Influence of Electron Beam Radiation on Mechanical and Thermal Properties of Styrene-Butadiene-Styrene Block Copolymer

Electron beam crosslinking of elastomers is a special type of crosslinking technique that has gained importance over conventional chemical crosslinking method, because the former process is fast, pollution free, and simple. The technique involves the impingement of high-energy electrons generated from electron accelerators and the subsequent production of free radicals on target elastomers. These radicals result in crosslinking of elastomers via radical-radical coupling. In the process, some chain scission may also take place. In this work, a high-vinyl (similar to 50%) styrene-butadiene-styrene (S-B-S) block copolymer was used as the base polymer. An attempt was made to see the effect of electron beam radiation on the mechanical and thermal properties of the block copolymer. Radiation doses were varied from 25 to 300 kGy. Mechanical properties like tensile strength, elongation at break, modulus at different elongations, hardness, tear strength, crosslink density, and crosslink to chain scission of the irradiated samples were studied and compared with those of unirradiated ones. In this S-B-S block copolymer, a relatively low-radiation dose was found effective in improving the level of mechanical properties. Differential scanning calorimeter and dynamic mechanical analyzer were used to study the thermal characteristics of the irradiated polymer. Influence of a stabilizer at different concentrations on the properties of S-B-S at varied radiation doses were also focused on. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2573-2581, 2010