Properties and biodegradation modeling of abiotically treated modified-cobalt stearate filled polypropylene films

The present work studies the effects of abiotic pretreatment on the properties and biodegradability of the modified cobalt stearate pro-degradant filled polypropylene films, and on the eco-toxicity of their biodegraded products. Before abiotic pretreatment, their processability was confirmed by rheological studies. After abiotic pretreatment, FTIR revealed their carbonyl index increased on increasing the pro-degradant loading. Their GPC results showed significant decrease in molecular weight, thus indicating chain scission and intermediate formation. Their thermal stability also reduced as demonstrated by TGA. Their DSC and XRD analyses showed decreased crystallinity thereby indicating increased biodegradability. Their biodegradation was measured following ASTM D 5338, which showed a significant increase with abiotic pretreatment and the same was substantiated by GPC. The biodegradation kinetics followed Komilis model which showed that the degradation rate reached a maximum of 0.407–0.730% per day at 15–25th day. Readily hydrolysable carbon and its hydrolysis rate constant substantially enhanced with modified pro-degradant content. High readily hydrolyzable carbon rate constant caused the occurrence of a prominent growth phase. SEM also confirmed that the surface morphology of each film became increasingly rougher subsequent to both abiotic and biotic treatments, and with increasing pro-degradant loading. The eco-toxicity tests confirmed the nontoxicity of biodegraded products. The work thus illustrated that the films can have useful packaging applications. Graphical abstract