross-linking to thermoset t ing resins.Polyesters modif ied with fat t y acids are called Alkyds.

PolyethyleneA thermoplast ic material composed by polymers of ethylene. It is normally at ranslucent , tough, waxy solid which is unaf fected by water and by a largerange of chemicals.

Polyimide ResinsA new group of resins recent ly int roduced in the United States. The material isan aromat ic polyimide made by react ing pyromellit ic dianhydride with aromat icdiamines. The polymer is characterized by the fact that it has rings of fourcarbon atoms t ight ly bound together, and the manufacturers claim that thenew resin has greater resistance to heat than any other unf illed organicmaterial yet discovered. Suggested applicat ions include components forinternal combust ion engines.

PolyisobutyleneThe polymerizat ion product of isobutylene. It varies in consistency f rom aviscous liquid to a rubber-like solid with corresponding variat ion in molecularweight f rom 1,000 to 400,000.

PolylinerA perforated longitudinally ribbed sleeve that f it s inside the cylinder of aninject ion molding machine; used as a replacement for convent ional inject ioncylinder torpedoes.

PolymerHigh-molecular-weight organic compound, natural or synthet ic, whosest ructure can be represented by a repeated small unit , the mer: e.g.polyethylene, rubber, cellulose. If two or more monomers are involved, acopolymer is obtained.

PolymerizationA chemical react ion in which the molecules of a monomer are linked togetherto form large molecules whose molecular weight is a mult iple of that of theoriginal substance. When two or more monomers are involved, the process iscalled copolymerizat ion or heteropolymerizat ion. See also Degree of ,Condensat ion, and Polymer.

Polymethyl MethacrylateA thermoplast ic material composed of polymers of methyl methacrylate. It isa t ransparent solid with except ional opt ical propert ies and good resistance towater. It is obtainable in the form of sheets, granules, solut ions, andemulsions. It is extensively used for aircraf t domes, light ing, f ixtures,decorat ive art icles, etc.; it is also used in opt ical inst ruments and surgicalappliances.

Polyolef inA polymer prepared by the polymerizat ion of an Olef in(s) as the soleMonomer(s).

PolyoxymethyleneA polymer in which the repeated st ructural unit in the chain is oxymethylene.

PolypropyleneA tough, lightweight rigid plast ic made by the polymerizat ion of high-purit ypropylene gas in the presence of an organometallic catalyst at relat ively lowpressures and temperatures.

Polystyrene .A water-white thermoplast ic produced by the polymerizat ion of styrene (vinylbenzene). The elect rical insulat ing propert ies of polystyrene are outstandinglygood and the material is relat ively unaf fected by moisture

Polytetraf luoroethylene (PTFE) ResinsMembers of the f luorocarbons family of plast ics made by the polymerizat ionof tet raf luoroethylene. PTFE is characterized by it s ext reme inertness tochemicals, very high thermal stabilit y and low f rict ional propert ies. Among theapplicat ions for these materials are bearings, fuel hoses, gaskets and tapes,and coat ings for metal and fabric.

Polyurethane ResinsA family of resins produced by react ing diisocyanate with organic compoundscontaining two or more act ive hydrogens to form polymers having f reeisocyanate groups. These groups, under the inf luence of heat or certaincatalysts, will react with each other, or with water, glycols, etc., to form athermoset t ing material.

Polyvinyl AcetalA member of the family of vinyl plast ics. Polyvinyl acetal is the general namefor resins produced f rom a condensat ion of polyvinyl alcohol with an aldehyde.There are three main groups: polyvinyl acetal it self ; polyvinyl butyl, andpolyvinyl formal. Polyvinyl acetal resins are thermoplast ics which can beprocessed by cast ing, ext ruding, molding and coat ing, but their main uses arein adhesives, lacquers, coat ings and f ilms.

Polyvinyl CarbazoleA thermoplast ic resin, brown in color, obtained by react ing acetylene with

carbazole. The resin has excellent elect rical propert ies and good heat andchemical resistance. It is used as an impregnate for paper capacitors.

Polyvinyl Chloride (PVC)A thermoplast ic material composed of polymers of vinyl chloride; a colorlesssolid with outstanding resistance to water, alcohols, and concent rated acidsand alkalies. It is obtainable in the form of granules, solut ions, lat t ices, andpastes. Compounded with plast icizers it yields a f lexible material superior torubber in ageing propert ies. It is widely used for cable and wire coverings, inchemical plants, and in the manufacture of protect ive garments.

Polyvinyl Chloride AcetateA thermoplast ic material composed of copolymers of vinyl chloride and vinylacetate; a colorless solid with good resistance to water, and concent ratedacids and alkalies. It is obtainable in the form of granules, solut ions, andemulsions. Compounded with plast icizers it yields a f lexible material superiorto rubber in aging propert ies. It is widely used for cable and wire coverings, inchemical plants, and in protect ive garments.

