Preparation and Properties of LLDPE/PMVS Blends

Abstract

Reactive blending has been carried out by the melt mixing of linear low density polyethylene (LLDPE) and silicone rubber containing vinyl group (PMVS) to obtain grafted and crosslinked blends. Two methods involving the use of free radicals generated from (a) thermomechanical shear and (b) peroxide decomposition were used to prepare the LLDPE/PMVS blends. The occurrence of grafting and crosslinking of the PMVS molecular chains was deduced by considering the mixing torque, solvent extraction data and evidence from the Fourier transform infrared spectra (FTIR), as well as differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experimental results indicated that reactive blending significantly improved the interfacial adhesion between the two phases and that peroxide decomposition had a higher initiation efficiency in respect of grafting and crosslinking than thermomechanical shear. Thermogravimetric analysis (TGA) showed that reactive blending with PMVS improved the thermal stability of LLDPE. Dynamic rheological behaviour and melt flow rate (MFR) results suggested that grafting and crosslinking between the two components increased the viscoelasticity of the blends and the addition of PMVS improved the processability of the LLDPE. Crosslinking by peroxides gave a higher tensile strength than thermomechanical shear but a lower elongation at break. The limiting oxygen index (LOI) test indicated that the flame retardancy of the LLDPE/PMVS blend increased with increasing amounts of PMVS.