industrial manufacturing of nitrile rubber

8/14/2019 Industrial manufacturing of Nitrile Rubber

1/32

Industrial manufacturing of Nitrile Rubber

INTRODUCTION

Acrylonitrile Butadiene copolymers are commonly known as

Nitrile rubbers. India has consuming this rubber for over four decades,

however, the consumption remained small and restricted to mainly the

products requiring oil resistance properties. The picture changed rapidly since

1970 as the combined properties of abrasion resistance even at high

temperatures was used for making products like rice dehusking rolls. Today

over 2500 MT of NBR is used in this single application the growth of

automotive industries, oil companies have further spurred the demand of

Nitrile rubbers in India.

The first rubber is to be commercialized is Natural rubber. Since

that time two attempts have been made by scientists world over to study the

structure of natural rubber, elasticity of natural rubber and then try to synthesis

a rubber that can do the job of natural rubber. During the World War II(1941),

these attempts got the boost, when allies realized that natural rubber comes

from East Asia was under the threat of Japanese aggressiveness and that wars

cannot be fought without rubber i.e. rubber tyres etc. Synthetic rubber

manufacturing programs got stabilized and expanded due to improvements

like cold polymerization, oil extensions etc. Synthetic rubbers which can fully

C.O.E.& T.,Akola 1


2/32


or partially replace the natural rubbers are generally termed as general purpose

synthetic rubbers. Today we have an array of synthetic rubbers.

The second type of development involved considerations to have

those properties deficient in the natural rubber such as resistance to oil, heat,

ozone etc. to be eliminated. Thus developments of special purpose rubbers like

Nitrile rubber came on scene and has grown substantially.

C.O.E.& T.,Akola 2


3/32


SYNTHETIC RUBBER POSITION IN INDIA

At present consumption of all synthetic rubbers together is

approximately 22% of the total rubber consumed in India it is expected that

the synthetic rubber consumption in India can be as much as 40% provided

indigenous availability improves and import duties on rationalized for highly

specialized rubber which are not produced in India. Presently the synthetic

rubber scenario can be as under. Availability of monomers like butadiene,

styrene in the country will play significant role in promoting production of

general purpose rubbers like SBR, PBR in country. Though the SBR

production came in India 1963 by Synthetics and Chemicals Ltd it did not

grow with demand on natural rubber with its sustained growth supported the

growth of rubber industry.

Company Name Type PresentCapacity(MTA) Trade Name

Synthetics & ChemicalsLtd. SBR 40,000 Synaprene

APAR Industries ltd. NBR 10,000 Aparene

APAR Industries ltd. HSR 9000 Powerene

Unimers India ltd EPDM 6000 Herlene

NOCIL EVA 50000 Powerene

C.O.E.& T.,Akola 3


4/32


MONOMER SYNTHESIS

Nitrile Rubbers are co-polymers of Butadiene and Acrylonitrile.

A. Butadiene

Butadiene is a major monomer in production of NBR. Butadiene can

be manufactured by various routes. In past routes from acetylene (Berthelot,

REPPE process) ethylalcohol (Ostronislenksy, Lebdev process) has been used

in West. Even today in our country we are using alcohol as starting material

for the production of Butadiene. This can be shown as under :

CH 3 CH 2 OH CH3 CHO + H 2

2CH 3 CHO CH 3 CHOH CH CHO CH 3 CH==CH-CHO

CH 3 CH== CHCHO + CH 3 CH 2 OH CH3 CH==CHCH 2OH+CH 3 CHO

CH 3 CH == CH CH 2OH CH 2==CHCH==CH 2+H 2O

(Approx. 250 parts of Ethylalcohol gives 100 parts of Butadiene)

B. Acrylonitrile

B.1. Acrylonitrile synthesis from acytelyene and hydrogen cyanide Hydrogen

cyanide manufactured by Andrussor reaction as :

Feed ratio NH 3 : Natural gas : air is 11.2:12.0:76.8

2CH 2 + NH 3 +3O 2 HCN + 6H 2O

Addition of hydrogen cyanide to acetylene in presence of an aqueous

catalyst HCN

C.O.E.& T.,Akola 4


5/32


Catalyst (HCN)

Ammonium Chloride 21.1%

Cuprous Chloride 54.3%

37% HCL 1.4%

Water 23.2%

pH


6/32


Acrylonitrile monomer can also be synthesized from acetaldehyde and

hydrogen cyanide (KNAPSACK PROCESS). In Distillers process

acrylonitrile is synthesized from acrolein. First acrolein is produced from

propylene, by catalytically oxidized to acrolein. Acrolein in presence of

ammonia and air is converted to acrylonitrile as :

CH 2=CHCHO+NH 3+1/2 O 2 CH 2 = CHCN+2H 2O

This process which operates at elevated temperatures in presence of an

oxidation catalyst (Molybdic Oxide)

There are many other routes for synthesis of Acrylonitrile monomer,

but the above process is used in India by the only producer, i.e. IPCL.

