Low-temperature, graft polymerization of tetrafluoroethylene in a crystalline matrix of polydimethylsiloxane

Abstract

When solutions of tetrafluoroethylene in a dimethylsiloxane rubber are cooled slowly, the latter crystallizes and a considerable proportion of the tetrafluoroethylene (20–30% of the weight of the rubber) becomes adsorbed in the pores of the crystalline matrix, but does not itself form a separate crystalline phase. In the course of heating up of such samples after γ-irradiation ( 60Co) at 77°K, graft polymerization of the tetrafluoroethylene occurs over a wide range of temperatures up to the melting point of the rubber. The graft copolymer, which contains a small proportion of grafted PTFE chains, is soluble in benzene. The IR-spectra of films obtained from the solution, contains bands at 1140–1170 cm −1 and 1245–1255 cm −1, characteristic of PTFE. The heat of melting of the crystalline rubber falls uniformly as the quantity of grafted PTFE increases. This preliminary introduction of tetrafluoroethylene into the pores of the crystalline rubber enables efficient grafting of this monomer to be achieved.