TPE Replaces Liquid Silicone In Electrical Insulators.

Since the 1970s, insulators used in power distribution have evolved from porcelain to cast epoxy to liquid silicone rubber (LSR) and now to thermoplastic elastomer. In the last three years, GLP HiTech Power Products Inc. in St-Jean-sur-Richelieu, Que., has been injection molding a new type of dead-end composite insulator with an overmolding of Dytron XL TPE from Applied Elastomer Systems, L.P. (AES), Akron, Ohio. GLP molds the insulators in lengths from 13.1 to 22.6 in. They weigh 1.7 to 2.3 lb.

Dytron XL is a non-halogenated, flame-retardant compound with a polypropylene matrix containing dynamically vulcanized rubber and alumina trihydrate. It was developed specifically for wire, cable, and other electrical applications. Until recently, it was available mainly in Europe. AES is now beginning to market it actively in North America, where it is finding new uses such as molded insulators for electric rail systems.

This TPE beat LSR in laboratory tests of dielectric strength, which registered 12.59 kV/mm for LSR and 21.96 kV/mm for Dytron XL. The TPE also passed the stringent FVO flammability test, as well as the 1994 and 1996 tracking-wheel tests, two severe measures of insulator performance in pollution and salt-spray conditions.