The most popular route today use predominantly hydrogen-rich

straight-chain C4 units which results from petroleum (naphtha) cracking

which is shown below.

1. Butadiene Oil Naphtha Butadiene

2. Acrylonitrile Oil Naphtha Propylene + Ammonia & air Acrylonitrile

MONOMER SUPPLIERS

Gujrat Apar Polymer Limited.

National Organic Chemical Industries Limited.

Indian Petrochemical Corporation Limited.

Reliance Petrochemicals; Surat.

C.O.E.& T.,Akola 6


7/32


CHEMICAL STRUCTURE OF NBR

Chemical structure of NBR is generalized as copolymer of butadiene

and acrylonitrile as shown below

-----(CH 2-CH=CH-CH 2)x---(CH-CH 2)y-------|

CNToday the commercial grades are available with 16 50% of the

acrylonitrile (ACN) content. The chemical structure of NBR is very similar to

SBR. The replacement of benzene group by cinogen group introduces the

polarity in the molecule. The influence of this group enhances the properties

like oil, heat, air permeability resistance, electrical conductivity properties of

vulcanizates. However low temperature (Tg value) properties are affected with

increase in ACN content.

Like SBR, NBR can be vulcanized by conventional cure system based

on sulphur and accelerator or with organic peroxides. Polarity in the molecules

decreases electrical resistance of the polymer and bring it in antistatic range,

so that NBR can be compounded for products where dissipation of electrical

charges are essential e.g. textile cots and aprons.

NBR is amorphous in nature and needs reinforcing fillers like carbon

black, precipitated silica to develop physical properties such as tensile

strength, modulus, resistance to abrasion etc.

C.O.E.& T.,Akola 7


8/32


METHODS OF MANUFACTURING OF NBR

Nitrile rubbers are manufactured by Emulsion co-polymerization of

butadiene and acrylonitrile together. The stainless steel reactors are mirror

finished to exercise excellent temperature controls and entire latex production

is through the digital control system. Thus the addition of all ingredients and

reactions are automatically controlled. This ensures the excellent quality with

high consistency in properties of polymer manufactured. At present the

emulsion polymerization is carried out at 5 oC compaired to 50 o C in the earlier

days.

Nitrile rubbers are produced by

I ) Emulsion process :

a) hot polymerization -------------------- 50 o C

b) cold polymerization-------------------- 05 o C

II) Solution process--- this process has found limited applications so far

REACTION MECHANISM OF FREE RADIAL EMULSION

POLYMERISATION

Following are the three steps involved in this process :

