Influence of organic and inorganic fillers on the photoaging behavior of polyolefins

Abstract

The use of fillers has become a common approach of improving the performance of polymer composites. In this study, the photooxidation activity and radiation absorption phenomena of silica, cellulose and carbon black, which differ in morphology (shape, particle size), structure, coloration and degree of dispersion, were investigated. Ethylene-norbornene copolymer was selected as the polymer matrix because it is an ideal transparent medium for studying aging processes. Samples were subjected to accelerated UV (340 nm) and solar (315–1400 nm) aging tests in special chambers for 300, 500, 700 and 900 h. The obtained results demonstrated that composite filled with carbon black exhibited the highest photostability and retained its functional properties; after 900 h of exposure to radiation, its aging factor value was still close to 1. It was observed that carbon black limits the penetration of radiation by absorbing it. Moreover, its role against photooxidation can be considered in terms of antioxidant activity, probably through the catalytic decomposition of peroxides and reaction with free radicals. Completely different aging behavior was noted for composites containing silica and cellulose, which lost their performance properties. This could be related to their weaker dispersion in the polymer matrix and greater susceptibility to the oxidation process, which was confirmed by FTIR analysis.