Effect of Titanium Dioxide and Silicon Dioxide on the Thermal Stability of Isotactic Polypropylene Deformed via Solvent Crazing Mechanismстатья
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Дата последнего поиска статьи во внешних источниках: 2 апреля 2015 г.
Аннотация:The effect of a finely divided structure created via the mechanism of delocalized crazing on the
processes of thermooxidative degradation of isotactic polypropylene has been studied. It has been shown
that the thermal stability of porous films is reduced at relatively low temperatures (up to 155°C) and they become brittle. In contrast, their degradation rate at temperatures above 400°C is two times below that for the original, nonporous films because of the formation of crosslinked network structures and carbonization. The formation of titania and silica nanoparticles via hydrolytic decomposition of the respective alkoxides directly in the pore space of the polypropylene matrix substantially alters its thermal stability, depending on the precursor concentration, the extent of hydrolysis, and the composite structure. The greatest increases in the masslossonset temperature and the temperature of the maximum massloss rate (by 80–100°C) have been observed for the composites with 40 wt % titanium dioxide. It has been assumed that the enhancement of thermal stability is due to the significant concentration of the products of incomplete hydrolysis of titanium alkoxy derivatives. The silica particles, in contrast, exert a signification influence on the thermooxidative degradation processes in polypropylene at their low concentration (up to 5 wt %), a result that is associated with the structural features of such composites.