EFFECT OF PHOTODEGRADATION ON THE BETA-RELAXATION IN POLY(METHYLMETHACRYLATE)

The effect of photodegradation using UV radiation on the beta-relaxati on in poly(methylmethacrylate), PMMA, was investigated dielectrically within the temperature range 60-90 degrees C and a 20-10(5) Hz frequen cy band. It is shown that the irradiated samples exhibit a beta-relaxa tion process similar to that of unirradiated PMMA but with broader dis tribution of the relaxation times. Increasing the time of UV exposure increases the magnitude of the relaxation and displaces the peak towar d lower temperature. The apparent activation energy decreases with irr adiation. It is suggested that these observations can be interpreted i n terms of the chain scissioning of the polymer chains without extensi ve depolymerization. (C) 1996 Elsevier Science Limited