Biobased plasticizer and cellulose nanocrystals improve mechanical properties of polylactic acid composites

Abstract

Biopolymers are a fundamental part of contemporary life due to their biodegradable and biocompatible nature. Among different biopolymers, polylactic acid (PLA) with ease of processability, is one of the most commercially available biopolymers used in additive manufacturing. However, the low ductility and impact strength limits its application in commercial plastic products. One of the methods to enhance the ductility of PLA is addition of biobased reinforcing agents and plasticizers. The objective of this research is to use biobased materials for improving the mechanical properties of PLA composites. Cellulose nanocrystals (CNC) and distillers dried grains with solubles (DDGS) were selected as reinforcing agents, polyethylene glycol (PEG) as a plasticizer and maleic anhydride (MA) as a coupling agent. Biocomposites containing distillers DDGS (10%), CNC (0.25–1%), PEG (2%), maleic anhydride (0.25%) and PLA (86.75–87.75%) were manufactured using melt blending. To investigate the effects of CNC, PEG, and MA on PLA composites the morphological, ductile, and mechanical, properties of the composites were examined. Morphological changes were characterized by using optical microscopic images, mechanical properties by differential scanning calorimetry and ductility by tensile testing. The results demonstrate that addition of CNC and PEG to PLA improved its mechanical and ductile properties whereas maleic anhydride helped in dispersion of CNC. The observed improvements were attributed to the increased DDGS-CNC-matrix interactions. Optical microscopy also revealed some non-uniform dispersion of CNC. Overall, the results suggest that addition of CNC, plasticizer and coupling agent can aid in improving the physical, mechanical properties of PLA composites.