Mechanical Property and Molecular Weight Distribution Change of Low Density Polyethylene caused by Gamma-Ray and Electron beam irradiation

摘要

In the research on many kinds of polymer materials done on effect of radiation, it has been reported that physical and chemical changes caused by molecular session, cross-linking reaction, generation of the low molecular weight component and so on, influenced the surface structure, gas permeability, strength of the polymer materials. [1-5] Here, Gamma-ray and electron beam irradiated low density polyethylene (LDPE) films were obtained, and their structural change and mechanical property change were examined. In the electron beam irradiation sample, it was found that the part of the crystal structure collapses in the irradiation initial stage, and then the molecular chain in the amorphous phase seems to generate the recrystallization from the result of the change of heat of fusion. At the same time, the trans vinylidene group, which can be assigned to the chain end structure, on cross-linking reactions caused in radiation exposure seems to progress. In the effect to molecular weight distribution by gamma-ray irradiation, though once the cross-linking reactions occurred by the irradiation, the molecular chain scission progressed afterwards, and, as a result, the decline of the molecular weight of LDPE was observed. As for the electron beam irradiation sample, however, the insoluble component (such as gelation) produced by the cross-linking reactions increased and the depolymerization is not almost observed, indicating that it is quite different from the gamma-ray irradiation samples from the electron beam irradiation ones..