Immobilization of antioxidant on nanosilica and the aging resistance behavior in polypropylene

Nanosilica was firstly reacted with the reactive antioxidant, methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (AO), via transesterification, to form a nanosilica-immobilized antioxidant, AO-silica. And then it was incorporated into polypropylene (PP) by melt compounding. Fourier transform infrared spectroscopy combined with the other characterization methods elucidated that the reactive antioxidant was chemically immobilized onto the nanosilica surface. SEM observation showed that the nanosilica-immobilized antioxidant was homogeneously dispersed into the matrix of PP. It has been reported that the antioxidative efficiency of AO-silica was superior to the corresponding low molecular counterpart (AO), based on the measurement of the oxidation induction time (OIT) of the PP/AO-silica and the PP/AO compounds containing equivalent antioxidant component. By paying attention to the changes of carbonyl absorption at different UV exposure times, it was observed that the UV aging-resistance ability of PP/nanosilica-immobilized antioxidant was much higher than that of PP/neat nanosilica compound during the long-time accelerated photo aging.