1) Initiation 2) Propagation and 3) Termination

C.O.E.& T.,Akola 8


9/32


1. Initiation

ROOH + Fe 2+ ----------------------------------> RO* + Fe 3+ + OH -

Fe 3 + Sodium Sulfoxilate ---------------------> Fe 2+

RO* + CH 2 = CH - CH = CH 2 --------------> RO- CH 2-CH=CH-CH 2*

2. Propagation

RO - CH 2 - CH = CH - CH 2 * + CH 2= CH - CH = CH 2

----> RO - CH 2 - CH = CH - CH 2 - CH 2- CH = CH - CH 2* + CH 2 =CH|

CN

RO - CH 2 - CH = CH - CH 2 - CH 2- CH = CH - CH 2 - CH 2 -CH*|

CN

There is a random arrangement of monomer in the polymer, can be

represented as

------B-B-B-A-A-B-B-A-A-A------ A for AcrylonitrileB for Butadiene

3. Termination

S R R - || | |

RO* + S -C - N + H 2O ----------------> ROOH + CS 2 + NH| |

(From Hydroperoxides ) R R

Polymerization Reaction

CH 2 = CH - CH= CH 2+ CH 2=CH -----(-CH 2 - CH = CH- CH 2) x -----CH 2-CH-----------| |

CN CN y n

C.O.E.& T.,Akola 9


10/32


C.O.E.& T.,Akola 10

Emulsifier Initiator Activator Modifier

Refrigerant

Flow

DiagramofNitrileRubberManufacturing

Butadienerecycle

ACNrecycle

Coagulation

Water

SerumRecycle

WashWaterRecycle

Steam

Vent

FinishedProduct


11/32


Figure Index

1. Butadine Storage .

2. ACN storage .

3. Reactor .

4. Flash Tank .

5. Stripper .

6. Latex storage tank.

7. Coagulation tank .

8. Conversion tank .

9. & 9A Dewatering screens .

10.Wash Tank .

11. Dewatering Press.12.Shredder .

13.Dryer .

14.Baler .

15. Magnetic detector .

16.Film wrapping .

17. Bagging and stitching.

C.O.E.& T.,Akola 11


12/32


EMULSION POLYMERIZATION

The basic polymer recipe in addition to the monomers contains water,

stabilizers, emulsifiers, catalysts, activators, electrolytes and terminating

agents. The basic steps involved in the manufacture are polymerization,

coagulation, washing and drying.

In polymerization, the monomers are emulsified in water, a free radical

generating catalyst is added and the mixture is agitated while a constant

temperature is maintained. Following the polymerization cycle, the material is

transferred to a blow down tank in which the terminating agent is added to

control the molecular weight of the polymer according to the grade, the

residual monomers are removed. Then the latex is stabilized and coagulated

into fine crumbs by the addition of various coagulating agents like alum,acids, and salts. This is then washed, dewatered, and finally dried crumbs are

compacted to form the bales. Nitrile rubbers are available in several forms

such as sheets, crumbs, powers and liquids as per requirement.

POLYMERIZATION

NBR is produced from the emulsion polymerization of butadiene and

acrylonitrile at 5 0c for cold and 50 0c for hot process. Redox system of initiator

is used for cold while for hot process K 2 SO 8 is used. The monomer or is used

C.O.E.& T.,Akola 12


13/32


for cold while for hot process K 2 SO 8 is used. The monomer ratio and the

temperature at which polymerization are carried out are important features of

NBR manufacturing. The properties of product may also be influenced by

other things like amount and nature of modifiers and emulsifiers. The

conversion of monomer to copolymer is not carried out to completion for

quality reasons. The reaction is stopped at predetermined stage when desired

properties are obtained in the product. The unreacted monomers are stripped

from latex and recovered for the reuse in the stripper column. Following

parameters affects the polymer properties during polymerization.

1. polymerization temperature

2. emulsifier

3. modifier

1. Polymerization temperature

Polymerization temperature influences the branching, cross-linking, the

stereoregular configuration of the enchained butadiene units and the molecular

weight distribution of the polymer. In general the lower polymerization

temperature, the less branched and crosslinked is the rubber and lower will be

the gel content. In microstructure the proportion of vinyl groups in the

polymer varies little over the rang of polymerization temperature from -200c

to 1000c. By contrast, the balance between cis-1,4, and trans- 1,4 structure is

C.O.E.& T.,Akola 13


14/32


markedly affected by polymerization temperature, the ratio of cis and trans

falls as the polymerization temperature is decreased. The presence of

acrylonirtile unit has little effect upon the microstructure of the enchained

butadiene butadiene units. The improved mechanical properties of NBR

vulcanizate from cold process have been attributed to the greater structural

regularity caused by increased trans- 1,4 content as well as to the formation of

less branched and crosslinked structure in polymer.

2. Effect of emulsifier

Emulsion polymerization is a heterogeneous system. The

polymerization is carried out using water as a liquid or solvent but in

emulsion. The emulsifying agents are used for this purpose. It has two

portions, first is hydrophobic due to long hydrocarbon chain of emulsifier and

second is the hydrophilic due to the polar end (e.g. sodium or potassium

sulphonate) attached to the emulsifier carbon chain. Emulsifiers are hardly

soluble in water. There lies a critical concentration of the emulsifier called as

CMC. above which they are insoluble and forms insoluble spherical structures

called as micelle. Increase in emulsifier causes the formation of smaller

particles. The synthetic emulsifier having a low temperature water solubility

shows no tendency to gel even down to 5 0C due to their branched structure

their calcium and magnesium salts are more soluble. Therefore they shows

C.O.E.& T.,Akola 14


15/32


less tendency to be precipitated from hard water. For synthetic soap, rate of

polymerization increases linearly with the square root of the soap level.

