Influence of ethylene-propylene-diene terpolymer addition on processing parameters, phase structure and thermal behaviour of polypropylene/low-density polyethylene blends

The influence of blend composition and ethylene-propylene-diene terpolymer (EPDM) content on the processing parameters, phase structure and thermal behaviour of polypropylene (PP) and low-density polyethylene (LDPE) blends was studied. Processing parameters of blends in twin-screw extruder were followed by output (Q), torque (TQ) and back pressure (p), and apparent viscosity as given by TQ/Q and p/Q ratios, while the thermal behaviour was measured using differential scanning calorimetry. Phase structure was investigated using scanning transmission electron microscopy (STEM). The degree of crystallinity ((c)) of PP phase decreased and (c) of LDPE phase increased with higher LDPE content in blends with and without EPDM. STEM micrographs of EPDM compatibilized PP/LDPE blends of compositions 80/20 and 20/80 showed particulate morphology, whereas in the blends of compositions 60/40 and 40/60 the morphology was co-continuous. The EPDM compatibilizer was localized on the interface.