Abstract
Poly(lactic acid) (PLA) has attracted much attention recently as green plastic, but its use is still limited because of its low crystallinity and productivity. A modified PLA compound for injection molding was developed by adding nucleating agents and a plasticizer into PLA. Furthermore, addition of filler compounds into PLA was examined to increase the strength and the modulus of PLA. In this study, modified PLA composites containing amorphous cellulose and crystalline cellulose fillers were investigated. The amorphous cellulose filler was made by a mechanochemical reaction. Compared to the modified PLA without cellulose, the PLA/crystalline cellulose composite had increased stiffness and heat resistance, but greatly decreased fracture toughness. The decrease of fracture toughness of the PLA/amorphous cellulose composite was much smaller than that of the PLA/crystalline cellulose composite. To explain these results, scanning electron microscopy and atomic force microscopy were performed. The microscopy observations indicated that the interface of PLA and amorphous cellulose was more cohesive and this prevented the occurrence of microcracks. Effect of further pulverization of amorphous cellulose was also investigated. By using microamorphous cellulose, the impact strength of PLA/amorphous cellulose composite improved by 46 percent.
