Thermoplastic Composites of Polyamide-12 Reinforced by Cellulose Nanofibers with Cationic Surface Modification

Cellulose nanofibers (CNFs) have many useful properties, including high strength and low thermal expansion, and are also environmentally friendly, readily renewable, safe, and biodegradable. The focus of this study was the development of lightweight thermoplastic polymer composites with good mechanical properties based on the incorporation of CNFs that have undergone surface pretreatment with a cationic reagent. The polyamide (PA12) was mixed with surface-treated CNFs using a twin screw extruder and the resulting pellets were injection molded. The Izod impact strength without notch of CNF-based composites exceeded that of composites incorporating organophilic montmorillonite (OMMT), a representative nanocomposite material. When the Izod impact test without notch, the impact hammer was stopped by the specimen with incorporation of surface treated CNF. Furthermore, the bending modulus and strength were equal to or greater than that of OMMT composites. The heat distortion temperature was improved as 33 degrees C from neat PA12, and moreover improved as 29 degrees C from OMMT composites. Cationic pretreatment of the CNF surfaces was found to increase the dispersion of the fibers and also to greatly improve the mechanical and thermal properties of the composites. (C) 2014 Wiley Periodicals, Inc.