Interfacial enhancement of bamboo flour/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biocomposites enabled by synergistic treatment via delignification and PHBV-based coupling agent impregnation

Novel development of high-loading bamboo flour/PHBV biocomposites. • Synergistic treatment of bamboo flour via delignification and impregnation of coupling agents. • Surface roughness and chemical interactions benefitted interfacial adhesion. • Enhanced interfacial bonding contributed to mechanical and thermal property improvement. This paper presents a novel development of bamboo flour/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biocomposites with a particular focus on addressing the interfacial bonding through a synergistic treatment. The synergistic strategy involves the delignification of bamboo flour followed by impregnation of PHBV-based coupling agents synthesised in this work, including maleic anhydride (MA)-grafted PHBV (MA- g -PHBV), acrylic acid (AA) grafted-PHBV (AA- g -PHBV) and itaconic anhydride (IA) grafted-PHBV (IA- g -PHBV). Chemical structural analyses of bamboo flour suggested the removal of lignin and the possible interactions between surface hydroxyl groups and the introduced anhydride/carboxyl groups after the synergistic treatment. Microstructure analysis suggested the treated bamboo flour with increased surface roughness had better interfacial adhesion with PHBV matrix in the composites, which was further confirmed by their lower loss factor. The tensile strength and flexural strength of MA- g -PHBV modified delignified bamboo flour/PHBV composite were increased by 333.3% and 250.4% respectively, compared to those of the untreated counterpart. The improved interfacial bonding also resulted in the shift of composite failure mechanism from fibre pull-out to fibre breakage. The work provides a feasible and effective modification approach of lignocellulosic fibres for enhancing fibre-matrix interfacial bonding in biobased and biodegradable composites.