POMThe chemical abbreviat ion for Acetal, also known as Polyoxymethylene.

PostcureThose addit ional operat ions to which a cured thermoset t ing plast ic or rubbercomposit ion are subjected to enhance the level of one or more propert ies.

PostformingThe forming, bending, or shaping of fully cured, C-stage thermoset laminatesthat have been heated to make them f lexible. On cooling, the formedlaminate retains the contours and shape of the mold over which it has beenformed.

Powder MoldingGeneral term used to denote several techniques for producing objects ofvarying sizes and shapes by melt ing polyethylene powder, usually against theinside of a mold. The techniques vary as to whether the molds are stat ionary(e.g., as in variat ions on slush molding techniques) or rotat ing (e.g., as invariat ions on rotat ional molding).

Power FactorIn a perfect condenser, the current leads the voltage by 90 degrees. When aloss takes place in the insulat ion, the absorbed current , which produces heat ,throws the 90 degree relat ionship out according to the proport ion of currentabsorbed by the dielect ric. The power factor is the cosine of the anglebetween voltage applied and the current result ing.

Preform(n.) A compressed tablet or biscuit of plast ic composit ion used for ef f iciencyin handling and accuracy in weighing materials. (v.) To make plast ic molding

powder into pellets or tablets.

Preheat RollIn ext rusion coat ing, a heated roll installed between the pressure roll andunwind roll whose purpose is to heat the subst rate before it is coated.

PreheatingThe heat ing of a compound prior to molding or cast ing in order to facilit atethe operat ion or to reduce the molding cycle.

PreimpregnationThe pract ice of mixing resin and reinforcement before shipping it to themolder.

PrepregA term generally used in reinforced plast ics to mean the reinforcing materialcontaining or combined with the full complement of resin before molding.

Pressure FormingA thermoforming process wherein pressure is used to push the sheet to beformed against the mold surface as opposed to using a vacuum to suck thesheet against the mold.

Pressure PadsReinforcements or hardened steel dist ributed around the dead areas in thefaces of a mold to help the land absorb the f inal pressure of closing withoutcollapsing.

Pressure RollIn ext rusion coat ing, the roll which with the chill roll applies pressure to thesubst rate and the molten ext ruded web.

ProcessingAn average value is given rather than the temperature range of ten specif iedby the manufacturer.

Processing AidsSome processing aids include thixot ropic agents, f lat t ing agents, and blockingand ant icaking agents.

Processing MethodsThe kind of processing (ext ruding, molding, cast ing, etc.) techniquesrecommended by the manufacturer.

Prototype moldA simplif ied mold const ruct ion of ten made f rom a light metal cast ing alloy orf rom an epoxy resin in order to obtain informat ion for the f inal mold and/orpart design.

Pulp

A form of cellulose obtained f rom wood or other vegetable mat ter byprolonged cooking with chemicals.

Pulp moldingProcess by which a resin-impregnated pulp material is preformed byapplicat ion of a vacuum and subsequent ly oven cured or molded.

PurgingCleaning one color or t ype of material f rom the cylinder of an inject ion moldingmachine or ext ruder by forcing it out with the new color or material to be usedin subsequent product ion. Purging materials are also available.

Push UpThe bot tom contour of a plast ic container designed in such a manner as toallow an even bearing surface on the outside edge and to prevent the bot t lef rom rocking.

Radio Frequency WeldingA method of welding thermoplast ics using a radio f requency f ield to apply thenecessary heat . Also known as high f requency welding.

Ram TravelThe distance the inject ion ram moves in f illing the mold, in either inject ion ort ransfer molding.

RayonThe generic term for f ibers, staple, and cont inuous f ilament yarns composedof regenerated cellulose but also f requent ly used to describe f ibers obtainedf rom cellulose acetate or cellulose t riacetate. Rayon f ibers are similar inchemical st ructure to natural cellulose f ibers (e.g., cot ton) except that thesynthet ic f iber contains shorter polymer unit s. Most rayon is made by theviscose process.

Reaction InjectionA process that involves the high pressure impingement mixing of two or morereact ive liquid components and inject ing into a closed mold at low pressure.

Reciprocating ScrewAn ext ruder system in which the screw when rotat ing is pushed backwards bythe molten polymer which collects in f ront of the screw. When suf f icientmaterial has been collected, the screw moves forward and forces thematerial through the head and die at a high speed.

Recycled PlasticA plast ic prepared f rom used art icles which have been cleaned and reground.

Reformulated PlasticRecycled plast ic that has been upgraded to alter or improve performance

capabilit y or to change characterist ics through use of plast icizers, f illers,stabilizers, pigments, etc.

