Delrin®

Acetal resins

Design with Delrin®

Start

with DuPont

Engineering Polymers

® D

uPon

t’s r

egis

tere

d tr

adem

ark

▲ ▲ ▲

Do You Speak Delrin®?▲▲

Introduction

Outstanding Attributes

List of Grades

Low Wear, Low Friction Series

Key Properties Table

Stiffness & Strength

Creep Resistance

Stress Relaxation

Fatigue Resistance

Impact Resistance

UV Resistance

Temperature

Chemical Resistance

Typical Applications

Radii

Uniform Wall Thickness

Ribs

Bosses

Threads

Snap Fits

Rapid Prototyping

Stockists/Machinists

Colours

Processing

Regrind & Recycling

Laser Marking

Medical Applications

Further Reading

Design Basics

Performance

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‘Design with Delrin®’Data at your fingertips

Delrin®

Acetal resins

Design

with

Delrin®

Start

with DuPont

Engineering Polymers

® D

uPon

t’s r

egis

tere

d tr

adem

ark

▲ ▲ ▲

Do You Speak Delrin®?

▲▲

Introduction

Outstanding Attributes

List of Grades

Low Wear, Low Friction Series

Key Properties TableStiffness & Strength

Creep Resistance

Stress Relaxation

Fatigue Resistance

Impact Resistance

UV Resistance

Temperature

Chemical Resistance

Typical ApplicationsRadii

Uniform Wall Thickness

Ribs

Bosses

Threads

Snap Fits

Rapid Prototyping

Stockists/Machinists

Colours

Processing

Regrind & Recycling

Laser Marking

Medical Applications

Further Reading

Samples

Design Basics

Performance

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& Strength

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This handbook makes basic information easily available todesigners and others and gives a quick reminder of theimpressive range of Delrin®

properties.

It is illustrated with a selectionof photographs showing someof the enormous variety ofapplications for which Delrin®

has already been successfullyused.

Use the colourcoded bars to helpyou ‘flick’ through tothe relevant sectionand data

‘Design with Delrin®’

Back to index

Delrin® versatility: snap fits to ski bindings, clips to conveyors,buckles to bicycle parts

Designers – use simple rules

to get the best from Delrin® in

“Design Basics”

View applications

throughout this binder

. . .Do you speak Delrin®? Are you as fluent as youwould like to be?

. . .Are you up to speed withall the new grades includingLow Wear, Low Friction, UVResistant and the ElevenSeries?

. . .Do you know whereDelrin® is used – and why?Have you heard of Delrin®

but don’t know what it feelslike?

. . .This Delrin® “phrase book”will help you brush up onyour acetal knowledge until itbecomes your first language.

Delrin® has a unique blend of

properties – understand them in

“Performance”

▲▲

Do You Speak Delrin®?▲

This publication is also available at http://www.dupont.com/enggpolymers/europe

4 5

Back to index

Delrin® versatility: skate parts, ski bindings, speaker grilles

What is Delrin®?Delrin® is an engineeringthermoplastic with a combination ofphysical properties not availableeither in metals or other plastics.

It has a well balanced profile ofmechanical properties, environmentalresistance and processability atmoderate cost.

Delrin® acetal resins providesubstantial strength, stiffness andcreep resistance.

Delrin® has gained widespreadrecognition for reliability ofperformance in many thousands ofengineering components all overthe world.

Since its commercial introduction byDuPont in 1960 it has been used in

the automotive, appliance,construction, hardware, electronicsand consumer goods industries.

I N T R O D U C T I O N

Delrin® acetal homopolymer was introduced by DuPont in 1960.Copolymer acetal followed somewhat later, around 1962.

Typical examples of Delrin® applications appear throughout this handbook

Trade name: Delrin®

Generic name: acetalSub class: homopolymer

Abbreviation: POM (polyoxymethylene)

Structure: highly crystalline polymerized formaldehyde

6 7

Back to index

Delrin® versatility: coloured lighters to carousels, pumps to pegs

O U T S TA N D I N G AT T R I B U T E S

This unique balance of properties makes Delrin® suitable for many metal replacement projects

The outstanding attributes of Delrin® acetal resins include:

Toughness at low temperatures(down to –40°C)

High mechanical strength and rigidity

Fatigue endurance unmatchedby other plastics

High resistance to repeatedimpacts

Excellent resistance tomoisture, petrol, solvents etc.

