Cellulose Nanocrystals versus Polyethylene Glycol as Toughening Agents for Poly(Lactic Acid)-Poly(Acrylic Acid) Graft Copolymer

摘要

Polylactic acid (PLA) is one of the most widely used biodegradable polymers due to the ability to synthesize it economically at industrial scale and its favorable properties for many consumer products. However, the rigid nature of PLA is not desirable for specific applications, requiring the incorporation of effective bioderived additives in order to enhance the PLA toughness and broaden applications. In this work, PLA was modified by graft polymerization of polyacrylic acid (PLA-g-PAA) to increase the hydrophilicity to promote compatibilization of cellulose nanocrystals (CNCs) or high molecular polyethylene glycol (PEG). CNCs were found to act as a nucleating agent for the PLA-g-PAA copolymer due to an enhanced compatibility with these rigid nanocrystals, thus increasing the tensile modulus and reducing toughness. This was not the case for pure PLA, for which the toughness was increased up to 125% for a 1% CNC loading. PEG successfully increased toughness of the PLA-g-PAA by more than 34 times that of neat PLA and PLA-g-PAA with a substantial yet not critical reduction in strength and modulus for a wide range of applications.