Ref ractive Index, Sodium DThe rat io of the velocit y and light in a vacuum to it s velocit y in the material.

RegrindWaste material f rom inject ion molding, blow molding and ext rusion operat ions,which has been reclaimed by shredding or granulat ing.

RegrindPlast ic that is re-int roduced into the product ion st ream.

Reinforced molding CompoundCompound supplied by raw material produced in the form of ready-to-usematerials; as dist inguished f rom premix.

Reinforced PlasticsA plast ic material with enhanced mechanical propert ies due to the addit ion ofhigh st rength f illers imbedded in the composit ion.

ReinforcementMaterial used to reinforce, st rengthen or give dimensional stabilit y to anothermaterial; can be chopped, woven or braided.

Relative HumidityRat io of the quant it y of water vapor present in the air to the quant it y whichwould saturate it at any given temperature.

Relative ViscosityThe relat ive viscosit y of a polymer in solut ion is the rat io of the absoluteviscosit ies of the solut ion (of stated concent rat ion) and of the pure solvent atthe same temperature.

Release AgentA lubricant , of ten wax, used to coat a mold cavit y to prevent the moldedpiece f rom st icking to it , and thus to facilit ate it s removal f rom the mold.

Relief AngleThe angle of the cutaway port ion of the pinch-of f blade measured f rom a lineparallel to the pinch-of f land.

Reprocessed PlasticA thermoplast ic prepared f rom scrap indust rial plast ic by other than theoriginal processor.

ResiliencyAbilit y to quickly regain an original shape af ter being st rained or distorted.

Resin

A pseudosolid or solid organic material of ten of high molecular weight . It has atendency to f low when subjected to st ress, usually has a sof tening or melt ingrange, and usually f ractured conchoidally.

Resin PocketAn apparent accumulat ion of excess resin in a small, localized sect ion visibleon cut edges of molded surfaces.

ResistanceProperty of a conductor that opposed the current f low produced by a givendif ference of potent ial. The ohm is the pract ical unit of resistance.

ResistivityThe abilit y of a material to resist passage of elect rical current either throughit s bulk or on a surface. The unit of volume resist ivit y is the ohm-cm., ofsurface resist ivit y, the ohm.

Restricted GateA very small orif ice between runner and cavit y in an inject ion or t ransfer mold.When the piece is ejected, this gate breaks cleanly, simplif ying separat ion ofrunner f rom piece.

Retainer PlateThe plate on which demountable pieces, such as mold cavit ies, ejector pins,guide pins, and bushings are mounted during molding; usually drilled for steamor water.

RheologyStudy of the deformat ion and f low of mat ter in terms of st ress, st rain andt ime.

RibA reinforcing member of a fabricated or molded part .

Rigid PlasticsFor purpose of general classif icat ion, a plast ic that has a modulus of elast icit yeither in f lexure or in tension greater than 100,000 psi at 23 degrees C and50% relat ive humidit y when tested in accordance with ASTM Methods D 747 orD 790 Test for st if fness of plast ics.

Rigid PVCPolyvinyl chloride or a polyvinyl chloride/acetate copolymer characterized by arelat ively high degree of hardness; it may be formulated with or without asmall percentage of plast icizer.

Rigid ResinHaving a modulus high enough to be of pract ical importance, e.g., 10,000 psi orgreater.

Rockwell Hardness

A test for hardness (resistance to indentat ion) in which a hardened steel ballor diamond point is pressed into the material under test .

RosinThe hard resin, amber to black in color, lef t af ter the dist illat ion of turpent ine.

Rotational moldingA method used to make hollow art icles f rom plast isols and lat t ices. Plast isol ischarged into a hollow mold capable of being rotated in one or two planes. Thehot mold fuses the plast isol into a gel af ter the rotat ion has caused it tocover all surfaces. The mold is then chilled and the product st ripped out .

Round SquarePart icular shape of a container which has sides of equal width with well-rounded corners and shoulders.

RubberAn elastomer capable of rapid elast ic recovery af ter being st retched to atleast twice it s length at temperatures f rom 0 to 150 degrees F, at anyhumidit y. Specif ically, heavy or natural rubber, the standard of comparison forelastomers.

RunnerIn an inject ion or t ransfer mold, the channel, usually circular, that connects thespruce with the gate to the cavit y.

ScarA characterist ic mark on plast ic containers which is conf ined most ly to thebot tom. It is caused by the pinch-of f operat ion and is of ten referred to as thelength of the pinch-of f .

ScrapAny product of a molding operat ion that is not part of the primary product . Incompression molding, this includes f lash, culls, runners, and is not reusable asa molding compound. Inject ion molding and ext rusion scrap (runners, rejectedparts, spruces, etc.) can usually be reground and remolded.

