High temperature irradiation effect on fully aromatic polymers

On the fully aromatic engineering plastics, of which all the main chains are composed of aromatic rings, the effect of high dose rate electron beam irradiation which is not accompanied by oxidation and gamma-ray irradiation in pressurized oxygen atmosphere, in which oxidation reaction occurs to the inside of polymers, was examined, and the following results were obtained. The radiation resistance changed strongly depending on their chemical structure. The approximate order of the stability against radiation of the aromatic units composing polymers was imide ring > diphenyl ether-diphenyl ketone > aromatic amide >> bisphenol A > diphenyl sulfone. Also aromatic polymers deteriorated at the dose as low as 1/5 - 1/10 under the condition accompanied by oxidation as compared with the case of irradiation without oxidation. According to the examination of molecular mobility and others, in the case of the irradiation without oxidation, polyimide such as polyether-ether-ketone and kapton caused mainly cross-linking, and in the case of oxidizing irradiation, the severance of main chains occurred. In polysulfone and polyarylate, the deterioration due to the severance of main chains occurred also in the case of irradiation without oxidation. These high performance engineering plastics demonstrate excellent mechanical and electrical characteristics even at high temperature. (K.I.)