Structre-Property Relationship of Linear Low Density Polyethylene and Poly Dimethyl Siloxane Rubber Blends on Electron Beam Irradiation

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane (PDMS) rubber at various doses of radiation ranging from 50 to 300 kGy have been studied. The radiation exposed sheets were analyzed for its gel content, dynamic mechanical properties, melting behaviour, thermal stability, dielectric properties and phase morphology. It is observed that the gel fraction increases with increase in the radiation dose as well as the PDMS content in the blends. Dynamic mechanical property after radiation exhibits appreciable increase in glass transition temperature (T_g) of the blends as expected where as the mechanical properties such as tensile strength improved marginally on radiation exposure. This observation agrees well with the relative increase in storage modulus (E^I’). Degree of crystallinity and melting behaviour of the blends remain unchanged up to a radiation dose of 100 kGy. However, beyond this dose the crystallinity and melting temperature decreases, expected to be due to chain scission. Thermal stability increases with increase in the proportion of PDMS rubber in the blends prior to irradiation as well as after electron beam irradiation upto a dose of 100 kGy. The surface topography of the LLDPE-PDMS blends exhibit a two phase morphology before electron beam irradiation where as after electron beam irradiation, it shows a single phase morphology implying that inter as well as intromolecular crosslinks are formed in the blend system, after irradiation leading to a stable single phase morphology.