Evaluation and Enhancement of Polylactic Acid Biodegradability in Soil by Blending with Chitosan

This study highlights the soil burial degradation of polylactic acid/chitosan (PLA/Cs) biocomposites prepared by the melt compounding technique. The effect of various Cs loadings (2.5, 5, 7.5, 10 parts per hundred parts of polymer (php)) and soil burial periods (0, 2, 6, 12 months) on visual observation, weight loss, changes in functional groups, as well as tensile, thermal, and morphological properties were analyzed. The PLA/Cs biocomposites became brittle and showed more fragmentation with increasing Cs content and buried time. The result correlates with a remarkable increase in weight loss percentage of about ~ 192%, with Cs addition from 2.5 to 10 php at the end of soil degradation. Besides, a decrement in peak intensity at 1751 cm−1 and 1087 − 1027 cm−1 after 12 months signifies the breakdown of PLA ester bonds due to the hydrolytic degradation. This correlates to a significant drop of 60% and 55% in tensile strength and elongation at break, respectively, in the 2.5 php sample, whilst further Cs addition resulted in the broken of the biocomposites at the end of the soil degradation. Yet, no significant difference was observed in the tensile modulus. A consistent stiffness in the biocomposite suggests the degradation occurs in the amorphous region and leaves the crystalline part. This is proven by the 70% increment in crystallinity degree in all samples after 12 months of soil burial. Moreover, surface morphology showed numerous and extended crack formations. It proposes a notable deterioration effect of the biocomposite due to biodegradation. The hydrophilicity of Cs enhances water-polymer interaction, thereby accelerating the biodegradation of polymer components. Therefore, Cs could be a good candidate for facilitating PLA biodegradation in the natural soil environment.