3. Modifier

These are mercaptans, which are used to control molecular weight and

acts as a reaction transferring agent in the free radical reaction. It does not

effects the rate of polymerization. On increasing the modifier amount in

polymerization recipe, both polymer plasticity and gel content falls sharply.

C.O.E.& T.,Akola 15


16/32


VULCANIZATION

The vulcanizing agents are usually sulfur compounds, which react with

the polymer to produce a cross-linked material in which the linkages are -C-S x

-C-. The cross links may be mono-, di-, or polysulfidic. The type of linkage

is determined by the concentrations of sulfur, accelerators, and retardants, and

temperature. Most of the conditions to produce a given products are

empirical, but some advances in knowledge are beginning to allow a scientific

basis for vulcanizing conditions.

The accelerators reduce the time required for the vulcanization of

rubber from several hours to a few minutes. In addition, less sulfur is needed

and a more uniform product is obtained. The mechanism of accelerator action

is not well understood, in spite of much research, but presumably involves the

formation of an activated form of sulfur, which forms a "sulfur bridge" at

reactive sites within the rubber molecule, linking the large molecules into a

tight network structure. Most accelerators contain nitrogen and sulfur. Two-

thirds of all the accelerators made, consist of mercaptobenzothiozole (MBT)

and its derivatives.

Nitrile rubbers are some what similar to SBR's in comparison, however,

Sulphur is less soluble in NBR. Thus early addition of sulphur or sulphur

donor systems are more appropriate. Semi-EV and EV cure systems play a

C.O.E.& T.,Akola 16


17/32


special role in NBR vulcanization and provide high heat resistance & low

compression set. Like other diene rubber, Nitrile rubber is vulcanized by

sulphur cure system (S+Accelerator+ZnO). This can be depicted as below.

1. CH 2-CH=CH- CH 2 - CH 2 -CH -------->| -H -

CN

2. CH 2-CH=CH- CH 2 - CH 2 -C* + S n + Accelerator * -------->|

CNCN|

CH 2-CH=CH- CH 2 - C|

Sx|

CH 2-CH=CH- CH 2 - C|

CNThus cross-linking continues.

Conventional accelerator system such as MBTS, Sulfenamides, Dithio-

Carbamates, Guanidins have given best results. A good heat resistance is

easily obtained by using TMTD with low or no sulphur or a sulphur donor

(0.5phr). Cadmium oxide (0.25phr.) provides very high heat resistant

however very toxic in nature. Carboxylated NBR needs multifunctional

reagents such as ZnO or Zinc Peroxides. Curing of NBR is also common for

achieving better heat resistant properties with additional use of co-activators

C.O.E.& T.,Akola 17


18/32


such as EDMA(Ethylene Diamine Methacrylate) high hardness grades can be

produced.

However peroxide cures give lower tensile, tear, swell resistance &

poorer dynamic properties. They restrict flexibility in compound development.

Vulcanization can be achieved with Sulphur, Dioxide or peroxide system. As

with NR, SBR, ZnO at 3-5 phr. level & stearic acid at a 1-2 phr. level are

added for proper activation.

C.O.E.& T.,Akola 18


19/32


COMPOUNDING

Pure rubber (natural or synthetic) is usually not suitable for use. The

desirable properties of plasticity, elasticity, toughness, hardness or softness,

abrasion resistance, impermeability and the myriad combinations possible are

achieved by the art of the rubber compounder.

A broad range of properties can be obtained from properly

compounded Nitrile rubber. In general, NBR is compounded along lines

similar to those practiced with NR and SBR.

As mentioned earlier, selection of grade of rubber is very important

criteria depending on the oil and fuel resistance is required. Higher

acrylonitrile NBR rubber is chosen when high resistance is required. Lower

acrylonitrile rubbers are used when low temperature and dynamic properties

are important. Activation system generally used contains 3-5 phr of zinc oxide

with 1-2 phr of stearic acid. This system is used along with sulphur donor

vulcanization system. With peroxide curing system cynurate (Tac) can be used

as activator.

