Plasticized polylactic acid/cellulose nanocomposites prepared using melt-extrusion and liquid feeding: Mechanical, thermal and optical properties

Plasticized polylactic acid (PLA) and its nanocomposite based on cellulose nanofibers (CNF) and glycerol triacetate (GTA) were prepared using a co-rotating twin-screw extruder. GTA was used as a plasticizer, a processing aid to facilitate nanofiber dispersion and as a liquid medium for their feeding. The optical, thermal and mechanical properties were characterized and the toughening mechanism was studied. The addition of GTA (20%) and CNF (1%) resulted in increased degree of crystallinity and decreased optical transparency. Furthermore, these additives showed a positive effect on the elongation at break and toughness, which increased from 2% to 31% and from I to 8 MJ/m(3), respectively. The combination of slippage of the nanofiber matrix-interface and a massive crazing effect as a result of the presence of CNF is suggested for PLA toughening. CNF were expected to restrict the spherulite growth and therefore enhance the craze nucleation. (C) 2014 Elsevier Ltd. All rights reserved.