Excellent dimensional stability

Natural lubricity

Resilience

Good electrical insulatingcharacteristics

Ease of fabrication

Wide useful temperature range(in air –50 to +90°C withintermittent use up to 160°C

8 9

Back to index

Delrin®: whether standard or specialised, a grade forevery application

100 High viscosity100P High viscosity, easy processing.111P High viscosity, easy processing,

improved stability

500 Medium viscosity 500P Medium viscosity, easy processing511P Medium viscosity, easy

processing, improved stability

900P Low viscosity, easy processing911P Low viscosity, easy processing,

improved stability

1700P Very low viscosity, easyprocessing, improved stability

DE 9156 1,5% PTFE micropowder120MP 20% PTFE micropowderDE 9152 1,5% PTFE micropowder520MP 20% PTFE micropowder500AF 20% PTFE fibres500CL Chemical Lubricant500AL Advanced Lubricant900SP Special Polymer500SC Silicone Concentrate100KM Kevlar® Modified

LIST OF DELRIN® GRADES

Standard Low Wear/Low Friction

100ST Super tough, high viscosity100T Toughened, high viscosity500T Toughened, medium viscosity

Toughened

510GR 10%GR525GR 25%GR570 20%GF577 20%GF, UV resistant

Glass Reinforced/Filled

127UV High viscosity, best UV527UV Medium viscosity, best UV927UV Low viscosity, best UV1727UV Very low viscosity, best UV107 High viscosity, UV507 Medium viscosity, UV

Delrin® 100=high viscosity 500=medium viscosity 900=low viscosity

UV

1110

Back to index

Level 1Tribological system

Level 2 Requirements:

how can I avoid...?

Level 3Solution: appropriate

grade of Delrin®

High wear resistanceagainst aluminium

Delrin® 100KM ($$$)Delrin® 500CL ($$)Delrin® 500AL ($$)

($) . . . . ($$$$) = relative cost

L O W W E A R , L O W F R I C T I O N S E R I E S

The natural lubricity of Delrin® means it may be found unlubricated in many gear and bearing applications

Choosing Delrin® is a good starting point for applications inwhich wear and friction are majorissues. Unmodified Delrin® haslow friction and wear against steelas can be seen from the chartbelow.

THE FACTORS AFFECTINGWEAR AND FRICTION ARE:* Pressure of contact* Relative velocity* Temperature* Geometry of motion* Frequency of motion* Nature and finish of surface

* Lubrication

For metal as acounter surface,

the harder the surface the better the wear and

friction behaviour of the system.

Aim for a hardness of greater than

50 HRc

1000

100

10

1

0.00 0.10 0.20 0.30 0.40

P R O T O T Y P E T E S T I N G I S I M P O R T A N T

Spec

ific

wea

r ra

te(1

0-6 m

m3 /N

m)

Dynamic coefficient of friction, µ

Countersurface= steel PPO▲

ABS ▲

PBT▲ ▲ PA66

POM▲(Delrin®)

▲POM+20%PTFE(Delrin®)

New!

high PV

steel

Delrin®

againstmetal

low PV

Delrin® with low specific wear rate, ·ws

Delrin® 100/500/900 ($)Delrin® DE9156/DE9152 ($$)Delrin® 500CL ($$)Delrin® 500AL ($$)Delrin® 100KM ($$$)Delrin® 520MP ($$$)Delrin® 500AF ($$$$)

Wear

Best

Delrin® with low coefficient of friction, µ

Delrin® 100KM ($$$)Delrin® 100/500/900 ($)Delrin® DE9152/DE9156 ($$)Delrin® 500CL ($$)Delrin® 500MP ($$$)Delrin® 500AL ($$)Delrin® 500AF ($$$$)

Friction

Best

friction

wearaluminium

RESIN SELECTOR – DELRIN® AGAINST METAL

wear

Delrin® with low specific wear rate, ·ws

1312

Delrin® 100/500/900 ($)Delrin® 500CL ($$)Delrin® DE9152/DE9156 ($$)Delrin® 500AL ($$)Delrin® 100KM ($$$)Delrin® 520MP ($$$)Delrin® 500AF ($$$$)

Wear

Best

PV= pressure • velocity

Back to index

L O W W E A R , L O W F R I C T I O N S E R I E S

Please refer to the grades list for details of Low Wear, Low Friction Resins

When two parts are in contact in a wearsituation it is normal to choosedissimilar materials (eg Delrin® acetaland Zytel® nylon). Factors such asdimensional stability may make such achoice impossible, in which case thenew Low Wear, Low Friction gradesof Delrin® may be suitable. The tablebelow shows the improvement inwear and friction compared tostandard grades.