Sealing PlaneThe plane on the inside of a bot t le cap along the sealing surface.

Sealing SurfaceThe surface of the f inish of the container on which the closure forms the seal.

SeizingAct of holding or grasping suddenly or forcibly.

Self -extinguishingA somewhat loosely-used term describing the abilit y of a material to ceaseburning once the source of f lame has been removed.

Semipositive MoldA mold which allows a small amount of excess material to escape when it isclosed.

Semirigid PlasticFor purpose of general classif icat ion, a plast ic that has a modulus of elast icit yeither in f lexure or in tension of between 10,000 and 100,000 psi at 23 degreesC and 50% relat ive humidit y when tested in accordance with ASTM MethodD747 or D790 Test for St if fness of Plast ics.

Setting TemperatureThe temperature to which a liquid resin, an adhesive, or products orassemblies involving either is subjected to set the resin or adhesive.

Setting T imeThe period of t ime during which a molded or ext ruded product , an assembly,etc., is subjected to heat and/or pressure to set the resin or adhesive.

Shark SkinA surface irregularit y of a container in the form of f inely-spaced sharp ridgescaused by a relaxat ion ef fect of the melt at the die exit .

Shear RateThe overall velocit y over the cross sect ion of a channel with which moltenpolymer layers are gliding along each other or along the wall in laminar f low.

Shear Strength1) Abilit y of a material to withstand shear st ress or st ress at which a materialfails in shear. 2) The maximum shear st rength st ress that a material iscapable of sustaining.

Shear StressThe st ress developing in a polymer melt when the layers in a cross sect ion aregliding along the wall of the channel (in laminar f low).

SheetSheets are made of cont inuous phase plast ic in a form in which the thicknessis very small in proport ion to length and width. The thickness is greater than0.25 millimeters.

Sheet (thermoplastic)A f lat sect ion of a thermoplast ic resin with the length considerably greaterthan the width and 10 mils or greater in thickness.

Sheet TrainThe ent ire assembly necessary to produce sheet which includes ext ruder, die,polish rolls, conveyor, draw rolls, cut ter and stacker.

Shore HardnessA method of determining the hardness of a plast ic material using a

scelroscope. This device consists of a small conical hammer f it ted with adiamond point and act ing in a glass tube. The hammer is made to st rike thematerial under test and the degree of rebound is noted on a graduated scale.Generally, the harder the material the greater will be the rebound.

Short ShotIn inject ion molding, failure to f ill t he mold completely.

ShotThe yield f rom one complete molding cycle, including scrap.

Shot CapacityThe maximum weight of material which an accumulator can push out with oneforward st roke of the ram.

Shrink FixtureSee Cooling Fixture.

Shrink WrappingA technique of packaging in which the st rains in a plast ic f ilm are released byraising the temperature of the f ilm thus causing it to shrink over the package.These shrink characterist ics are built into the f ilm during it s manufacture byst retching it under cont rolled temperatures to produce orientat ion of themolecules. Upon cooling, the f ilm retains it s st retched condit ion, but revertstoward it s original dimensions when it is heated. Shrink f ilm gives goodprotect ion to the products packaged and has excellent clarit y.

ShrinkageCont ract ion of a container upon cooling.

SI UnitsThe Internat ional System of Unit s (Systems Internat ional) is a modernizedversion of the met ric system established by internat ional agreement . Itprovides a logical and interconnected f ramework for all measurements inscience, indust ry and commerce. Of f icially abbreviated SI, the system is builtupon a foundat ion of seven base unit s.

Side Draw PinsProject ions used to core a hole in a direct ion other than the line of closing of amold, and which must be withdrawn before the part is ejected f rom the mold.

SiliconeOne of the family of polymeric materials in which the recurring chemical groupcontains silicon and oxygen atoms as links in the main chain. At present thesecompounds are derived f rom silica (sand) and methyl chloride. The variousforms obtainable are characterized by their resistance to heat . Silicones areused in the following applicat ions: (a) Greases for lubricat ion. (b) Rubber-likesheet ing for gaskets, etc. (c) Heat stable f luids and compounds forwaterproof ing, insulat ing, etc. (d) Thermoset t ing insulat ing varnishes and

resins for both coat ing and laminat ing.

Silk Screen PrintingThis print ing method, in it s basic form, involves laying a pat tern of an insolublematerial, in out line, on a f inely woven fabric, so that when ink is drawn acrossit , it is able to pass through the screen only in the desired areas.

Single Cavity MoldAn inject ion mold having only one cavit y in the body of the mold, as opposedto a mult iple cavit y mold or family mold which have numerous cavit ies.

