Cure kinetics and mechanical properties of compatibilized blends of low density polyethylene and poly dimethyl siloxane rubber

The cure kinetics of the blends of Low density polyethylene (LDPE) and Polydimethyl siloxane rubber (PDMS) (50 : 50w/w) with different proportion of ethylene methyl acrylate (EMA) copolymer as an in situ compatibilizer, is studied by differential scanning calorimetry (DSC) and rheometry, using dicumyl peroxide (DCP) as the curing agent. EMA reacts with PDMS to form EMA grafted PDMS (EMA-g-PDMS) which acts as the compatibilizer for the blend systems. The grafting of EMA is confirmed from FT-IR studies. The different kinetic parameters such as reaction enthalpy (Delta H), activation energy (Delta E), frequency factor (Z), and order (n) of the curing reaction are evaluated from the DSC trace. The reaction enthalpy decreases with increasing proportion of EMA in the blends whereas, the activation energy for the curing reaction shows the reverse trend. The order of the curing reaction is found to be of first order. The mechanical properties (e.g., tensile strength, modulus, energy to rupture, etc.) are found to increase with increasing proportion of EMA in the blends and becomes the maximum at 6wt% of EMA, which is taken as the optimum level of EMA for the blend systems. The improvement of mechanical properties of the blend vulcanizates with the EMA content in the blend is due to better dispersion of the blend constituents in presence of the compatibilizer as confirmed from scanning electron microscopy.