Enzymatic degradation of coconut shell powder–reinforced polylactic acid biocomposites

Abstract

This work examined the effects of filler content and chemical treatment on the biodegradation of poly(lactic acid) (PLA)/coconut shell (CS) biocomposites in a diastase enzyme-containing buffer medium. CS was treated with two distinct chemical treatments: maleic acid and silanation with 3-aminopropyltriethoxysilane (3-APE). The CS was incorporated into PLA composites and their biodegradation patterns were studied. Both of the treated PLA/CS biocomposites exhibited lower biodegradation rates than the untreated biocomposites due to their enhanced interfacial adhesion, which reduced the area exposed to enzyme hydrolysis. Scanning electron micrographs taken after 30 days of biodegradation displayed surface roughening on both of the treated biocomposites, with fewer voids compared to the untreated biocomposites. The differential scanning calorimetry indicated that the glass transition temperature and melting temperature values of the treated biocomposites increased but that crystallinity declined. The crystallization temperature peak apparently disappeared due to the polymer chain alignment and rearrangement of the shorter PLA chains caused by the degradation. Fourier transform infrared analysis revealed the structural changes in the biocomposites after biodegradation, indicating the presence of soluble lactic acid as was confirmed by ultraviolet–visible spectroscopy analysis.