Vulcanised fluorocarbon

As has been shown in Chapter 6, in addition to crumb from waste tyres, it is possible to commercially source crumb from a number of other rubber types, e.g., fluorocarbon rubber. Shell [30] has carried out a study whereby micropowder from vulcanised fluorocarbon, silicone and nitrile wire insulation rubber has been put back into wire compounds using an open mill. The loadings chosen were those that maximised the performance and economic efficiency of the formulations. 

A number of synthetic, noncrystalline fluorocarbon copolymers exhibit elastomeric properties when vulcanised. Such elastomers are of commercial interest because they have unusual combinations of properties e.g., high melting point, high thermal stability, insolubility, low coefficient of friction and flexibility at low temperatures. They are designed for demanding service applications in hostile environments characterised by broad temperature ranges and contact with chemicals, oils or fuels. 

The silicone rubbers show not only very good heat resistance, like the fluorocarbons, but also very good properties at low temperatures. The uses of these materials are well established where operation over a wide service temperature range is required. In recent years, however, these materials have been facing competition, for some of the less stringent applications, from some of the less expensive speciality materials. These include the acrylic rubbers and the ethylene-acrylate rubbers already mentioned. On the other hand there has become available a special group of silicone materials which may be vulcanised at room temperature, the so-called RTV rubbers. 

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