Effect of electron beam irradiation on the structure-property relationship of linear low-density polyethylene and polydimethylsiloxane rubber blends

摘要

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and polydimethylsiloxane (PDMS) rubber at various doses of radiation ranging from 50-300 kGy have been studied. The irradiated sheets were analyzed for its gel content, dynamic mechanical properties, melting behaviour, thermal stability and phase morphology. It is observed that the gel fraction increases with increase in the radiation dose as well as the PDMS rubber content in the blends. Dynamic mechanical analysis (DMA) after irradiation exhibits appreciable increase in glass transition temperature (T_g) of the blends as expected where as the mechanical properties such as tensile strength improves marginally on radiation exposure. This observation agrees well with the relative increase in storage modulus (E"). Degree of crystallinity and melting behaviour of the blends remain unchanged up to a radiation to dose of 100 kGy. However, beyond this dose the crystallinity and thus the melting temperature decreases, supposed to be due to chain scission. X-ray diffraction analysis (XRD) study gives a clear indication about the structure of these binary blends before and after electron beam irradiation. Thermal stability increases with increase in the proportion of PDMS rubber in the blends prior to irradiation as well as upon electron beam irradiation up to a dose of 100 kGy. The surface topography of these LLDPE-PDMS blends exhibit a two phase morphology before electron beam irradiation where as upon electron beam irradiation it exhibits a single phase morphology interpreted as due to inter and intramolecular crosslink formation as well as interfacial crosslink formation in the binary blends.