Influence of functionalised lignin on strength and antioxidant properties of polylactic acid films

Currently, it is challenging to make biodegradable polylactic acids (PLA) composite films which possess high strength and toughness. To achieve the same, Lignin is unrivalled reinforcing filler which can be used in the bioplastic because of its high mechanical strength and antioxidant properties. Here, lignin has been in situ polymerized with L-lactic acid to create lignin grafted polylactic acid co-polymers which have been later combined with PLA matrix to prepare composites films with improved properties. Various analysis techniques i.e. C13 NMR, 1H NMR, and FTIR were conducted on lignin grafted lactic acid copolymer which confirmed the presence of ester linkages between lignin and lactic acid. The findings show that a modest quantity of filler can increase crystallinity, while lowering glass transition temperature and cold crystallization temperature. Additionally, the PLA composite film with 12% filler content exhibited 26.4 MPa tensile strength with 17.91% elongation at break and 1.4 GPa Young's modulus. The films also demonstrated strong antioxidant qualities done through radical scavenging, making them quite viable in packaging applications.