Sink MarkA shallow depression or dimple on the surface of an inject ion molded part dueto collapsing of the surface following local internal shrinkage af ter the gateseals. May also be an incipient short shot .

SinteringThe part ial welding together of powder part icles at temperature near themelt ing point .

SizingThe process of applying a material to a surface to f ill pores and thus reducethe absorpt ion of the subsequent ly applied adhesive or coat ing or tootherwise modify the surface. Also, the surface t reatment applied to glassf ibers used in reinforced plast ics. The material used is somet imes called Size.

SkinA relat ively dense layer at the surface of a cellular material.

Slip AdditiveA modif ier that acts as an internal lubricant which exudes to the surface ofthe plast ic during and immediately af ter processing. In other words, a non-visible coat ing blooms to the surface to provide the necessary lubricit y toreduce coef f icient of f rict ion and thereby improve slip characterist ics.

Slip AgentAn addit ive that provides surface lubricat ion during and immediately followingprocessing of the plast ic material. It acts as an internal lubricant which willeventually migrate to the surfaces.

Slip FormingSheet forming technique in which some of the plast ic sheet material is allowedto slip through the mechanically operated clamping rings during a st retch-forming operat ion.

Slip-planePlane within t ransparent material visible in ref lected light , due to poor weldingand shrinkage on cooling.

Slurry

A watery mixture of insoluble mat ter.

Snap-back FormingSheet forming technique in which an extended heated plast ic sheet is allowedto cont ract over a male form shaped to the desired contours.

SolventAny substance, usually a liquid which dissolves other substances.

Solvent MoldingProcess for forming thermoplast ic art icles by dipping a male mold in a solut ionor dispersion of the resin and drawing of f the solvent to leave a layer ofplast ic f ilm adhering to the mold.

Specif ic GravityThe densit y of any material divided by that of water at a standardtemperature.

Specif ic HeatThe amount of heat required to raise a specif ied mass by one unit of aspecif ied temperature.

Specular TransmittanceThe t ransmit tance value obtained when the measured t ransmit ted f luxincludes only that t ransmit ted in essent ially the same direct ion as the incidentf lux.

SpherulitesSpherical crystalline body of radiat ing crystal f ibers.

Spider(1) In a molding press, that part of an injector mechanism which operates theejector pins. (2) In ext rusion, a term used to denote the membranessupport ing a mandrel within the head/die assembly.

Spider LinesVert ical marks on the parison (container) caused by improper welding ofseveral melt f low f ronts formed by the legs with which the torpedo is f ixed inthe ext ruder head.

Spin WeldingA process of fusing two objects together by forcing them together while oneof the pair is spinning, unt il f rict ional heat melts the interface. Spinning is thenstopped and pressure held unt il t hey are f rozen together.

SpinneretA type of ext rusion die, i.e., a metal plate with many t iny holes, through whicha plast ic melt is forced to make f ine f ibers and f ilaments. Filaments may behardened by cooling in air, water, etc., or by chemical act ion.

SpinningProcess of making f ibers by forcing plast ic melt through a spinneret .

Spiral Flow TestA method for determining the f low propert ies of a thermoplast ic resin in whichthe resin f lows along the path of a spiral cavit y. The length of the materialwhich f lows into the cavit y and it s weight gives a relat ive indicat ion of the f lowpropert ies of the resin.

Spiral Mold CoolingA method of cooling inject ion molds or similar molds wherein the coolingmedium f lows through a spiral cavit y in the body of the mold. In inject ionmolds, the cooling medium is int roduced at the center of the spiral, near thespruce sect ion, as more heat is localized in this sect ion.

SplayA defect in the surface of a molded part that is usually small in size, shiny, andmay have the appearance of a light ly t inted or silver st reaks.

Split-Ring MoldA mold in which a split cavit y block is assembled in a chase to permit theforming of undercuts in a molded piece. These parts are ejected f rom themold and then separated f rom the piece.

Spray CoatingUsually accomplished on cont inuous webs by a set of reciprocat ing spraynozzles t raveling laterally across the web as it moves.

Spray-upCovers a number of techniques in which a spray gun is used as the processingtool. In reinforced plast ics, for example, f ibrous glass and resin can besimultaneously deposited in a mold. In essence, roving is fed through achopper and ejected into a resin st ream which is directed at the mold byeither of two spray systems. In foamed plast ics, very fast -react ing urethanefoams or epoxy foams are used in liquid st reams to the gun are sprayed onthe surface. On contact , the liquid starts to foam.

Sprayed Metal MoldsMold made by spraying molten metal onto a master unt il a shell ofpredetermined thickness is achieved. Shell is then removed and backed upwith plaster, cement , cast ing resin, or other suitable material. Used primarilyas a mold in sheet -forming processes.

