Pergamon 0045-6535(94)00142-1 Chemosphere, Vol. 28, No. 12, pp. 2197-2202, 1994 Copyright © 1994 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0045-6535/94 $7.00+0.00 FORMATION OF POLYCHLOROBIPHENYLS IN SILICONE RUBBER A. Perdih 1. and J. Jan 2 1 Department of Chemistry and Chemical Technology, University of Ljubljana, 61001 Ljubljana, P.O.B. 537, Slovenia 2 Public Health Institute of Slovenia, Trubarjeva 2, 61001 Ljubljana, Slovenia (Received in Germany 31 January 1994; accepted 18 April 1994) ABSTRACT In silicone rubber crosslinked with bis(2,4-dichlorobenzoyl) peroxide (DCBP) as initiator about 0.1% of DCBP is converted into polychlorobiphenyls (PCBs). The PCB content in silicone rubber determined by high resolution gas chromatography (HRGC) after its destruction by HF is around 10 mg/kg. 29 PCB congeners were detected. Instead of the expected PCB-47, lower chlorinated congeners are predominant. Some possible pathways of their origin are presented. KEYWORDS Polychlorobiphenyls, bis(2,4-dichlorobenzoyl) peroxide, silicone rubber. INTRODUCTION During decomposition of bis(2,4-dichlorobcnzoyl) peroxide (DCBP) low yields of 2,2',4,4'- tetrachlorobiphenyl (PCB-47) are obtained (Hutzinger et al., 1974) since a number of chlorinated organic compounds are formed, among them polychloro -benzenes (CBz) and -biphenyls (PCBs) (Jan and Perdih, 1990). Menough (1985) proposed the formation of m-dichlorobenzene and 2,2',4,4'-tetrachlorobiphenyl during crosslinking of silicone rubber by DCBP, whereas van Drumpt (1990) studied the formation of PCB from DCBP in pentadecane to approximate the situation in silicone rubber, and detected several tetrachloro isomers. In this contribution the PCB congeners formed during crosslinking of silicone rubber are reported and the formation of different congeners is elucidated. 2197