THERMOGRAVIMETRIC STUDIES OF POLY(OXYMETHYLENE-CO-DIMETHYLSILOXANE) COPOLYMERS

Abstract

The thermal stability and kinetic parameters of a series of poly(oxymethylene-co-dimethylsiloxane) copolymers have been studied by thermogravimetry from 303 to 846K under nitrogen flow. The new copolymers, obtained by ring-opening copolymerization of 1,3,5-trioxane and hexamethylcyclotrisiloxane, contain different concentrations of oxymethylene and dimethylsiloxane comonomer units. The results of the thermal studies were compared with data corresponding to pure poly(oxymethylene) and poly(dimethyl-siloxane). The copolymers with low concentration of dimethylsiloxane comonomer units show only one degradation process, but copolymers richer in this co-unit degrade in two stages. Copolymers with an even higher concentration of dimethylsiloxane co-unit have three decomposition processes. The TGA results indicate that the molecular structure of the copolymers correspond to block copolymers and random copolymers bonded to segments formed by both pure poly(oxymethylene) and poly(dimethylsiloxane). The structures depend on the composition of the copolymers. The pre-exponential factors, the reaction orders and the activation energies have been determined from non-isothermal thermogravimetric data.