SpreaderA st reamline metal block placed in the path of f low of the plast ic material inthe heat ing cylinder of ext ruders and inject ion molding machines to spread itinto thin layers, thus forcing it into int imate contact with the heat ing areas.

Spruce

The main feed channel that connects the mold-f illing orif ice with the runnersleading to each gravit y gate. Spruce is also the piece of plast ic materialformed in this channel.

Spruce BushingA hardened steel insert in an inject ion mold which contains the tapered sprucehole and has a suitable seat for the nozzle of the inject ion cylinder.Somet imes called an Adapter.

Spruce GateA passageway through which molten resin f lows f rom the nozzle to the moldcavit y.

Spruce LockIn inject ion molding, a port ion of the plast ic composit ion which is held in thecold slug well by an undercut ; used to pull the spruce out of the bushing as themold is opened. The spruce lock it self is pushed out of the mold by an ejectorpin. When the undercut occurs on the cavit y block retainer plate, this pin iscalled the Spruce Ejector Pin.

StabilizerAn ingredient used in the formulat ion of some plast ics, especially elastomers,to assist in maintaining the physical and chemical propert ies of thecompounded materials at their init ial values throughout the processing andservice lif e of the material.

Stabilizers & SurfaceSome addit ives included in this category include ant ioxidants and ant izonants,ant istats, biocides and fungicides, heat stabilizers, light , and UV stabilizersand absorbers.

StapleRefers to text ile f ibers of a short length, usually 1/2 to 3″, for natural f ibersand somet imes larger for synthet ics.

Stationary PlatenThe large f ront plate of an inject ion molding machine to which the f ront plateof the mold is secured during operat ion. This platen does not move duringnormal operat ions.

Straight-sided RoundA round bot t le with st raight side walls f rom shoulder to base.

Stress CrackA crack, either external or internal, in a plast ic caused by tensile st resses lessthan it s short -t ime mechanical st rength.

Stretch FormingA plast ic sheet forming technique in which the heated thermoplast ic sheet is

st retched over a mold and subsequent ly cooled.

StriationRippling of thick parisons, caused by a local orientat ion ef fect in the melt bythe spider legs.

Stripper-plateA plate that st rips a molded piece f rom core pins or force plugs. The st ripper-plate is set into operat ion by the opening of the mold.

Structural FoamThe process of molding thermoplast ics art icles with a cellular core andintegral solid skins in a single operat ion.

Submarine GateA type of edge gate where the opening f rom the runner into the mold islocated below the part ing line or mold surface as opposed to convent ionaledge gat ing where the opening is machined into the surface of the mold. Withsubmarine gates, the item is broken f rom the runner system in eject ion f romthe mold.

Surface ResistivityThe rat io of the potent ial gradient parallel to the current along it s surface tothe current per unit width of the surface.

Surface ResistivityThe elect rical resistance between opposite edges of a unit square ofinsulat ing material. It is commonly expressed in ohms. (Also covered in ASTMD257-54T .)

Surface TreatingAny method of t reat ing a polyolef in so as to alter the surface and render itrecept ive to inks, paints, lacquers, and adhesives such as chemical, f lame,and elect ronic t reat ing.

SurfactantA compound that af fects interfacial tensions between two liquids. It usuallyreduces surface tension.

SurfactantsThe use of these chemicals allows the format ion of an emulsion or int imatemixture of otherwise incompat ible substances by modifying the surfacepropert ies and inf luencing the wet t ing and f lowing propert ies of liquids.

SuspensionA mixture of f ine part icles of any solid with a liquid or gas. The part icles arecalled the disperse phase, the suspending medium is called the cont inuousphase.

Sweating

Exudat ion of small drops of liquid, usually a plast icizer or sof tener, on thesurface of a plast ic part .

SyndiotacticHaving a stereochemical regularit y where the molecules can be described interms of alternat ion of conf igurat ional base unit s that are mirror images ofone another.

SynergismA term used to describe the use of two or more stabilizers in an organicmaterial where the combinat ion of such stabilizers improves the stabilit y to agreater extent than could be expected f rom the addit ive ef fect of eachstabilizer.

Tab GatedA small removable tab of approximately the same thickness as the mold item,usually located perpendicular to the item. The tab is used as a site for edgegate locat ion, usually on items with large f lat areas.

TackSt ickiness of an adhesive, measurable as the force required to separate anadherent f rom it by viscous or plast ic f low of the adhesive.

Tackif iersAddit ives used to enhance the adhesiveness or bonding abilit y of a material.

Tapered CylinderRefers to a part icular shape of a container in which the circular cross sect ionat the top is smaller in diameter than that at the bot tom, or vice versa.

