COLOR FORMATION IN IRRADIATED POLYMERS

Discoloration is a problem in the radiation processing of polymers (su ch as radiation sterilization), and also in emerging applications in w hich optical-property materials are used in radiation environments (su ch as scintillation detectors). We have completed a survey of 17 diffe rent types of optical polymers, in which it is found that these materi als form both permanent and annealable color centers, but in very diff erent magnitudes and ratios. Optical absorption spectra of irradiated polymers both immediately after irradiation and following different ti me periods of annealing are provided. Also provided are tables showing rank ordering of the relative resistance of different polymer types t o induced discoloration. It is found that the extent of radiation-indu ced discoloration of polymers has little or no dependence on whether t he macromolecule is aromatic or aliphatic, and shows no correlation wi th the relative extent of radiation-induced mechanical property change . Examples of the influence of stabilizer additives on the extent of d iscoloration are discussed.