Biocomposites composed of polyamide 11 and cellulose nanofibers pretreated with a cationic reagents

Abstract

Cellulose nanofibers (CNFs) have many useful properties, including high strength and low thermal expansion. They are environmentally friendly, renewable, safe, and biodegradable. The focus of this study was to develop lightweight thermoplastic polymer composites with good mechanical properties by incorporating CNFs pretreated with a cationic reagent. Polyamide 11 (PA11) was mixed with the surface-treated CNFs using a twin-screw extruder and the resulting pellets were injection molded. Four different cationic reagents were used to modify the hydroxyl groups on the CNF surface, which resulted in better dispersion of the CNFs in the composites owing to reduced hydrogen bonding between the CNFs. The best cationic reagent for the preparation of CNF-reinforced composites was poly (N-methyl diallyl amine)-epichlorohydrin. The polymer consisted of repeating cationic quaternary ammonium salt units and was grafted with epichlorohydrin, which contained a reactive epoxy group. The molten viscosity of the composite prepared using poly (N-methyl diallyl amine)-epichlorohydrin was the highest of all the prepared composites. The high viscosity was attributed to the dispersed state of the CNFs in the composites and interfacial interactions between CNF and the PA11 matrix. The mechanical properties, fracture aspect, and thermal properties of the composites were strongly related to the molten viscosity. Cationic pretreatment of the surface of the CNFs enhanced the dispersion of the fibers and significantly improved the mechanical and thermal properties of the composites.