0.10 0.20 0.30 0.40

Spec

ific

wea

r ra

te(1

0-6 m

m3 /N

m)

New Grades

●900SP

StandardGrades

100P●

10000

100

1000

10

1

Countersurface

= Delrin®

Quieter too!Certain grades reduce noise(squeak) dramatically comparedwith standard grades

. . . continuedLevel 1Tribological

system

Level 2 How can I

avoid...?

Level 4 Solution: otherthan material

choice

Level 3Solution: appropriate

grade of Delrin®

($) . . . . ($$$$) = relative cost

15

friction

impactnoise orfailure

wear

squeak

Non-squeaking grades of Delrin®

Delrin® toughened grades(external lubrication needed)

Delrin®

againstDelrin®

Delrin® 500SC@10% ($)Delrin® 500AL ($$)Delrin® 900SP ($$)Delrin® 120MP/520MP ($$$)Delrin® 500AF ($$$$)

Delrin® with low specific wear rate, ·ws

Delrin® DE9156/DE9152 ($$)Delrin® 500SC @ 5% ($)Delrin® 500AF ($$$$)Delrin® 500AL ($$)Delrin® 900SP ($$)Delrin® 500SC @ 10% ($)Delrin® 120MP/520MP ($$$)

Delrin® with low coefficient of friction, µ

Delrin® DE9156/DE9152 ($$)Delrin® 500AF ($$$$Delrin® 520MP ($$$)Delrin® 120MP ($$$)Delrin® 500AL ($$)Delrin® 500SC @ 5% ($)Delrin® 900SP ($$)Delrin® 500SC @ 10% ($)

Friction

Best

Delrin® 100T ($)Delrin® 500T ($)Delrin® 100ST ($$)

Wear

Best

external lubrication

other material forcounter surface

external lubrication

external lubrication

optimise design

reduce pressure

14

RESIN SELECTOR – DELRIN® AGAINST DELRIN®

●500AL

DE 9152●

●520MP

Dynamic coefficient of friction, µ

Back to index

K E Y P R O P E R T I E S TA B L E

Delrin® 100 is the toughest unmodified acetal available with a unique combination of elongation and stiffness

Based on Delrin® 100 high viscosity acetal

Yield stress

Yield strain

Strain at break

Flexural modulus

Izod notched impactstrength @ 23°C

@–40°C

Temperature of

deflection under load

Melt temperature

Flammability

Shrinkage

Melt Flow Index

Chemical Resistance

Density

71

25

70

2800

128

115

177

HB

1,9 to 2,2

2,2

outstanding

1,42

MPa

%

%

MPa

kJ/m2

°C

°C

%

g/10 min

g/cm3

Property Units Value

For graphssee next section

Campusdiskette

available

Delrin®: stiff, strong, tough, chemically resistant

16 17

Back to index

The exceptional elongation coupled with stiffness makes Delrin® suitable for snap fits

To judge the stiffness and springiness of Delrin® ask your nearest DuPont Engineering Polymers office for test bar samples.

The modulus of Delrin® isaffected by changes in thetemperature as shownbelow.

3

2

Temperature (°C)

Youn

g’s

mod

ulus

(G

Pa)

1

0 —20 0 20 40 60 80 100

The mechanical response to short term loads

is shown above

Strain (%)

Str

ess

(MPa

)

20

0 0 2 4 6 8 10

40

60

80

-20°C 23°C

90°C

Material chosen and whyDelrin® 100 was chosen for its unique balance of stiffness and strength

Description/ApplicationSnap fit buckle

18 19

P E R F O R M A N C E

Stiffness and Strength

Young’s modulus of Delrin®

as a function of temperature

Stress v Strain at –20°C,23°C and 90°C

Back to index

P E R F O R M A N C E

Upon removal of a 14 MPa deforming stress, Delrin® immediately recovers 40% of the imposed strain

Creep is defined as time dependentstrain, resulting from stress.

