Assessment on radiochemical recycling of butyl rubber T. Zaharescu * , C. Cazac, S. Jipa, R. Setnescu R&D Institute for Electrical Engineering, ICPE SA, Laboratory 68, 313 Splaiul Unirii, P.O. Box 104, Bucharest 74204, Romania Abstract The behavior of butyl rubber samples subjected to accelerated electron beams or c-rays was studied in order to characterize its availability to radiation processing. Changes in some main properties such as average weight, molecular weight, gel content, Mooney viscosity, unsaturation level and degradation index were determined at various doses. Vulcanized butyl rubber starts signi®cant radiodegradation at about 45 kGy. An advanced irradiation of IIR will decrease sharply the molecular weight of vulcanizates providing suitable plasticization matter for other kinds of syn- thetic rubbers. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Butyl rubber; Irradiation 1. Introduction Radiation eects are always related to the split of weak bonds and the subsequent reactions in- volving free radicals [1]. The main processes that occur in various irradiated polymers are cross- linking and degradation. The characterization of radiation modi®cation of polymer materials has increased because of the need of enlarging the application areas, the assessment of radiation sta- bility or, more recent, recycling purposes. The de- scription of elementary reactions occurring in irradiated polymers can be found elsewhere [2,3]. Speci®c consequences of high energy exposure are described in detail in several studies for example [4±6]). The routes on which various intermediates are depleted in¯uence the stability of irradiated poly- mers. Some polymers like polyethylene are cros- slinkable because free radicals generated during c or accelerated electron irradiation make up a three-dimensional structure by recombination [7]. Other macromolecular materials like polypropy- lene irradiated in air [8] or the majority of rubbers [9,10] are degraded either by radiation oxidation or by removal of some volatile products. Industrial applications of radiation eects in polymers cover many economical branches. Man- ufacture of various wire insulators, shrinkable tubes, surface protections or foams by radio- chemical procedures gain an important position in the ecological activities. Recently, the reprocessing or recycling of polymers under radiation has been continuously extended because of their low cost, Nuclear Instruments and Methods in Physics Research B 185 2001) 360±364 www.elsevier.com/locate/nimb * Corresponding author: Tel.: +40-1322-2813; fax: +40-1321- 3769. E-mail addresses: traian@gw-chimie.math.unibuc.ro, traian_z@hotmail.com T. Zaharescu). 0168-583X/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0168-583X01)00813-8