Thermal analysis study on the degradation of the solid-state chlorinated poly(ethylene)

摘要

Both the thermal and thermooxidative degradation of the product which was prepared by the solid-state chlorination of poly- (ethylene) and contained from 1.27 to 56.09 chlorine bound chemically were studied by using the combined thermal analysis method. The degradation was found to occur in two stages, whose temperature intervals depended on the chlorine content. The corresponding temperatures ranged from 210 to 435℃ for the first stage and from 370 to 590℃ for the second one. A number of thermal and some kinetic parameters characterizing the degradation of the solid-state chlorinated poly(ethylene) (CPE) were determined such as temperature of 50 decomposition (T_50), maximum temperature of decomposition (T_max), coke residue at 550℃ (CR_550℃), the apparent energy of activation for the dehydrochlorination process (Ed), the effective maximum rate of mass- release (R_max), etc. Some parameters such as the apparent energy of activation E_d and coke residue CR_550℃ were found to increase with the higher chlorine content in the macromolecules. By employing the basic Avrami-Erofeev equation, both the kinetic expo- nent and rate constants for dehydrochlorination of “pure” CPE and, also, for CPE blended with stearic acid and dicumylperoxide, respectively, were determined. Dehydrochlorination was promoted in the presence of these additives at 150℃ in an inert medium. It was controlled by the relatively slow diffusion process and the corresponding rate of dehydrochlorination changed during the reaction course. The apparent rate constants of dehydrochlorination were found t