Unlike natural and polychloroprene rubbers, NItrile rubbers does not

crystallize on stretching (self reinforcement) and therefore is a balanced

reinforcing system. When used alone, low reinforcing carbon blacks are

preferred as the highly reinforcing blacks which tend to stiffen the uncured

C.O.E.& T.,Akola 19


20/32


stock as vulcanizate and pose problems during processing. Consequently high

reinforcing carbon blacks are used mainly at low loadings or in conjunction

with the less reinforcing fillers. Non-black application will require the use of

reinforcing silicas of various types of calcium carbonates hard clays, talc and

other pigments. Silicas are capable of imparting properties as good as carbon

black barring compression set and resilience. Nitrile rubbers needs proper

choice of antioxidants to perform under heat, air and ozone. Ozone resistance

can be improved by blending it with PVC, EPDM and Epichlorohydrine.

In summarizing Nitrile rubbers can be compounded with :

a) filler types: carbon blacks, silica, silicates, alumina

b) plasticizers: esters, polymeric esters, aromatic oils and resins

c) cure systems: ebonite conventional sulphur and peroxidesADDITIONAL DATA ON COMPOUNDING

Pure rubber (natural or synthetic) is usually not suitable for use. The

desirable properties of plasticity, elasticity, toughness, hardness or softness,

abrasion resistance, impermeability, and the myriad combinations possible are

achieved by the art of the rubber compounder. A typical rubber compound is

shown in Table .

C.O.E.& T.,Akola 20


21/32


Table - Typical Rubber Compound

Ingredient PartsRubber

Sulfur

Zinc oxide

Stearic acid

Accelerator

Loading or filling pigment

Reclaim, softeners, extenders, colors, blowingagents, antioxidants, antiozonants, odorants,

etc.

100.0

2.0

5.0

3.0

1.5

50

As required

1. Selection of NBR Grade : In formulating compound, one of the important

step is to select correct grade of rubber, to meet and product

specifications/requirements.

The major variables which permit various grades are :

a) Type of Soap Fatty Acids, FattyAcids/Rosin Acids, Synthetic

b) Mooney value 20 ML - 80 ML

c) ACN Percentage 18% - 50%

d) Types of stabilizer Staining, Non-staining

e) X-linked polymers

2. Selection of Reinforcing Filters :

C.O.E.& T.,Akola 21


22/32


NBRs are like SBR in amorphous character, and being unable to

crystallize on stretching requires presence of reinforcing fillers to attain good

physicals. Carbon blacks and silica fillers are major fillers used for improving

physicals. In carbon black one can use right from SAF. ISAF mix , down

upto MT blacks. Fine particle blacks are difficult to disperse and gives tough

compounds to process. Thus softer and medium blacks like FEF, GPF, SRF,

MTS are used. FEF is selected as the name indicates for Fast Extrusions.

The effect of SRF-HM is given below to give guidance of physicals it imparts

LoadingCB

Plasticizer T.S.(psi)

Elongation.@Break

Hard-ness

300% Mod(psi)

Angle Tear lbs/In.

25 phr 10

20

2200

2000

550

600

55

50

650

500

250

210

3. Curatives :

Normal accelerator, sulphur combination is NBR 100, MBTS or CBS

1.5, Sulphur 1.5. For improved compression set, heat resistance EV systems

are used. EV cures affect tear and flex properties of the vulcanizate.

Vulcanizates, which have been made with TMTD with little or no

sulphur, tend to 'bloom' because of the high dosage, but this can be reduced or

even eliminated by simultaneous use of MBT, MBTS or CBS. Then too, the

blooming can be suppressed by the partial replacement of the TMTD with

another thiuram disulphide. NBR can be cured with peroxides giving better

C.O.E.& T.,Akola 22


23/32


heat and compression set properties. The following characteristics are attained

with nitrile rubber compounds optimally prepared with dicymyl peroxide.

a) Good tensile strength at room temperature but relatively lower values at

elevated temperatures,

b) Low elongation at break,

c) High modulus

d) Low permanent set at break,

e) Moderate tear resistance at room temperature and very low values at higher

temperatures,

f) Excellent performance under dynamic loading with the Goodrich flexometer

and in ball fatigue testing,

g) Low compression set especially in hot air at high temperatures and in hotoils.

h) Very good aging in hot air,

i) Good aging in steam and hot oils, and

j) Relatively strong swelling when kept in boiling water.

