SYNTHETIC RUBBERS

IN TYRE AND

AUTOMOTIVE

INDUSTRIES

Professor Dr. Azemi bin SamsuriProfessorInQKA, UiTM, Shah Alam

DirectorANURAZ Enterprise

TOPICS OF PRESENTATION

• General introduction to synthetic rubbers

• Styrene Butadiene Rubber (SBR)

• Polybutadiene Rubber (BR)

• Polyisobutylene Rubber (Butyl Rubber)

• Nitrile Rubber (NBR)

• Polychloroprene Rubber (CR)

• Ethylene Propylene Rubber (EPM) and

• Ethylene Propylene-Diene Rubber (EPDM)

• Final Remarks

GENERAL INTRODUCTION TO SYNTHETIC RUBBERS

• Synthetic rubbers were introduced in the 1940s as a consequence of the

shortages of NR supply due to the spreading of war in the Far East

• Currently there are more 27 types of synthetic rubbers commercially

available

• Synthetic rubbers are manmade by polymerization process

• Early part of the production of synthetic rubbers were based on free radical

polymerization such as emulsion polymerization

• Later new types of polymerization appeared with the advantages of giving

better control of microstructure, molecular weight, molecular weight

distribution, and stereoregularity can be met to meet specific requirements.

• Other types of polymerization are ionic ,coordination, bulk, solution and

suspension polymerization.

• The advantages of synthetic rubbers over NR are cleanliness, consistency,

low molecular and viscosity thus, do not require pre-mastication process

STYRENE BUTADIENE RUBBER (SBR)

SBR - PROPERTIES & MAIN APPLICATIONS

• Solution polymerize SBR is more preferred to cold emulsion SBR

• SBR offers certain processing advantages compared with NR in

terms of consistency and purity which leads to more uniform mixes

and reduce batch-to-batch variations compared to NR.

• SBR usually produces better finishing of the extrudate profiles than

NR.

• SBR is widely used in tread compound of a tyre because it offers

excellent abrasion resistance and wear resistance.

• About 70% of SBR production goes into the tyre industry.

• The other applications of SBR include wire and cable, mechanical

goods, footwear and shoe, foamed products, hose

SBR - MAIN PROBLEM IN LARGE TYRES IS

ASSOCIATED WITH BLOWOUT FAILURE

POLYBUTADIENE RUBBER (BR)

• Today commercial polybutadienes are made almost exclusively by

solution polymerization processes.

• BR is synthesized ionically or via Ziegler-Natta catalysis capable of

control of microstructure, molecular weight distribution, and

branching.

• The BR produced represents a compromise between processability

and performance.

• Narrow molecular weight distribution and linearity, favour low

hysteresis loss, high resilience, and high abrasion resistance.

• There are at least three types of BR commercially available in the

market base on these three catalysts (i) titanium (ii) cobalt (iii) nickle-

based catalyst.

CHEMICAL STRUCTURE OF BR

BR – PROPERTIES AND APPLICATIONS

• BR has a very low glass-transition temperature, its Tg is about -

100oC.

• Because of its low Tg, BR has a very high resilience, low heat build-

up and low hysteresis.

• Thus BR is suitable for applications that require high resilience such

as for making golf, squash and tennis balls.

• BR is also widely used in truck and bus tyres where it is blended

either with NR or SBR to make tread compounds where its low Tg is

necessary for low heat build-up.

• BR also provides excellent wear resistance in tyres.

• The low Tg of BR makes it suitable for low temperature application

where low temperature flexibility is desired. Thus BR is blended with

PVC to improve low temperature flexibility of PVC pipes during

winter

Butyl Rubber (Isoprene Isobutylene Rubber, IIR)

• IIR is produced by cationic polymerization at very low

temperature of -100oC. The catalyst used is aluminum

chloride.

• The amount of isoprene unit in the chain is very little;

amounting to 0.6-2.5 mole % isoprene or roughly 2

mole percent unsaturation.

• This means that for every 98 moles of isobutylene,

there is present in the molecule 2 moles of isoprene.

• The main drawback of the ordinary butyl is associated

with its very slow cure as a consequence of its very low

unsaturation.

Butyl Rubber (Isoprene Isobutylene Rubber, IIR)

HALOGENATED BUTYL• The main drawback of the ordinary butyl is associated with its very

slow cure as a consequence of its very low unsaturation

• To overcome that problem halogenated butyl was introduced. The

introduction of a small amount of halogen either chlorine or bromine

serves two main functions;

• To amplify the reactivity of the functional units of the butyl molecule

without changing markedly the basic properties inherent of the

ordinary butyl

• To increase the possibilities for vulcanization. It is now possible to

use metallic oxides such as zinc oxide and magnesium oxide as the

crosslinking agents

• The major applications of butyl and halogenated butyl are in the

manufacturing of bladders, tubeless tyres, tubes, closures where the

low permeability (high impermeability) is of prime importance.

