CRB 30204 RUBBER TECHNOLOGY – CHAPTER 1

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:
• 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:
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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:
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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
•
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•
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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:
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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
– It is produced mostly from field coagulum
– Its low viscosity and easier mixing characteristic
• Application:
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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.
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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.
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;
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
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:
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.
THANK YOU