Electrical insulators esp. cable coatings comprise a polythene homo- or copolymer cross-linked with a peroxide e.g. di-tert-butyl-peroxy-diisopropylbenzene, and contg. a phenolic anti-ageing agent e.g. 4,4'-thio-bis-(3-methyl-6-tert-butylphenol), in combination with a surface-treated silicate filler, e.g. kaolin or talc coated with a silane e.g. vinyltris-(ethoxymethoxy)silane or a long-chain carboxylic acid e.g. stearic. The presence of the surface-treated filler enables smaller amts of stabiliser to be used thereby improving the dielectric characteristics of the insulator, without interfering with the crosslinking process.
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