Deterioration of polypropylene by radiation

Radiation sterilization is not applied to the medical implement using polypropylene because of the severe deterioration by gamma ray irradiation. It has been reported that the chain reaction due to oxygen and peroxide radical contributes to the process of deterioration. The authors concluded that by the irradiation of electron beam, the sterilization of the surgical sutures made of polypropylene is feasible, and reported on the correlation of the lowering of the tensile strength by irradiation and the radical formed. However, the ESR spectra of the radical formed in the surgical sutures made of polypropylene irradiated with electron beam and gamma ray were different from the wave form of the peroxide radical of polypropylene reported before, accordingly, the identification was necessary. By this research, the above ESR spectra were proved by the anisotropy of g of peroxide radical, and the second radical other than the above peroxide radical was found. The experimental method and the results are reported. The research on the deterioration of polypropylene by radiation must be forwarded by examining both conventional peroxide radical P and ''S'' radical. (Kako, I.)