Electron beam processing of rubbers and their composites

Abstract

Abstract Electron beam (EB) processing of pristine and filled polymeric materials is considered as one of the most viable techniques in the development of three-dimensional (3D) network structures of polymeric or composite systems with improved physical and chemical properties. The grafting, or the crosslinking process induced by the merging of the macro free radicals generated during the electron beam modification without the aid of any chemical agent or heat, is responsible for the formation of the 3D networks in polymeric systems. Owing to its distinct advantages such as fast, clean and precise, electron beam (EB) radiation technology takes up a vital role in the crosslinking of polymeric compounds. However, during the course of electron beam treatment of polymers, two processes viz., crosslinking and chain scission take place simultaneously, depending on the level of radiation dose used for the processing. The present paper reviews the role of irradiation dose in the presence and absence of radiation sensitizer on the crosslinking and structure formation in a wide variety of soft matrices such as elastomers, latexes, thermoplastic elastomers and their respective filled systems. Notable improvements in mechanical and dynamic mechanical properties, thermal stability, processing characteristics, etc., of the EB processed elastomers and their composites are discussed elaborately in the paper. Specially, the property improvements observed in the EB processed pristine and filled rubbers in comparison to the conventional crosslinking technology are critically reviewed. The level of radiation dose inducing crosslinking in both pristine and filled rubbers, determined by calculating crosslink to scission ratio on the basis of Charlesby–Pinner equation is also discussed in the paper. Finally, the application aspects of electron beam curing technology with special emphasis to cable and sealing industries as developed by one of the authors are highlighted in the paper.