Str

ess

(M

Pa)

20

15

10

5

00 0,5 1,0 1,5 2,0 2,5

I s o c h r o n o u s s t r e s s / s t r a i nD e l r i n® 1 0 0 @ 2 3 ° C

1h10

h10

0 h

1000

h50

00 h

1000

0 h

Total strain (%)

Creep

Always try to design partsso that they arenot permanentlyloaded

The factors affecting creep are:*Stress level*Time*Temperature

Material chosen and whyDelrin® 100 was chosen for its good spring characteristics and superior creep

compared with polyamide, polypropylene and acetal copolymer

Description/ApplicationClothes peg

20 21

100

000

h

(proje

cted) Delrin® Acetal Resins

have extremely goodcreep resistance for anunreinforced polymer

Back to index

P E R F O R M A N C E

Stress free mouldings may be obtained by annealing Delrin®

at 160°C for 45 mins

Stress relaxation is defined asdecrease of the stress required to

maintain constant strain.

% o

f in

itia

l st

ress

100

80

40

20

10

0,01 0,1 1,0 10 100 1000 10000

Te n s i l e s t r e s s r e l a x a t i o n o fD e l r i n®1 0 0 a n d 5 0 0 @ 2 3 ° C

Hours

Stress relaxation

Strain 0,3%. 17 MPa0,9%. 34 MPa

5%. 66 MPa

12,5%.Yield point strain 69 MPa

Stress relaxation is particularlyimportant whenconsidering press-fit assembly

Material chosen and whyDelrin® 100P was chosen for its good friction properties and a balance of

impact and creep resistance with high dimensional stability

Description/ApplicationCar window guides

22 23

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P E R F O R M A N C E

Delrin® Acetal Resins have extremely high resistance to fatigue failure from –40°C to +80°C

Fatigue

When materials are stressed cyclically at high levels of stress in relation to their tensile strength,they tend to fail at levels of stressbelow their ultimate tensilestrength.

This phenomenon is termed “fatigue failure.”

Str

ess

(M

Pa)

50

40

30

20

10

0103 104 105 106 107

C y c l e s t o f a i l u r e

Fatigue failure stress of Delrin®compared withother plastics106 cycles, 23°CMaterial Stress

(MPa)Polycarbonate 10ABS 11Polypropylene 15Delrin® acetal 32

Material chosen and whyDelrin® 100 was chosen for the best balance of stiffness and strength coupledwith flex fatigue resistance needed for the spring fingers of the tool gripper

Description/ApplicationTool changer carousel

24 25

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P E R F O R M A N C E

Delrin® acetal maintains its high toughness down to very low temperatures

Impact resistance is definedas the ability to withstand asudden blow rather than aslowly applied load.

Impact Resistance

60

Charpy Impact Strength (23°C)

Impa

ct s

tren

gth,

kJ/m

2

500 500T 100 100T 100ST

50

40

30

20

10

0

20

15

10

Temperature, °C

Impa

ct s

tren

gth,

kJ/m

2

5

0

R

-40 -20 0 20 40 60

Izod Impact v Temp Delrin 100

See also Effect of Radii in‘Design Basics’

▲

Description/ApplicationRollerblade brake

Material chosen and whyDelrin® 100ST was chosen for the best combination of stiffness and

impact resistance at low temperature, combined with good mouldability

2726

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P E R F O R M A N C E

The Delrin® UV family of resins are well suited for sporting goods and otheritems which are used outdoors but stored indoors

Acetal resins, like mostpolymers, are affected bylight, particularly sunlightwhich includes ultra-violetradiation of wavelength290-400 nm.

UV Resistance

R

Exposure, kJ/m2

Rel

ativ

eG

loss

0

1,0

0,5

500 1000

x27UV BK

x07 BKx00 BK

Exposure, kJ/m2

Rel

ativ

eTe

nsile

Stre

ngth

0

0,5

500 1000

UV Stabilised

Standard

1,0

Accelarated Interior Weatheringaccording to SAE J-1885

Coloured Delrin® resinsoffer some UVprotection. High levelsof carbon black act asan effective UV screenfor non-critical outdoorapplications

Typical values for Delrin® grade 527UV compared with other grades.

