Physico-mechanical characterization and biodegradability behavior of polypropylene/poly(L-lactide) polymer blends

Partially biodegradable polymer films from the blends of polypropylene (PP) and poly(L-lactide) (PLLA) were prepared in an internal mixer by melt blending technique, with and without compatibilizer, maleic anhydride grafted polypropylene (MAPP), followed by compression molding. With regard to tensile properties, 80/20 (PP/ PLLA) and 80/20/6 (PP/PLLA/MAPP) were found as the optimum blends with best combination of the ingredients. Therefore, the blend samples, namely, PP80 (80% PP+20% PLLA) and PP80C6 (80% PP+20% PLLA+6 phr MAPP) were selected as 'optimized' blends and further characterized for their physical, chemical, morphological, and thermal properties. X-ray diffraction studies showed that neat PP and PP80C6 had the same crystallite size indicating compatibility between PP and PLLA due to MAPP. Fourier transform infrared spectroscopy and scanning electron microsopy investigations revealed that the two polymers were completely immiscible in absence of the compatibilizer. Bacterial biodegradation of the samples was performed by exposure to Pseudomonas stutzeri for 60 days and measured in terms of weight loss, optical density, and thermal stability of the samples before and after degradation. The results showed that 80/20 (PP/PLLA) blends undergo considerable degradation. Reduction in thermal stability of the film samples was also observed through thermogravimetric analysis, which was useful in accelerating their biodegradation.