Elastomers protective film mechanism

Involvement of the Ozonized Rubber Moieties in Antiozonant Mechanism. The rubber chain relinking theory (30) is consistent in part with the self-healing film formation theory (37) a reaction between an antiozonant or some of its transformation products and ozonized elastomer is considered. Either scission of ozonized rubber is prevented in this way or severed parts of the rubber chain are recombined (i.e., relinked). A "self-healing" film resistant to ozonation is formed on the rubber surface. Such a film formed by the contribution of nonvolatile and flexible fragments of the rubber matrix should be more persistent than any film suggested in the protective film theory. 

The type and extent of the processing and the protection needed depend partly on the type of the plastic and partly on the intended application. Normally, plastics are classified according to their mechanical and thermal behavior as thermoplasts, elastomers, thermosets (duroplasts), and fibers (see also Section 11.1). According to the application, further distinctions are made among construction materials, insulating materials, adhesives, floor sealants, paints, films, soundproofiing media, etc. 

Other commercial fluoropolymers (all made by free-radical mechanisms) include polychlorotrifluoroethylene (Kel-F), which is similar to PTFE but which can be moulded at temperatures 300 °C. Polyvinylidene difluoride (PVDF) is a thermoplastic (T 160°C) and films of this material show piezoelectric behaviour. When copolymerized with hexafluropropene a very chemically resistant elastomer is obtained (Viton). Polyvinylfluoride (PVF) is another highly crystalline polymer (T 197°C) which is used for high-performance protective coatings. 

Polyesters in wire and cable applications include Hytrel (Du Pont), a thermoplastic polyester elastomer for the offshore industry Kapton (Du Pont), a polyimide film offering weight saving and chemical resistance and Mylar (Du Pont), used in primary insulation, shield isolation, chemical barrier, and mechanical protection. 

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