Application of target theory for the radiation degradation of mechanical properties of polymer materials

摘要

Radiation resistance of polymer materials is determined in terms of the change in mechanical properties, such as elongation or flexural strength at break [1], To study change in molecular weight, radical formation and gas evolution are important subjects in the fundamental radiation chemistry of polymers, and attempts have been made to relate them to radiation resistance [2]. However, the behaviour of mechanical properties with dose is very complicated; that is, the properties sometimes remain unchanged up to some dose, while changing drastically with a further dose. On the other hand, radical and gas yield, in general, increase linearly with dose. This is obviously because the dynamics determining the mechanical properties are not simple. A similar sigmoid-like behaviour with dose can also be observed in radiation biology to describe the survival probability of cells, viruses etc., after exposure to radiation. Radiation biologists explain the behaviour by postulating that radiation activates a sensitive portion of the cell after a certain number of shots [3]. This idea is called target theory. The survival fraction is well explained by the following formula.