Photoradical ageing of polymers

摘要

New data referring to quantum efficiency of electronically excited macroradicals and radical anion reactions in various carbon- and heterochain polymers at temperatures below their glass transition or melting points are presented and discussed, The data on the mechanism of the photochemical reactions of peroxy radicals, the effect of various factors (photon energy, free volume, degree of crystallinity) on the direction and efficiency of reactions of electronically excited macroradicals are considered. The important role of photochemical chain reactions in photoageing is demonstrated. It is found that by varying photon energy, temperature, photolysis time and by taking advantage of the competition between thermal and photochemical reactions, it is possible to change the functional composition and molecular mass distribution of polymers in the desired direction.