Material chosen and whyDelrin® 127UV was chosen for its excellent balance of mechanical

properties combined with good UV resistance

Description/ApplicationMoped brake lever

29

Colours

▲

28

Back to index

P E R F O R M A N C E

The thermal stability ofDelrin® means it finds use in applications from –50°C to +90°C

The highly crystallinenature of Delrin® means it is suitable for short-termexposure to temperaturesclose to the melting pointof 177°C.

Temperature

Specific HeatThermal Conductivity(W/m • K)

Key ThermalCharacteristicsProperty

Melt temperatureVicat Softening10 N50 NRelative ThermalIndex (w/o impact)HDT (1,8 MPa)Ball Pressure Test

°C

177

174160

90115165

1 2 5 10

100

75

50

Exposure time in years for which tensile strength in excess of 55 MPa is retained

Air

Tem

pera

ture

(0 C

)

If you need higher temperature resistance,consider DuPont Zytel® nylons , Crastin® and Rynite®

polyesters or Zenite™ LCPs.

Material chosen and whyDelrin® 100 was chosen for its good thermal stability combinedwith a low coefficient of friction and superior impact resistance

Description/ApplicationBearing roll cages

30 31

After 1 yearat 100°CDelrin® retains80% of itstensile strength

0,35

0,30to0,37

Back to index

Delrin® has excellent resistance to moisture, gasoline, lubricants, solvents and many neutral chemicals

Do not use Delrin®

in strong acids or

bases outside the

range of pH 4 to 9

CHEMICAL BEHAVIOUR

Acetic acid (5%) resistantAcetic acid (50%) unsatisfactoryAcetone resistantAir (all pressures) resistantAlcohol (all types) resistantAmmonia (10%) unsatisfactoryAniline limited resistanceBenzene resistantBleaching fluid (10% chlorine) unsatisfactoryBrake fluid resistantButane resistantCalcium chloride (10%) resistantCarbon dioxide resistantCarbon monoxide resistantChloracetic acid (10%) unsatisfactoryChlorine gas unsatisfactoryChlorinated water < 0,5 ppm resistantChloroform limited resistanceChromic acid (10%) unsatisfactoryCitric acid resistantCyclohexane resistantDetergents resistantDiesel fuel resistantEthanol resistantEthyl acetate resistant

P E R F O R M A N C E

Chemical Resistance

The factors affecting

chemical resistance are:

* Concentration

* Time

* Temperature

* Stress Level

14 Alkali

9

7 Neutral

4

0 Acid

Description/ApplicationPool cleaner swivel bearing

Material chosen and whyDelrin® 500P was chosen for its excellent wear properties, chemical

resistance, snap-fit ability and dimensional stability

32 33

Back to index

P E R F O R M A N C E

CHEMICAL BEHAVIOUR

Ethyl ether resistant

Ethylene glycol resistant

Formaldehyde (37%) resistant

Formic acid unsatisfactory

Fuel oil resistant

Gasoline resistant

Glucose (sat.sol.) resistant

Heptane resistant

Hexane resistant

Hydrochloric acid (10%) unsatisfactory

Hydrofluoric acid unsatisfactory

Hydrogen peroxide (1%) resistant

Hydrogen peroxide (30%) unsatisfactory

Hydrogen sulphide unsatisfactory

Insecticides resistant

Isoctane resistant

Jet fuel /kerosene resistant

Lubricating oil resistant

Methyl chloride limited resistance

Methylene chloride limited resistance

Methyl ethyl ketone limited resistance

Mineral oil resistant

Motor oil resistant

Nitric acid (10%) unsatisfactory

CHEMICAL BEHAVIOUR

Nitrous acid unsatisfactory

Nitrous oxide (dry) unsatisfactory

Oils (food) resistant

Oils (mineral) resistant

Oleic acid resistant

Palmitic acid resistant

Paraffins resistant

Perchloric acid (10%) unsatisfactory

Phosphoric acid (30%) unsatisfactory

Phthalic acid resistant

Potassium hydroxide (10%) unsatisfactory

Propane (liquified gas) resistant

Sodium chloride (10%) resistant

Sodium hydroxide (10%) unsatisfactory

Sodium hypochlorite (5%) unsatisfactory

Sulfur dioxide unsatisfactory

Sulphuric acid (30%) unsatisfactory

Tetrahydrofuran resistant

Toluene resistant

Trichloroacetic acid unsatisfactory

Trichloroethane (1,1,1) resistant

Turpentine / white spirit resistant

Urea (5%) resistant

Vinegar resistant

Chemical Resistance cont.

