ORIGINAL PAPER Influence of silica and electron beam radiation on the properties of a high vinyl styrene-butadiene-styrene block copolymer Sanjoy Datta & Nikhil K. Singha & Y. K. Bhardwaj & Sunil Sabharwal & Kinsuk Naskar Received: 19 August 2010 / Accepted: 18 October 2010 / Published online: 30 October 2010 # Springer Science+Business Media B.V. 2010 Abstract Radiation crosslinking of polymers has gained importance over conventional crosslinking because the system is fast, pollution free and relatively simple. In high energy electron beam curing, which is one of the radiation curing methods, the material to be cured is bombarded with electrons of specified energy to produce free radials. These radicals unite to give rise to chemical crosslinks. In the process, some unwanted chain scission may also occur. The mechanical properties of such electron beam crosslinked systems can further be improved by the incorporation of nanosilica. In this work, a high vinyl (~50%) S-B-S block copolymer incorporated with varying doses of specific hydrophilic nanosilica was irradiated with electron beam at 25 and 50 kGy. Mechanical properties were studied and com- pared with that of the unirradiated system. The influence of a silane coupling agent was also investigated. Morphological studies were done to understand the dispersion of nanosilica in the polymer matrix. Relatively moderate amounts of nanosilica along with an optimum dose of the coupling agent were found to be effective in improving the properties. Rheological properties were also studied in details to understand the possibility of recycling the polymer. Keywords Thermoplastic elastomer . High vinyl S-B-S . Electron beam radiation . Nanosilica . Silane coupling agent Introduction Electron beam crosslinking of polymers have been reported in various texts and comprehensive literature, and the importance is unanimously accepted in view of the relative ease, faster rates and the simplicity of the process over conventional chemical crosslinking [1, 2]. The application of this technology has been successfully explored by the authors in the crosslinking of a special type of a thermoplastic elastomer of S-B-S block type [3]. In general, electron beam radiation in the range of 20– 100 kGy is an effective means of crosslinking many polymers. The final properties of such electron beam crosslinked polymer depend on the polymer type, the ambience, temperature of crosslinking, presence of other chemicals in the form of additives and of course the magnitude of radiation dose. The principle of electron beam crosslinking is based upon the focusing of high energy electrons generated from an electron accelerator on a polymer matrix with the subsequent formation of free radicals. Coupling of these free radicals gives rise to crosslinking with an increase of the molecular weight of the polymer [4]. These fast moving electrons, along with the generation of radicals, generate ions, and excited molecules in droplets along their paths of travel. Such droplets containing several pairs of ions, radicals and excited molecules are called spurs [4]. Though the main Contract grant sponsors: Board of Research in Nuclear Sciences (BRNS), Department of Atomic Energy (DAE), Mumbai, India. S. Datta : N. K. Singha : K. Naskar (*) Rubber Technology Centre, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India e-mail: knaskar@rtc.iitkgp.ernet.in Y. K. Bhardwaj : S. Sabharwal Bhabha Atomic Research Centre, Mumbai 400 085, India J Polym Res (2011) 18:1185–1196 DOI 10.1007/s10965-010-9522-1