Microstructure and thermal stability in metallocene iPP-materials: 1-pentene and 1-hexene copolymers

Two series of propylene based copolymers with 1-pentene and 1-hexene, respectively, have been synthesized via metallocene catalysis up to comonomer contents around 14 mol %. The pyrolysis behavior of these propylene-rich copolymers has been studied and compared with the corresponding thermal response of the referential isotactic polypropylene (iPP) homopolymer. Dynamic TGA analysis at different heating rates has been carried out in order to evaluate kinetic changes, all along the weight loss interval, through either the Friedman's method or a pseudo-first order model. A thorough characterization of chain microstructure has allowed screening the chain features which could determine the existence of an initial stage involving a low value of the apparent activation energy. Namely, oxidation degree, molecular weight and comonomer content have been considered. Changes encountered in the pyrolysis kinetics have been found to be consistent with the expected evolution of chain mobility, as the parameter that seems to rationalize the influence of distinct chain characteristics all together.