Degradation of Wood Flour/Poly (Lactic Acid) Composites Reinforced by Coupling Agents and Organo-Montmorillonite in a Compost Test

Abstract

To investigate the degradation properties of wood flour (WF)/poly (lactic acid) (PLA) composites modified with organo-montmorillonite (OMMT) and two types of coupling agents, namely, maleic anhydride grafted polypropylene (MAPP) and silane (g-methacryloxypropyltrimethoxysilane, KH-570), pure PLA, OMMT/PLA, and WF/PLA composites were prepared with the hot-press molding method and tested in a compost test for 6 mo.After compost tests, samples were also characterized with scanning electron microscopy, Fourier transform infrared spectrum, and differential scanning calorimeter for further understanding.The results showed that 1) introducing WF and OMMT accelerated the degradability of PLA (after 5 mo, all composites were completely degraded, whereas the pure PLA control still had 4.78% residue); 2) the two types of coupling agents had opposite effects on degradation of WF/PLA composites (MAPP delayed the degradation process, whereas silane accelerated it); 3) silane and OMMT had a synergic effect on degradability, which was supported by the complete degradation of WF/PLA composites modified with both silane and OMMT in 4 mo; 4) after a 3-mo compost, many cracks or voids occurred on the surface of PLA, and this compost test also resulted in separated WF.T m values of PLA and OMMT/PLA decreased and their crystallinity degrees increased, suggesting faster degradation of PLA with WF and OMMT loading.