Material chosen and whyDelrin® 500P was chosen for its good petrol resistance,

good mechanical properties and ease of moulding

Description/ApplicationFuel level device

34 35

Back to index

T Y P I C A L A P P L I C AT I O N S

The exceptional balance of properties has led to a diverse use ofDelrin® around the world

Ski Bindings

Clips Door Handles Fuel Systems

Zips Conveyors

Fasteners Speaker Grilles

Lighters Gears

Toughness @–40°CUV performance

Strength,stiffness, lowwear, low friction

Low friction, brightcolours

Elongation, fatiguestrength

Stiffness, low friction,UV performance

Chemical resistance

Economical, toughness Easy flow, impact performance

Low wear, quietoperation

Chemical resistancePressure vessel

Do it in Delrin®. . .

. . . nothing does it better

36 37

Back to index

D E S I G N B A S I C S

Delrin® like many plastics, is notch-sensitive but unlike other resinsit has high impact strength at low temperatures

Str

ess

Fac

tor

R/T

Radii use of radii has three main functions* Reduces notch effect * Helps material flow* Eases ejection frommould

see also

ImpactPerformace

▲

Always use radii

at rib junctions

and stressed areas

but also consider

thread terminations,

knurled inserts and

surface textures

Material chosen/Design commentDelrin® 111P was chosen for this application. Radii lowers stress

concentration when parts are put under load

Description/ApplicationSpring clips

38 39

0 0,2 0,4 0,6 0,8 1,0 1,2 1,41,0

1,5

2,0

2,0

Usual

P = Applied LoadR = Fillet RadiusT = Thickness

P

T

R3,0

Back to index

Even wall section will greatly benefit highly crystallinepolymers such as Delrin®

Even wall thickness

gives:

* Even shrinkage

– less distortion

* Even set-up

– quickest moulding

cycle

* Less material

– low cost

Choosing the correct wallthickness for a moulded partis a function of end useconstraints (what does thepart have to do?), moulding factors, (what is the thinnestsection that can be moulded?)and overall cost.

The exact thickness may beestimated by the use of FiniteElement Analysis (FEA) usedin both part design and flowanalysis, but where possibleshould be relatively constant throughout.

D E S I G N B A S I C S

Uniform Wall Thicknesses

Description/ApplicationRatchet mechanism

Material chosen/Design commentDelrin® 500P. Low distortion and cost efective part ensured

by use of even wall thickness

40 41

Back to index

If ribbing is unacceptable, Delrin® 510GR and 525GRoffer significant increase in stiffness

Ribs are an effective way

to improve the rigidity of

moulded parts.

For Delrin®, ribs should be

1/2 to 2 /3 the general wall

thickness, with 1/4° to

1/2°draft angle per side.

Sink marks caused byribs may be hidden

by use of textured surface orsuitable interruption in thearea of the sink.

D E S I G N B A S I C S

Ribs

Proper use of ribs will:

* Save material and weight

* Shorten moulding cycle

* Eliminate voids in thicksections

Description/ApplicationCross beam

Material chosen/Design commentDelrin® 100P enables increased stiffness to be achieved by

use of ribs without compromising surface finish

42 43

Back to index

Weld lines should be avoided in bosses. Delrin® being generallyunreinforced, has excellent weld line strength

D E S I G N B A S I C S

Bosses are used for

mounting purposes or for

reinforcement around holes.

As a rule the outside

diameter of a boss should be

2 to 3 times the hole

diameter.

Heavy sections may be

avoided by stepping the boss

off the adjoining wall.

Use radii at all junctions.

