PLA toughened by bamboo cellulose nanowhiskers: Role of silane compatibilization on the PLA bionanocomposite properties

To toughen brittle poly(lactic acid) (PLA) composites, surface-modified bamboo cellulose nanowhiskers (BCNW) were introduced into a PLA matrix. The BCNW was treated with (3-mercaptopropyl)trimethoxysilane (A-189) at five concentrations between 1 wt% to 16 wt% to improve compatibility. Silylated BCNW-toughened PLA composite films were further fabricated by solution casting. The coupled reaction between A-189 and cellulose via Si-O-C bonding and hydrogen bonding was confirmed. BCNW was silylated uniformly and maintained its original morphology. With increasing concentration, BCNW became smooth; however, with excessive coupling agent, the BCNW surface became rough. Elongation at break was inversely proportional to tensile strength and tensile modulus. Elongation at break increased to 250.8% after the 4 wt% A-189 treatment compared to 12.35% with untreated composites. The C/O ratio of BCNW decreased after coupling agent treatment. There were physical interlocks and hydrogen bonding between two phases. A wire-drawing phenomenon was observed on the tensile fractural surface. The thermal degradation stability decreased with the increasing treatment concentration.