Biodegradation of Modified Polypropylene Films

Abstract

The ability of microbes to attack / degrade certain polymers, viz. polypropylene (PP) and its blends with poly-L-lactic acid (PLLA) with/without compatibilizer, maleic anhydride was investigated in pure shake-flask culture conditions. The mesophilic bacterium Bacillus flexus (MTCC number 2909) and fungus Aspergillus niger (MTCC number 478) utilized PP and its blends with PLLA as the sole carbon and energy source(s) and degraded them. Incubation of the mentioned polymers and polymer blends with Bacillus flexus and Aspergillus niger for 60 days and 30 days respectively at 30°C and 120 rpm, under aerobic conditions, reduced their weights. As the growth of microbes proportionally increased in synthetic media so it was predicted that the microbes were solely dependent on the polymer samples for its carbon source. Firstly, the biodegradation of all the polymer samples was observed in terms of their respective weight loss, which is an established indicator of the degradation. It was observed that PLLA degraded maximum by Bacillus flexus i.e. 8.93% (after 60 days) followed by M-g-PP 90/4, which degraded by 1.08%. Pure polymer sample, PP 100 degraded by 0.78%. The above data showed that blend of PP and PLLA undergo more degradation than PP alone. The biodegradation of the films were attributed to microbial attack, with major changes occurring at the surface of the polymer which was confirmed by scanning electron microscopy (SEM). PLLA degrade maximum by Aspergillus niger i.e. by 0.91% (after 30 days) followed by PP 90, which degraded by 0.85% and no weight loss was noticed in PP 100.