Polymer Bulletin 49. 297-303 (2002) zyxwvu Po I y m er Bu I I et i n z 0 Springer-Verlag 2002 z Radiation processing of EPDM/PP blends Thermal effect of low dose irradiation Traian Zaharescu zyxwvu (B) , Petru Budrugeac R & D Institute for Electrical Engineering, Advance Research Center, 313 Splaiul Unirii, Bucharest 74204, Romania e-mail: zaharescut@rol.ro, fax: 0040-1-346-7283 Received: 20 February 2002/Revised version: 10 August 20021 Accepted: 9 September 2002 Summary The effect of ionizing radiation on thermal oxidation of ethylene-propylene copolymer/polypropylene (EPDMPP) was evaluated over the range of total gamma doses up to 250 kGy. The influence of irradiation dose on oxidation induction periods was investigated by oxygen uptake and thermal analysis on polymer samples containing various concentrations of components (100/0, 80/20, 40/60, 60/40, 20/80 and 100/0 d w ) . Drastic decrease in oxidation induction time was observed for low doses. The competition between crosslinking and scission has been examined on the basis of radical recombination on post-irradiation time. The influence of specimen formulations on oxidation induction time is discussed regarding to the contribution of antagonistic processes: crosslinking and oxidative degradation. Introduction The interest focused on radiation processing of polymers is found in carrying out several studies on mono and polycomponent systems [ 1-10]. The understanding of radiochemical phenomena requires not only endurance investigations when large irradiation doses are applied; short exposures must be selected for learning different effects of scission and crosslinking. Complex description on the interaction between high energy radiation and polymers can be found elsewhere [ 11,121. The formation of free radicals by several scissions of weaker bonds creates intermediates for subsequent processes namely recombination, disproportionation or oxidation. Conditions under polymeric materials have to be investigated regarding the influence of these reaction rates. It is generally accepted that ethylene-propylene elastomers show significant resistance to the action of ionizing radiation [ 12,131. Their radiochemical behavior is similar to polyethylene. On the opposite site irradiation of polypropylene in air induces oxidation because of great proportion of tertiary carbon atoms. In fact, radiochemical oxidation starts with reaction between free radicals and molecular oxygen that exists or penetrates material by diffusion process. The extension of oxidation depends on the lifetime of radicals, the time of exposure and the temperature of radiolysis. General mechanism of polyolefin oxidation was proposed by Bolland and Gee [ 141 for thermal degradation of these polymers but it is usually adopted for high energy irradiated