Electron-beam irradiation of poly(vinyl chloride)/epoxidized natural rubber blends in presence of trimethylolpropane triacrylate

Electron-beam initiated crosslinking of poly(vinyl chloride)/epoxidized nat ural rubber blends, which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20-200 kGy) and concent rations of TMPTA (1-5 phr). The gel content increased with the irradiation dose and the TMPTA level, although the increase was marginal at higher dose s and higher TMPTA levels. Blends containing 3-4 phr TMPTA achieved optimum crosslinking, which in effect caused the maximum tensile strength (TS) at a dose of 70 kGy. A further addition of TMPTA caused a decline in the TS ab ove 40 kGy that was due to embrittlement, which is a consequence of excessi ve crosslinking and the breakdown of the network structure. The possible fo rmation of a more open network as a result of the breakdown of the network structure was further confirmed by the modulus results. Dynamic mechanical analysis (tan delta curve) and scanning electron microscopy studies on samp les irradiated at 0 and 200 kGy were undertaken in order to gain further ev idence on the irradiation-induced crosslinking. The plasticizing effect of TMPTA prior to irradiation and the formation of microgels upon irradiation were also discussed. (C) 2001 John Wiley & Sons, Inc.