Material Properties of Rubber

Fluorocarbon is a well- known high performance rubbers, especially it has excellent resistance to high temperature, ozone, weather, oxygen, mineral oil, fuels, hydraulic fluids, aromatics and many organic solvents and chemicals. Now we can supply rubber compound made by Viton® system gum like general type (A-TYPE, 66% fluorine) middle fluorine content type (B-, GBL-TYPE, 67~68.5% fluorine), high fluorine content type (F-, GF-TYPE,70% fluorine ), improving low temperature flexibility type (GLT-, GFLT) and excellent resistant to more chemicals and solvents-- Viton® ETP Extreme.

Hydrogenated Nitrile is a synthetic polymer that is obtained by saturating the hydrocarbon chains of Nitrile rubber with hydrogen. This special hydrogenation process reduce lots of double bonds in main chain of NBR polymer, so HNBR possess superior heat, ozone, chemical resistance and mechanical characteristics over standard Nitriles.

Natural rubber is produced from the latex of the Heveabrasiliensis, the chemical name of polymer is polyisoprene. Polyisoprene also can be synthesized by polymerization from its monomer isoprene. Natural rubber possesses many excellent physical properties including high resilience and strength, good abrasion resistance. The defects are like SBR, having poor resistant to hydrocarbon oil and not suitable in UV, oxygen, ozone because the double bond in the polymer backbone. But its poor weathering resistance can be modified by special additive.

Copolymers of butadiene and acrylonitrile are known by several generic names, Buna N, Nitrile Rubber and NBR. The acrylonitrile content of NBR compounds varies considerably (18% to 50%) and influences the physical properties of the finished material.

The higher the acrylonitrile content, the better the resistance to oil and fuel. At the same time, elasticity, compression set resistance to low temperature is adversely affected. The lower acrylonitrile content obtains, the better low temperature resistance, but sacrifice some resistance to oil and fuel. In view of these opposing realities, a compromise selection is the medium acrylonitrile content rubber. NBR has good mechanical properties when compared with other elastomers and high wear resistance.

NBR is not resistant to weathering and ozone. Some special compound can improve this defect or use NBR/PVC blending compound which has excellent weathering and ozone resistance and good resistant to fuel but compression set is not so good.

EPM is a Copolymer of ethylene and propylene, EPDM is terpolymer of ethylene and propylene with a small amount of a third monomer (usually a diolefin) to permit vulcanization with sulfur. Generally Ethylene Propylene Rubber posses excellent resistance to ozone, sunlight and weathering, and have very good flexibility at low temperature, good chemical resistance (many dilute acids and alkalis, polar solvents), and good electrical insulation property.

The millable Polyurethane rubbers are distinguished two types; one is polyester urethane (AU), the other is polyether urethane (EU). AU type urethanes have outstanding oil, fuel and solvent resistance but can be attacked by hydrolysis, EU type urethanes are not attacked by hydrolysis and still offer a fuel and oil resistance comparable to low ACN ( 18~22% ACN) nitriles or HNBRs. Any types polyurethane all have excellent wear resistance, high tensile strength and high elasticity in comparison with any other elastomers.

The most widely synthetic rubber in the entire world is SBR, a copolymer of styrene and butadiene. The most part of SBR rubber is used in tire by blending with natural rubber and butadiene rubber. SBR is weak and unusable without reinforcement by carbon black, but with carbon black it is strong and abrasion–resistant. The defects of SBR are poor resistant to oil and not suitable in weathering, UV, oxygen, ozone because the double bond in the polymer backbone.

Chloroprene was one of the first successful synthetic elastomers in 1931 by Dupont. It is prepared by emulsion polymerization of chloroprene, or 2-chlorobutadiene. CR is a multi-purpose elastomer which yields a balanced combination of properties. It has good resistant to sun, ozone, weather and perform well in contact with oils and many chemicals. It also display outstanding physiacal toughness and good resistant to fire.

Physically, silicones are based on silicon, an element derived from quartz. To create this class of synthetic elastomers, pendant organic groups such as methyl, phenyl and vinyl are attached to silicon atoms. The different addition of side chains can achieve significant variations in properties. Silicones have excellent heat, ozone and corona resistance, very well dielectric stability, and resistance to many oils, chemicals, and solvents. And for all elastomers, silicones possess the best flexible property at low temperature. But it also have some weakness like low tensile strength, poor tear and wear resistance.