Tear Strength1) Force required to init iate or cont inue a tear in a material under specif iedcondit ions. 2) The force act ing substant ially parallel to the major axis of thetest specimen.

Tenacity (gpd)The term generally used in yarn manufacture and text ile engineering todenote the st rength of a yarn or of a f ilament for it s given size. Numerically itis the grams of breaking force per denier unit of yarn or f ilament size; gramsper denier, gpd. The yarn is usually pulled at the rate of 12 in./min. Tenacit yequals breaking st rength (grams) divided by denier.

Tensile Bar (specimen)A compression or inject ion molded specimen of specif ied dimensions which isused to determine the tensile propert ies of a material.

Tensile Modulus(Also called modulus of elast icit y). The rat io of nominal st ress to thecorresponding st rain below the proport ional limit of a material.

Tensile StrengthThe longitudinal st ress required to break a prescribed specimen divided bythe original cross-sect ional area at the point of rupture (usually expressed inlbs. Per square inch), within the gauge boundaries sustained by the specimenduring the test .

Tensile Strength, BreakThe maximum st ress that a material can withstand without breaking whensubjected to a st retching load.

Tensile Strength, YieldThe maximum st ress that a material can withstand without yielding whensubjected to a st retching load.

Thermal ConductivityThe rate of heat f low under steady state condit ions through unit area per unittemperature gradient in a direct ion perpendicular to an isothermal surface.

Thermal DegradationDeteriorat ion by heat .

Thermal Expansion Coef f icientThe f ract ional change in length (somet imes volume, specif ied) of a materialfor a unit change in temperature. Values for plast ics range f rom 0.01 to 0.2mils/in., degrees C.

Thermal Stress Cracking (TSC)Crazing and cracking of some thermoplast ic resins which result s f rom over-exposure to elevated temperatures.

ThermionicRelat ing to, using, or being the emission of charged part icles (as elect rons) byan incandescent material.

ThermoformingAny process of forming thermoplast ic sheet which consists of heat ing thesheet and pulling it down onto a mold surface.

ThermoplasticsResins capable of undergoing a chemical react ion leading to a relat iveinfusible and insolvable state.

ThermosetsResins or plast ic compounds, which in their f inal state are infusible andinsoluble. Af ter being fully cured, thermosets cannot be resof tened by heat .

Tie BarsBars which provide st ructural rigidit y to the clamping mechanism of ten used toguide platen movement .

ToleranceA specif ied allowance for deviat ions in weighing, measuring, etc., or fordeviat ions f rom the standard dimensions or weight .

Top BlowA specif ic t ype of blow molding machine forms hollow art icles by inject ing theblowing into the parison at the top of the mold

TorsionSt ress caused by twist ing a material.

TrackingA phenomenon wherein a high voltage source current creates a leakage orfault path across the surface of an insulat ing material by slowly but steadilyforming a carbonized path.

Transfer MoldingA process of forming art icles by fusing a plast ic material in a chamber thenforcing the whole mass into a hot mold to solidif y.

TranslucentDescript ive of a material or substance capable of t ransmit t ing some light , butnot clear enough to be seen through.

TransparentDescript ive of a material or substance capable of a high degree of lightt ransmission e.g., glass. Some polypropylene f ilms and acrylic moldings areoutstanding in this respect .

TumblingFinishing operat ion for small plast ic art icles by which gates, f lash, and f ins areremoved and/or surfaces are polished by rotat ing them in a barrel togetherwith wooden pegs, sawdust , and polishing compounds.

UL Temperature IndexThe maximum temperature below which a material maintains it s elect rical andmechanical integrit y over a reasonable period.

Ultimate StrengthTerm used to describe the maximum unit st ress a material will withstand whensubjected to an applied load in a compression, tension, or shear test .

Ultrasonic SealingA f ilm sealing method in which sealing is accomplished through the applicat ionof vibratory mechanical pressure at ult rasonic f requencies (20 to 40 KC.).Elect rical energy is converted to ult rasonic vibrat ions through the use of eithera magnetost rict ive or piezoelect ric t ransducer. The vibratory pressures at thef ilm interface in the sealing area develop localized heat losses which melt theplast ic surfaces ef fect ing the seal.

UltravioletZone of invisible radiat ion beyond the violet end of the spect rum of visibleradiat ion. Since UV wavelengths are shorter than the visible, their photonshave more energy, enough to init iate some chemical react ions and to degrademost plast ics.

Undercut(a.) Having a protuberance or indentat ion that impedes withdrawal f rom atwo-piece, rigid mold. Flexible materials can be ejected intact even with slightundercuts. (n.) Any such protuberance or indentat ion; depends also on designof mold.

Urea PlasticsPlast ics based on resins made by the condensat ion of urea and aldehydes.

