Properties of poly(lactic acid)/cellulose nanofiber biocomposites: Effect of polymeric plasticizers

Biodegradable composites from renewable resources have been of much interest in many industries. This work aims to develop a poly(lactic acid) (PLA)-based composite with a good balance of stiffness and impact strength by combined utilization of cellulose nanofiber (CNF) and polymeric plasticizer. The composites were prepared by a melt-compounding process. CNF, having diameters of approximately 10 nm and lengths of several microns, was extracted from wood sawdust and used without any surface modification. The effects of polymeric plasticizer selection on the thermal properties and mechanical performance of PLA and PLA/CNF composites were explored. Poly(butylene adipate) (PBA) as a polymeric plasticizer was compared with poly(ethylene glycol) (PEG) as a commonly used plasticizer for PLA. The reinforcement effect of CNF was evident, even at a low loading of 1 wt%. The composite mechanical properties could be efficiently tailored by properly selecting the plasticizers. The composites of high ductility (elongation > 400 %) were achieved using PEG plasticizer, whereas the composites containing PBA plasticizer exhibited relatively higher modulus, strength, and heat resistance. The plasticizers had strong effects not only on the mechanical performance but also on the crystallization behaviors of PLA.