NITRILE RUBBER (NBR)Nitrile rubber (NBR) is produced by emulsion polymerization. It is a

copolymer consisting of polybutadiene units and acrylonitrile units. The

starting monomers are butadiene and acrylonitrile

The acrylonitrile (ACN) content varies from 18%, 33.3% and up to 50%

so that NBR can be classified into three grades having low, medium

and high ACN content

NITRILE RUBBER (NBR)Nitrile rubber (NBR) is produced by emulsion polymerization. It is a

copolymer consisting of polybutadiene units and acrylonitrile units. The

starting monomers are butadiene and acrylonitrile

NITRILE RUBBER (NBR) - Applications

• NBR having high and very high ACN is used in

applications where the utmost oil resistance is required

such as oil well parts, fuel cell liners, fuel hose.

• The medium grades are used where the oil is of lower

aromatic content or where greater swelling of the rubber

is tolerable.

• The low and medium low ACN grades are used where

low temperature flexibility is of greater importance than

oil resistance

NITRILE RUBBER (NBR) - Applications

NITRILE RUBBER (NBR)

• Carboxylated NBR – to improve other properties

such as tensile strength, modulus, hardness

and abrasion resistance while retaining the

excellent oil resistance of NBR.

• Hydrogenated NBR – to improve the heat and

oxidation resistance while retaining all the good

oil resistance of NBR

POLYCHLOROPRENE RUBBER (CR)

Research work which leads to the discovery of polychloroprene rubber (CR)

dated back as far as 1930 and its production started in 1931. It took more than

forty years of research and development work to perfect the production method

and manufacture. By the beginning of the 1970’s, there were at least seven

manufacturers with E.I. du Pont de Nemours as the leading manufacture.

POLYCHLOROPRENE RUBBER (CR)

• Polychloroprene rubber is considered as an all rounder

because of its wide scope of properties such as high

mechanical strengths, good oxidation and ozone

cracking resistance, good flame resistance, its polarity

offers good oil resistance and very good bonding to

metal

• Whilst the high degree of crystallinity offers very strong

adhesion to substrate

• Thus the application and end products of CR are wider

than any other synthetic rubbers

• Some important uses of CR are adhesives,

transportation industry, wire and cable, construction

industry, hose and belting

POLYCHLOROPRENE RUBBER (CR) – Properties and

Applications

• Polychloroprene rubber is considered as an all rounder because of

its wide scope of properties such as high mechanical strengths,

good oxidation and ozone cracking resistance, good flame

resistance, its polarity offers good oil resistance and very good

bonding to metal

• Whilst the high degree of crystallinity offers very strong adhesion to

substrate

• Thus the application and end products of CR are wider than any

other synthetic rubbers

• Some important uses of CR are adhesives, transportation industry,

wire and cable, construction industry, hose and belting

Ethylene Propylene Rubber (EPM)

The thermoplastics characteristics of both PE and PP can be turned

into rubbery state by destroying the chain regularity through

copolymerization so that crystallization is inhibited.

Indeed by copolymerizing ethylene and propylene with certain catalysts

of the Zeigler-Natta type can produce amorphous and curable polymers

known as Ethylene Propylene Rubber

LIMITATIONS OF EPM

• The main drawback of EPM is its inability to be

vulcanized with sulfur since it is fully saturated.

• To satisfy the rubber industrial needs Ethylene Propylene

Diene Rubber (EPDM) was introduced.

• As the name implies, EPDM is essentially a terpolymer

containing ethylene (E), propylene (P) and diene (D)

units, and M refers to the methylene which are the

repeating units (CH2).

Ethylene Propylene Diene Rubber (EPDM)

EPDM retains all the basic properties of EPM but with an added

advantage that the diene units serve as curing sites for sulfur

vulcanization. The presence of the double bonds does not seriously

affect the oxidation and ozone cracking resistance since the double

bonds are not situated on the main backbone chain.

EPM & EPDM – Properties and Applications

• EPM has an excellent oxidation and ozone cracking

resistance since there is no double bond for the oxygen

and ozone to attack

• This makes EPM as an excellent weather and heat

resistant polymer

• For these reasons EPM is widely used to make

automotive components such as wind screen seals,

wiper blades, gaskets for the engine, exhaust hanger,

steam hose etc.

• EPDM still having the properties inherited in EPM but

having the advantage of using sulphur as the

crosslinking agent.

FINAL REMARKS

Synthetic rubbers play some vital roles in tyre and

automotive industries.

THANK YOU FOR YOUR

KIND ATTENTION!