4. Selection of Plasticizers :

Nitrile Rubbers are polar (due to ACN) and hence only aromatic/highly

a aromatic oils/plasticizers are compatible. The most common plasticizers are

C.O.E.& T.,Akola 23


24/32


DBP/DOP types. Adipates/sebacate ester plasticizers are used when low

temperatures flexibility is desirable. Paraffinic and Naphthanic oils should be

avoided as it would tend to 'exdue' from the vulcanizate. The recent trend is

supply DBP/silicate blend (e.g. E-2 Mix DBP from C.P. Hall) to facilitate easy

addition. When flame retardance is required Triaryl/Trieresyl phosphate is

added.

NBR is a polar rubber and hence for better compatibility only aromatic

plasticizers and its compounds (with high polarity) are used. The plasticizers

have far reaching effect on NBR vulcanizate. The mol. wt. also has an

important effect on its plasticizing action. Thus, the viscosity of the

compound the physical properties of the vulcanizates are largely dependent on

the type and the amount of the plasticizer.Plasticizers are added to improve processing, impart tackiness, improve

low-temperature performance and to lower hardness of the vulcanizate.

Plasticizers also assist in filler dispersions during mixing. Esters of carboxylic

acid or phosphoric acid are most suitable in compounding NBR. These can be

either monomeric or polymeric in nature. Monomeric plasticizers get easily

extracted, when in contact with oils.

All plasticizers decrease the viscosity and the elastic recovery forces of

unvulcanized NBR and these increase with increasing easing amounts. The

C.O.E.& T.,Akola 24


25/32


degree of reduction is especially variable in magnitude. Plasticizers can be

classified in two different groups, depending on whether they have a strong or

weak effect on the elastic, restoring forces.

Fats, waxes, resins, and polymeric plasticizers belong to one group. In

general, they strongly reduce the resilience of the vulcanized compounds and

thus exert a most favorable effect on processibility; that is to say, they

improve the calendar ability, extrudability and building tack.

Stearic acid, wool fat and some others of this group are relatively

poorly compatible and, therefore, may readily sweat out if sued in too high

concentrations and cause trouble in building operations. This same thing

holds, as has been said, for petroleum plasticizers which are high in aliphatics.

The molecular weight of the plasticizer is significant for compatibility.Easter and ether plasticizers are typical representatives of the other

group. They work by solvation, in the previously given sense, swelling the

NBR compounds strongly and causing pronounced softening. Actually they

lower the elasto-recovery forces relatively little. Because of their ability to

increase the elasticity of the vulcanisates, they are usually referred to an

"elastomers".

Certain viscous xylene-formaldehyde resins, alkyd resins, aldol resins

as well as rosin, Koresin, coumarone resins and swell-resistant and liquid

C.O.E.& T.,Akola 25


26/32


factices, have found value as processing aids for improving calendarability

and extrudability as well as the building tack. Viscous butadiene/acrylonitrile

copolymers (10,000-300,000 cp) also serve very well. Being the same type of

material, they do not tend to sweat out when used in large amounts and thus

are oil resistant and non-volatile at higher temperatures.

PROCESSING

Nitrile rubber compounds are fabricated into a wide variety of articles

requiring many different types of processing involving milling, internal

mixing, extrusion, calendaring and vulcanizing in many different ways. All of

C.O.E.& T.,Akola 26


27/32


commercially available Nitrile rubber can be mixed either on a two rollmill is

of no exception. The only care taken during mixing is the addition of sulphur

immediately after rubber has formed smooth band on the roll.

Compounds can be designed to be easily extruded, calendared or

molded with injection, compression, or transfer techniques. Optimum

breakdown and dispersion are required for both calendaring and extrusion,

sometimes requiring remilling operation, at least 16 hrs after original mixing.

In extrusion the screw and barrel should be at about 60-70 0c with head at

about 90 0c and die in the region of 120 oc. While for calendaring conditions,

for unsupported sheet, coating or plying are generally as follows:

Top roll ------ 75-85 o c Middle roll------ 60-70 o c Bottom roll----- 75-85 o c

For excellent extrusion, high Mooney viscosity rubber is chosen particularly when high green strength is required. Low or medium Mooney

viscosity polymers will lend excellent calendaring characteristics molding of

Nitrile rubber can be carried out conventional way and at conventional

operating conditions.

VERSATILITY IN NBR GRADESWide range of ACN content (16-50%).

16%, 20%, 23% ACN, for Very Low Temperature Service.

26%, ACN, with Carboxylation, for improved abrasion.

