CRB 30204 RUBBER TECHNOLOGY – CHAPTER 1 Nurul Iman Abdul Razak

Chapter Outline Types of rubbers and their application

Natural Rubber (NR) From Hevea brasiliensis tree. Structure:

NR Latex concentrate: Dry Rubber: Centrifuged latex Creamed latex Evaporated latex Dry Rubber: Ribbed Smoked Sheets (RSS) Air-dried Sheets Pale Crepes *Conventional Grades

Technically Specified Rubbers (TSR) TSR were first introduced into the market by Malaysia in 1965 as the Standard Malaysian Rubber (SMR). SMR graded by: source of the rubber properties There are: SMR L SMR CV SMR GP SMR 10,20 & etc.

SMR L light-coloured rubber from high quality of field latex superior heat ageing resistance excellent vulcanizate  properties high TS, E & EB

Application ideal choice for production of light-coloured / translucent products such as: shoe soles pressure-sensitive tapes surgical and pharmaceutical products industrial printing rollers gaskets

SMR CV CV : constant viscosity produced from high quality field latex, has a Mooney viscosity stabilized within a narrow range generally softer than the non viscosity-stabilized grades, it increases the productive capacity of mixing equipment.

Application of SMR CV high quality products mechanical mountings for engines and machinery bridge bearings vehicle suspension systems large truck tire treads, conveyor belt covers cushion gum for tire retreading masking tapes injection molded products including rubber/metal bonded components industrial rolls rubber cements. *It is frequently blended with other grades of NR to optimize cost and balance of other properties such as viscosity.

SMR GP: general purposes Made from 60:40 mixture of latex-grade sheet rubber and field coagulum. Dark colored rubber Application: Make it suitable for tire production Plasticizer in SMR GP gives beneficial to tire manufacturers.

SMR 10 Produced from clean and fresh field coagulum of from sheets that have not been through the smoking process. Application: It can be used for tires cushion gum stocks joint rings by injection molding microcellular sheets for upholstery and packing conveyor belts footwear.

SMR 20 Application: It is produced mostly from field coagulum Its low viscosity and easier mixing characteristic Application: It is used mostly for tires cushion gum stock bicycle tires micro-cellular sheet for upholstery and packing conveyor belts footwear and other general products.

Other forms of natural rubber Oil-extended Natural Rubber (OENR) Deproteinised Natural Rubber (DPNR) Peptised Rubber Powdered Rubber Superior Processing Rubbers (SP) Heveaplas MG Rubbers (MG) Epoxidized Natural Rubber (ENR) Thermoplastic Natural Rubber (TPNR)

Product Applications Tyres In passenger-car bias-ply tyres, NR is used only in the carcass as well as the side walls, where the hot tear resistance, adhesion and tack of NR are used to advantage. In commercial vehicles, the amount of NR used increases with the size of the tyre. In large earthmover tyres, for example, almost 100% NR is used due to the requirements of low heat generation and high cutting resistance. Natural rubber is used in blends with halobutyl rubbers in the inner liner tubeless tyres.

Mechanical Goods (Industrial Products) This include a large variety of products such as hose, conveyor belts, rubber linings, gaskets, seals, rubber rolls, rubberized fabrics, etc. In these products, the choice of elastomers is made on the best compromise between price and performance.

Engineering Products The softness of a natural rubber component in different directions may be varied independently by the judicious use of shape effects. In dynamic applications such as springs, and vibration mountings, bushings, and so forth, high fatigue resistance, good strength, and durability are additional points in favour of NR. In other applications such as bridge bearing, factors such as weathering, ozone resistance, and low temperature flexibility are also important. NR is now accepted as suitable for use in bridge bearings, in place of, neoprene.

Latex Goods NR latex has now been largely replaced by polyurethane in foam for upholstery and bedding. The main uses of latex are in dipped goods, foam, carpet backing, thread and adhesives.

Footwear Natural rubber is extremely suitable for rubber footwear manufacturing. Its use is limited only by cost.

STYRENE-BUTADIENE RUBBERS (SBR) Raw Materials The chief raw materials required to manufacture SBR are butadiene and styrene. Structure:

Application: Elastomer SBR: pneumatic tires shoe heels and soles gaskets chewing gum Emulsion SBR: coated paper as a sealing and binding agent behind render

BUTYL RUBBER Low rates of gas permeability. Thermal stability. Ozone and weathering resistance. Vibration damping and higher coefficients of friction, and Chemical and moisture resistance.

Applications Gas Permeability A passage of gas is a function of the diffusion gas molecules through the membrane and the solubility of the gas The Polyisobutylene of the butyl molecule provides a low degree of permeability Butyl is at least 8 times better than NR in air retention.

air barriers for tubeless tires air cushions pneumatic springs accumulator bags air bellows

Ozone and Weathering Resistance Ozone and weather resistance, the least unsaturated butyl is advantageously. Preferred for electrical applications needing ozone resistance, and in rubber sheeting for roofs and water management systems. High quality electrical insulation.

