Harnessing the synergistic power of lignin-Ecoflex blends for enhanced performance in food packaging
Qi Hua, Zhixin Huang, Jinsheng Gou, Huaiyu Zhang, Isabella Therrien, Jie Wu, Yalan Liang, Scott Renneckar
Abstract
• Hydroxyethyl lignin derivatives used for direct esterification of technical lignin. • Lignin cinnamate derivatives were melt-processable forming blends with PBAT. • Mechanical properties, oxygen barrier, WVTR, and antioxidant properties improved. • Shelf life of fresh fruit was enhanced by the presence of lignin cinnamates in PBAT packaging. In this study, a two-step chemical modification method was applied to lignin, enabling the thermal blending of lignin and Ecoflex® (PBAT) to produce films for food packaging applications. In the first step, 90 % of phenolic and carboxylic acid groups were converted into aliphatic hydroxy groups via hydroxyethylation, and in the second step, the aliphatic hydroxy groups were esterified with cinnamic acid, introducing abundant phenyl rings as well as unsaturated groups to the polymer. The modified lignin possessed an aliphatic–aromatic structure, similar to Ecoflex®, thereby enhancing the potential miscibility between these two materials. Subsequent experiments revealed that adding 20 % of modified lignin into Ecoflex® film resulted in the most significant improvement in mechanical properties, tripling the stiffness and doubling the strength. The addition of 30 % of modified lignin showed the best outcomes in UV absorption, barrier properties against oxygen and water vapor, and anti-oxidation ability. A strawberry ripening test indicated that the Ecoflex® film containing 30 % of modified lignin extended the shelf-life of strawberries from 2 days to 7 days, with better performance than the results of polyethylene bags and pure Ecoflex® films.