Thermal degradation studies of poly(urethane–siloxane) thermosets based on co-poly(dimethyl)(methyl, hydroxypolyoxyethylenepropyl) siloxane

Abstract

• The thermal decomposition of the poly(urethane–siloxane) thermosets based on siloxane was investigated. • The TGA–FTIR of evolved gases during degradation were performed. • The thermal degradation kinetic parameters were determined. • The possible degradation model f(α) was proposed. A series of crosslinked hybrid poly(urethane–siloxane) networks based on comb-like structure co-poly(dimethyl)(methyl, hydroxypolyoxyethylenepropyl) siloxane cured with aliphatic diicocyanates hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 4,4′-methylenebis(cyclohexyl isocyanate) (H 12 MDI), were obtained. The samples have been submitted to thermal stability investigations at non-isothermal conditions in nitrogen and air. The thermal degradation behavior was investigated by evolved gas analysis, using coupled TG–FTIR technique. The kinetic parameters of the degradation process were determined both by isoconversional methods of Friedman and Ozawa–Flynn–Wall as well as by model fitting multivariate non-linear regression method. It was observed that the thermal stability of the poly(urethane–siloxane) thermosets depends on employed diisocyanate. The best fit of the f ( α ) function with the experimental data was found for two-step degradation mechanism. Successive stages of thermal decomposition occurred by diffusion and by the expanded Prout–Tompkins model, respectively.