Modification, degradation and stabilization of polymers in view of the classification of radiation spurs

Classification of spurs according to their size dominated early developments of aqueous radiation chemistry and still applies to polymers dissolved in water. The energy of ionizing radiation is absorbed proportionally to the participation of electrons in the system and therefore in diluted aqueous solutions in polymer is attacked by products of radiolysis of water and the direct interaction of radiation with polymer is negligible. Pure polymers also absorb the ionizing radiation energy heterogeneously with the resulting variety of spur sizes. A full theoretical approach, already difficult and not fully understood in the case of water, is practically impossible for polymers at the time being, but there are sufficient experimental facts, showing that, even with low LET radiation, there is a full spectrum from single-ionization to multi-ionization spurs. The paper promotes the idea that single-ionization spurs do not cause the chain scission, but are responsible for energy transfer, protection effect (in aliphatic-aromatic copolymers and blends) and grafting. Large spurs with their high concentration of energy cause chain-scission and low MW debris. Depending on the type of polymer, all sizes of spurs can contribute to radiation-induced crosslinking. (C) 2001 Elsevier Science Ltd. All rights reserved.