C.O.E.& T.,Akola 27


28/32


27%, 29% ACN ,for Low Temperature Service.

33% ACN ,For General purpose use.

39% ACN ,For Fuel ,Oil, High Temp and Oil Drilling application .

40% ACN, For Fuel ,Oil, High Temp and Freon resistance application.

45% ACN, For Fuel, Freon and High Temp. Service products.

INCREASE IN ACN CONTENT LEAD TO THE FOLLOWING

1. Improves resistance to fuels and oils.

2. Increases abrasion resistance and hardness.

3. Improves tensile strength and modulus.

4. Improves processing behaviour.

5. Increases permeability resistance to gas diffusion.

6. Decreases Low temperature flexibility.

7. Reduces Resilience and Elasticity.

8. Improves heat resistance.

9. Decreases electrical insulation resistance.

10. Increases compatibility with polar plastics.

PROPERTIES OF NBR

1. Excellent resistance to Oils & Fuels.

2. Excellent resistance to Abrasion & wear.

C.O.E.& T.,Akola 28


29/32


3. Good heat and chemical resistance.

4. Low permeability to air & gases.

5. Excellent overall physical properties when compounded with

reinforcing filler.

6. Low electrical insulation resistance, hence excellent Anti-static

properties.

7. Excellent compatibility with PVC; NBR/PVC fluxed properly displays

excellent resistance to ozone and weather.

8. Blends with PVC permits developments of TPEs. suitable for many

applications including footwear soling, gas tubing, garden hoses etc.

9. Excellent compatibility with Phenol-formaldehyde resins. Such blends

are useful for adhesives, high hardness products, leather like products etc.

C.O.E.& T.,Akola 29


30/32


APPLICATIONS OF NBR

NBR is one of the most widely consumed rubber worldwide. It's

applications in different fields are discussed below.

1) In Military applications : Increase in ACN content of NBR improves

resistance to fuels and oils with increased abrasion resistance. Hence it is used

for manufacturing fuel, hydraulic, pneumatic hoses, diaphragms, oil seals,

valves, abrasion resistance soles, combat boots and engine mounts.

2) Automotive applications : NBR is prone to have excellent resistance to

fuels and oils, so it is used advantageously used for manufacturing of fuel

hose, oil seals, ('O' rings), 'V' packings, crash pads, hydraulic hoses, power

stearing hose and pressure bellows.

3) Industrial applications : Variety of grades of NBR can be obtained with

varying heat resistance depending on ACN contents, so NBR is used for

manufacturing water pipe insulations, cots & aprons, gaskets & friction material.

NBR is having low electrical insulation resistance hence excellent

antistatic properties and liable to be used for conveyor beltings.

4) Commercial applications : Commercial applications include food and

solvent handling hoses and Belts, Rice Rolls, Printing Rolls, Adhesive, Shoe

Soles, Milking Inflations, Floorings, Astro-turf underlays, Hawai Chappals,

Printing blankets and Blocks.

C.O.E.& T.,Akola 30


31/32


CONCLUSION

So our country has been using the NBR and it should gather higher uses

as there is increase in availability in NBR indigenously. Some latest

advancements in the field and NBR technology are also taking place like

1) Emergence of carboxylated NBR

2) Halogenated NBR

3) Nitrile rubbers containing based antioxidants

4) NBR-Polyolefin blends (NBR+PVC)

5) NBR in powder form.

Importantly NBR can be efficiently used for the manufacture of various

molded products due to its excellent processibility & easy of availability. It

should replace the applications of some inferior rubbers, also new applications

should be bourn for nitrile rubber.

C.O.E.& T.,Akola 31


32/32


BIBLIOGRAPHY

C.M. Blow & C. Hepburn : " Rubber Technology and Manufacture "

(2nd Edition) Butterworths P.N. 130-137

Maurice Morton : " Rubber Technology "

(3rd Edition ) Van Nostrand Reinhold Newyork P.N. 322-338

Harry Barron : " Modern Rubber Chemistry"

D Van Nostrand Company.inc Newyork P.N. 303-318

J.Y. Brydson : " Plastic Materials "

(6th Edition) Butterworth Heinemann Publication P.N. 267-268

Industrial Manual of APAR INDUSTRIES LIMITED, Mumbai.

WEBSITES

www.aparindustries.com

www.azon.com

industrial manufacturing of nitrile rubber

Documents