Always use screws designed forplastics when consideringassembly. These may be singleor twin-start threaded ortrilobular screws. Repeatedassembly and disassembly ispossible with Delrin®.

Bosses

Boss Design

***

Hole dia = 0,75 x nominaldia of screw

Boss dia : 2 to 3 times hole dia

Hole depth 2 x nominalscrew dia minimum

Description/ApplicationFuel flange

Material chosen/Design commentDelrin® 511P. Boss and linking rib design

provides accurate hole centres

4544

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D E S I G N B A S I C S

When required, threads maybe automatically mouldedinto the part, eliminating theneed for mechanical thread-forming operations.For external threads, it maybe possible to locate theparting line on the centre ofthe thread.For internal threads, anautomatic unscrewing deviceis used in the tool.

To avoid ‘squeak’ on heavilyloaded threads, consider theLow Wear, Low Friction gradesof Delrin®

Use of a buttress

type thread will

avoid unnecessary

radial forces on

the mating part

Correct termination of threads

▲

The dimensional stability ofDelrin® makes it very suitable for the moulding of accurate thread forms

Threads

Description/ApplicationIndustrial valve

Material chosen/Design commentDelrin® 500P. Moulded thread form avoids machining

4746

1mm

Round threads

Back to index

The combination of stiffness and elongation makesDelrin® very suitable for snap fits

L

R

D E S I G N B A S I C S

Snap Fits are a cost effectiveway of assembling partstogether without the use ofspecial tools.

Usually the parts are at restbefore and after assemblyand pass through a stressedcondition as the snap fit ismade to work.

With Delrin®, a single use snapfit may be stressed up to 8%strain (Delrin® 100). For afrequently used one refer tothe fatigue stress graph

Snap Fits

Delrin® is also excellent forcircular and spherical snapfit designs

Cantilever Snap Fits

***

Make ‘L’ as long

as possible

Taper snap fit lug

Use radii at root

▲

Description/ApplicationCable guide

Material chosen/Design commentSnap fit in Delrin® 500 gives strong, rattle-free connection

48 49

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Prototyping tipsKeep heat generatedduring machining to aminimum

Support thin wallsand long partsBe aware of the notcheffect of machiningparts

R A P I D P R O T O T Y P I N G

Delrin® has excellent machining characteristics using conventional tools

In order to test parts in the actualmaterial it is normally necessaryto mould them. Due to the easeof machining of Delrin®, it maybe possible to prototype partsby NC machining, utilising theCAD data which describesthe part geometry.

ModifyGeometry

Mould Parts

7

5a

*

*

*

Delrin®

stockists/machinists

▲Shoehorn prototype

CNC machining of simple shapes possible in Delrin®

50 51

CAD Data

1

Test Parts

5

NC MachineMould Tool

6

Hand Finish

4

Create Tool

Paths

Machine Stock Shapes(Block, Rod)

32

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S T O C K I S T S / M A C H I N I S T S

Details of companies experienced in machining Delrin® acetal resinsare also available from your DuPont representative

Contact your DuPont representative for detailedinformation on your local Delrin® stockist

Rod stock, slab

Always ask for Delrin® by name

52 53

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C O L O U R S

No heavy metals are used in Delrin® Colours

Typical referencecodes for

Delrin® colours

I d e a l l y a n y m a s t e r b a t c h s h o u l d b e a c e t a l b a s e d

NC = Natural

BK = Black

WT = White

GY = Grey

GN = Green

BL = Blue

YL = Yellow

RD = Red

Pigmentsmay affectshrinkage –test first!

Custom colours areavailable as fully

compounded productfrom DuPont or bymasterbatch from pigment suppliers

S h r i n k a g e v. C o l o u r

NC

WT

YL

BK

BL

GY

RD

GNCOLOUR

SHR

INK

AG

E(%

)

2,1

2,0

1,9

1,8

Delrin® The heart of a good product

54 55

1,7

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For specific processing information ask for the free booklet‘Delrin® Moulding Manual’

The most important variablesin producing good parts by

injection moulding are:

Above all, a good qualityhomogeneous melt is required.

