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Enhancing gas barrier performance of polylactic acid/lignin composite films through cooperative effect of compatibilization and nucleation
Author(s) -
Wang Ningning,
Zhang Caili,
Weng Yunxuan
Publication year - 2021
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.50199
Subject(s) - polylactic acid , crystallinity , materials science , composite number , compatibilization , differential scanning calorimetry , composite material , ultimate tensile strength , nucleation , glycidyl methacrylate , chemical engineering , polymer chemistry , polymer , polymerization , copolymer , chemistry , polymer blend , organic chemistry , engineering , thermodynamics , physics
Abstract In this work, lignin was used as a heterogeneous nucleating agent to increase polylactic acid (PLA) crystallinity. To enhance the gas barrier performance of PLA/LG composite films, two graft copolymers, polylactide‐graft‐glycidyl methacrylate (PLA‐g‐GMA) and polylactide‐graft‐poly (ethylene glycol) methyl ether methacrylate (PLA‐g‐PEGMA) were successfully synthesized and separately used as compatibilizers to modify PLA/LG composite properties such as interfacial adhesion, crystallinity, and mechanical properties. Since crystallites can act as obstacles to gas diffusion, the higher the crystallinity of the polymer matrix, the better gas barrier performance of the composite film will be. The crystallinity and crystalline structure of the PLA matrix was demonstrated by wide‐angle X‐ray diffraction and differential scanning calorimetry results. Since LG particles can act as efficient heterogeneous crystal nucleating agents, a roughly 50% reduction in oxygen permeability ( P O2 ) was obtained by adding 1 phr LG to the PLA matrix (PLA/1LG). Following addition of 10 phr PLA‐g‐GMA to the PLA/LG composite, PLA/PLA‐g‐GMA/LG composite films showed lower gas barrier properties than PLA/LG composites without added compatibilizer. Moreover, the interfacial adhesion of PLA/LG composites was significantly improved after addition of PLA‐g‐GMA. Therefore, PLA/PLA‐g‐GMA/3LG showed the highest tensile strength, 33% higher than that of neat PLA. Following addition of 10 phr PLA‐g‐PEGMA to the PLA/LG composite, the long liner side chains of PLA‐g‐PEGMA were able to act as nucleating agents for PLA to promote the crystallization of PLA. Accordingly, PLA/PLA‐g‐PEGMA/3LG with 3 phr LG showed a roughly 86% reduction in P O2 when compared with neat PLA film.