Morphological, structural, thermal and degradation properties of polylactic acid-waxy maize starch nanocrystals based nanocomposites prepared by melt processing

Abstract

Currently used petroleum-based polymers have adversely affected the environment in various ways, mainly due to their non-biodegradability. This undesirable aspect of commercial polymers led to increased interest in the research area of biodegradable polymer nanocomposites. Polylactic acid (PLA) based nanocomposites, with three different loadings of waxy maize starch nanocrystals (WSNC) as nanofiller (1, 3 and 5 wt%), were melt-blended in a Haake Rheomix. The morphological, structural, thermal and abiotic degradation characteristics of the prepared PLA-WSNC nanocomposites were studied to determine the effects of adding WSNC at different loadings in PLA. The results indicated that WSNC were dispersed uniformly at lower loadings (0-3 wt%) and agglomerated at higher loadings (5 wt%) within the PLA matrix. All PLA-WSNC nanocomposites were found to be stable over the processing temperature range of 25-220 ºC. In addition, there was no considerable change in the glass transition temperature and the melting point of the nanocomposites. Though, the cold crystallization temperature was reduced with the increase of WSNC loadings. The abiotic degradation studies, used as an initial screening tool, indicated that WSNC can accelerate the degradation process of PLA. As a result, the degradation rate was improved for all the PLA-WSNC nanocomposites. The PLA-WSNC-3 wt% was found to be the optimum concentration to enhance the crystallinity and morphological property of PLA, and beyond that the properties were affected by agglomeration.