* Melt temperature

* Injection speed

* Hold pressure

* Screw forward time

* Mould temperature

Always dry toughened gradesfor 4 hours at 80°C

P R O C E S S I N G

Melt Temp(°C)

215 90 100 8 30 1,9 - 2,2

MouldTemp(°C)

HoldPressure

(MPa)Hold PressureTime (s/mm)

Max Hold Up Time

(min)Shrinkage

(%)

Typical set-up conditions forDelrin® 100 are shown below.

Material chosen and whyDelrin® 927UV was chosen for its excellent mouldability and impact resistance.

Its resistance to UV and easy colourability are additional assets

Description/ApplicationVenting system grille

5756

Grades based on the ‘P’ stabilisation system are suitablefor hot runner tools,these include

100P, 500P, 900P,1700P127UV, 527UV, 927UV,1727UV,111P, 511P, 911P.

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R E G R I N D & R E C Y C L I N G

It is important to use analytical techniques in part design to reduce the impact of recyclate on the environment

RECYCLING

The combination of

stiffness and elongation

that makes Delrin® so

effective in snap fits also

means that parts may be

disassembled prior

to recycling.

The long term stability

of Delrin® means that

parts may be reground

and remoulded with

little effect on

properties.

Incineration is an energy

efficient alternative

>POM<

Description/ApplicationGolf tee

Material chosen and whyDelrin®100 regrind was chosen for the shank. Capable ofwithstanding high impact, it provides the correct rigidity

5958

REGRIND

Up to 25% of properlyground sprues and runners may be mixedwith virgin resin with little or no effect onmechanical properties.Toughened grades willneed to be dried priorto moulding.For glass reinforcedgrades, use a slow speedon the grinder rotor.

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L A S E R M A R K I N G

See also Delrin® colours

Laser marking is particularly suitable when

the batch sizes are small and marking variability is required

(e.g. serial numbers or different languages).

. . .BK-L01 Black

. . .BL-L01 Blue

. . .BN-L01 Brown

. . .GN-L01 Green

. . .GY-L01 Grey

. . .RD-L01 Red

. . .WT-L01 White

Advantages* High rate contactlessprocess

* Flexibility, easy changeof layout and charactertype

* No surface pre-treatment,no solvent, no ink* High durability of themarking

A range of colours specially optimised for laser marking is available in Delrin®.Tested with severalNd:YAG lasersystems, thesecolours provide highcontrast markingswith almost noengraving

LASER = Light Amplification by

Stimulated Emission of Radiation

Colours for laser marking 500LM ...

▲Material chosen and whyDelrin® 500LM BK-L01 was chosen for its clarity of laser marking

plus its mechanical properties

Description/ApplicationSki adjuster

6160

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M E D I C A L A P P L I C AT I O N S

Delrin® acetal resin is notcertified for implants

Do not use DuPont materials in medicalapplications involving

permanent implantation in thehuman body or permanentcontact with internal body

fluids or tissue.

Do not use DuPont materials in medical

applications involving brief ortemporary implantation in thehuman body or contact withbody fluids or tissues unless

the material has been provideddirectly from DuPont under a

contract which expresslyacknowledges the

contemplated uses.

For food contact or pharmaceutical

applications, regulatorycompliance statements are

available, please contact your local DuPont

representative fordetails.

DuPont makes norepresentation, promise,express warranty or impliedwarranty concerning thesuitability of these materialsfor implantation in the humanbody or in contact withinternal body fluids or tissues.

✠CAUTION

✚

Description/ApplicationMedical tube clip

Material chosen and whyDelrin® 500P was chosen for its chemical resistance and springiness

6362

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F U R T H E R R E A D I N G

The general brochure covering all DuPont engineering polymersis called ‘From concept to commercialisation’

To access furtherinformation concerningany topic covered in this

binder, please contactyour local DuPont office

Access information onDelrin® at our internet

address:http://www.dupont.com/

enggpolymers/europe

Delrin® Product guide and properties

DesignInformation

MouldingManual

Main Literature for Delrin®

▲▲

▲

▲

DuPont has a wide

selection of literature

covering specific

application areas

such as Appliances,

Automotive, Electrical,

Furniture etc.,

together with a

General Design Principles

handbook which covers all

DuPont engineering resins

Technical Information

A wealth of experience available in various formats64 65

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Delrin®. Chosen for reliability of performance in many thousands of engineering components all over the world

Delrin® Makes the Difference

66

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