Vibration Damping Automotive suspension bumpers. More highly damped butyl compositions more effectively control vibrational forces. In theory, more highly damped systems will less effectively isolate vibration at very high frequencies. In practice, dynamic stiffness becomes a controlling factor governing transmissibility.

electrical insulation and rubber sheeting for outdoor use Chemical and Moisture Resistance. electrical insulation and rubber sheeting for outdoor use elastomeric seals for hydraulic systems using synthetic fluids After 13 weeks immersion in 70% sulfuric acid, a butyl compound experiences little loss in tensile strength or elongation. Under similar conditions, natural rubber or SBR will be highly degraded.

ETHYLENE PROPYLENE (EP) RUBBER highly resistant to ozone and oxidation excellent heat resistance and weatherability have varying degrees of heat and oil resistance and elasticity;

Coolant hose (automotive) Applications Coolant hose (automotive) Variety of industrial: air and water hose and for phosphate and ketone service. Insulation in power cables and ignition wiring Cable covers Underground wire and connector Coated fabrics and sheet goods As viscosity modifiers in lubricating Automotive: coolant hose for its excellent water and coolant resistance. variety of industrial: air and water hose and for phosphate and ketone service. insulation in power cables and ignition wiring cable covers where abrasion and heat but not oil resistance is required. underground wire and connector due to its water resistance. coated fabrics and sheet goods where the largest volume goes into moisture barriers and one-ply roofing. as viscosity modifiers in lubricating oil to improve low temperature impact strength of PE and PP.

NITRILE RUBBERS (NBR) Nitrile rubbers basically are manufactured by emulsion copolymerization of butadiene with acrylonitrile in process similar to SBR. The basic reaction is as follows:

good resistance towards nonpolar oils, fats, and solvents. Application good resistance towards nonpolar oils, fats, and solvents. used in automotive and oil industry like oil seals and automotive hydraulic hose. better heat resistance than CR but they are subject to ozone cracking

CHLOROPRENE RUBBERS also known as neoprene resistance towards a wide variety of animals and vegetables fats and oils, waxes, and greases and also aliphatic hydrocarbons. good resistance to ozone attack, air oxidation, or weathering ability to retard flame, have tendency to self extinguish when flame source is removed. has high level of resistance to flex cracking.

Application: used for hose, belts, wire and cable covering, coatings, sheeting and adhesives

CHLOROSULPHONATED POLYETHYLENE RUBBERS, CSM CSM is obtained by reacting polyethylene in solution with chlorine and sulfur dioxide. Structure:

comparable with chloroprene rubber but it has better resistance to acids, solvent, ozone, oxidation and better color stability. very good resistance towards flex and abrasion, excellent resistance to oxidation aging, weathering, acids and alkali, and moderate resistance to oil and gasoline. poor resistance to aromatic solvent, flexibility at low temperature is limited and moderate compression set and resilience. Application: roofing, pond liners and applications that need resistance to strong mineral acids.

POLYACRYLIC RUBBERS, ACM Better resistance but poorer low temperature resistance compared with polybutylacrylate. High temperature resistance up to 200°C & good resistance to oil, ozone, sunlight and weathering Resistance to swelling and deterioration by hot hydrocarbon oils, extreme pressure lubricants, and transmission and hydraulic fluids

Heat are superior to those of NBR. Resistance to water and chemicals containing hydroxyl groups Application automation engine and transmission seals gasket and 0-rings.

FLUOROCARBON RUBBERS (FKM) The best known rubbers are those by the name Viton. excellent resistance to oils, fuels, lubricants and most mineral acids and also resist many aliphatic and aromatic hydrocarbons like carbon tetrachloride and xylene. These rubbers are flame resistant and do not support combustion.

poor resistance towards some polar solvents like low molecular weight esters and ethers, ketones, certain amines, hot anhydrous hydrofluoric acid and certain proprietary hydraulic fluids) Applications of FKM include automotive fuel hose lines seals flue duct expansion joints

SILICONE RUBBERS Inert chemically, with no taste or smell, unaffected by atmospheric expose and do not show ozone cracking with excellent electrical insulation and high permeability to gases. Mechanical properties TS are low but change very little when measured at higher temperature (150°C). Its abrasion and tear strength are also poor

Oil resistance is about the same as that of chloroprene rubbers but poor resistance to acid and alkali, oil, gasoline and solvent. The cost of the raw rubber is higher than most rubbers Application: in aerospace, medical, food contact, and automotive ignition cable.

POLYURETHANE RUBBERS Resistance to ozone, oil, and oxidation and good aging properties. It also has good TS, tear strength, excellent abrasion and high toughness. However, they do suffer from limited resistance to hydrolysis.

Application door frames, window headers, medallions rosettes.

POLYSULPHIDE RUBBERS Polysulphide rubbers also know as "Thiokol“ low permeability and good resistance to weathering. poor physical properties, often with unpleasant odor but outstanding oil, solvent and chemical resistance.

Application fuel hose and tubing and as binder and for printing rollers Liquid polymers are useful as caulking compounds and sealants and as castable rubbers, e.g. encapsulation.

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