UV StabilizerAny chemical compound which, when mixed with a thermoplast ic resin,select ively absorbs UV rays.

Vacuum FormingA process whereby a heated plast ic sheet is drawn against a mold surface byevacuat ing the air between it and the mold.

Vacuum MetallisingProcess in which surfaces are thinly coated with metal by exposing them tothe vapor of metal that has been evaporated under vacuum ( one millionth ofnormal atmospheric pressure).

Valley PrintingInk is applied to the high points of an embossing roll and subsequent lydeposited in what becomes the valleys of the embossed plast ic material.

VentIn a mold, a shallow channel or minute hole cut in the cavit y to allow air toescape as the material enters.

Vicat Sof tening PointThe temperature at which a f lat ended needle will penet rate a specimenunder a specif ic load using a uniform rate of temperature rise.

Virgin MaterialA plast ic material that has not been subjected to use or processing other thanthat required for it s init ial manufacture. It can be in the form of pellets,granules, powder, f loc, or liquid.

Virgin MaterialA plast ic material in the form of pellets, granules, powder, f lock, or liquid thathas not been subjected to use or processing other than that required for it sinit ial manufacture.

ViscosityInternal f rict ion or resistance to f low of a liquid. The constant rat io of shearingst ress to rate of shear. In liquids for which this rat io is a funct ion of st ress, theterm “apparent viscosit y” is def ined as the rat io.

Viscosity, InherentThe logarithmic viscosit y number determined by dividing the natural logarithmof the relat ive viscosit y (somet imes called viscosit y rat io) by theconcent rat ion in grams per 100 mls. of solut ion.

Viscosity, Relative (or Viscosity Ratio)Determined by dividing the average ef f lux t ime of the solut ion by the averageef f lux t ime of the pure solvent .

VoidAn unf illed space in a cellular plast ic which is substant ially larger than theindividual cells. Can also be an empty space in any material or medium.

VolatilesThat port ion of a substance that is readily vaporized.

Volume ResistivityThe measure of rat io of the potent ial gradient parallel to the current in thematerial to the current in densit y.

VulcanizationThe chemical react ion which induces extensive changes in the physicalpropert ies of a rubber and which is brought about by react ing the rubber withsulphur and/or other suitable agents. The changes in physical propert iesinclude decreased plast ic f low, reduced surface tackiness, increasedelast icit y, much greater tensile st rength, and considerably less solubilit y. Morerecent ly, certain thermoplast ics, e.g., polyethylene, have been formulated tobe vulcanisable. Cross-linking is encouraged, thereby giving resistance todeformat ion of f low above the melt ing point .

WarpageA nonuniform change in internal st resses result ing distort ion or warp of thematerial.

Water Absorption, 24 hoursThe percentage of water absorbed by a material when immersed in water for24 hours; water absorbed in a material chief ly af fects it s elect rical propert ies.

WeirA dam to divert water f low.

Weld LinesA mark on a container caused by incomplete fusion of two st reams of moltenpolymer. See Spider Lines.

Weld MarkA mark on a molded plast ic piece made by the meet ing of two f low f rontsduring the molding operat ion.

WeldingJoining thermoplast ic pieces by one of several heat -sof tening processes. Inhot -gas welding, the material is heated by a jet of hot air or inert gas directedf rom a welding “torch” onto the area of contact of the surfaces which arebeing welded. Welding operat ions to which this method is applied normallyrequire the use of a f iller rod. In Spin-Welding the heat is generated by f rict ion.Welding also includes heat sealing and the terms are synonymous in someforeign count ries including Britain.

Wet Lay-upA reinforced plast ic manufacturing process where the polymer compound isapplied as a liquid as the reinforcement is put into place.

Wet StrengthThe st rength of paper when saturated with water, especially used indiscussions of processes whereby the st rength of paper is increased by theaddit ion, in manufacture, of plast ic resins. Also, the st rength of an adhesivejoint determined immediately af ter removal f rom a liquid in which it has beenimmersed under specif ied condit ions of t ime, temperature, and pressure.

Wet WindingA f iber reinforcement material is coated with a polymer compound as a liquidprior to wrapping on a mandrel in the f ilament wound manufacturing process.

Wetting AgentWet t ing is produced when this surface act ive agent decreases the cohesionwithin a liquid. For wet t ing to occur, the adhesive force between the twophases (solid and liquid) is greater than the cohesive force within the liquid.

WhiskerA single-crystal, short f iber.

WrinkleAn imperfect ion in reinforced plast ics that has the appearance of a wavemolded into one or more plies of fabric or other reinforcing material.

Youngs Modulus of ElasticityThe modulus of elast icit y in tension. The rat io of st ress in a materialsubjected to deformat ion.

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