Rheology, mechanical properties and thermal degradation kinetics of polypropylene (PP) and polylactic acid (PLA) blends

The blending of immiscible polymers and their compatibilization leads to materials with tailor-made properties suitable for wide range of applications. Polypropylene (PP) and polylactic acid (PLA) were blended in different weight ratios and the optimized blend was compatibilized with maleic anhydride grafted PP (MA-g-PP) in varying amounts from 0 to 5 wt%. Rheological studies performed using a capillary rheometer showed the pseudo plastic behavior of the blends and from the shear viscosity data, it was observed that 3 wt% of the compatibilizer effectively compatibilized the selected blend. Mechanical properties further confirmed this finding. Thermogravimetric analysis revealed a two-stage degradation mechanism for the blends, corresponding to each component in the blend system. The apparent activation energy (E a ) values for the thermal degradation were calculated using Kissinger method, Horowitz and Metzger method, Kissinger-Akahira-Sunose equation, Friedman model and Ozawa-Flynn and Wall method. Coats-Redfern method was used to elucidate the mechanism of thermal degradation of the chosen blend system. The E-a values for PLA component of the blend increased with increase in compatibilizer addition up to 3 wt% and then decreased, whereas, it decreased for PP fraction up to a compatibilizer level of 3 wt% and then increased.