Polylactic acid/polyurethane blend reinforced with cellulose nanocrystals with semi-interpenetrating polymer network (S-IPN) structure

The aim of the current work was to prepare and characterize a cellulose nanocrystal reinforced semi-interpenetrated network (SIPN) derived from polylactic acid (PLA) and polyurethane (PU) polymers. SIPN films were prepared using solvent casting from 1,4-dioxane solution. The morphology, mechanical and thermal properties of the neat SIPN and its nanocomposite were characterized. A novel dispersion method was used, for the first time, to disperse the CNCs into the polyol. This method led to well dispersed CNCs in the SIPN, and at 1 wt% CNC concentration, the elastic modulus of the nanocomposite was improved by 54% over an unreinforced SIPN. Additionally, the results indicated that the toughness of PLA, which is the main polymer phase, was improved. However, in the nanocomposite, CNCs formed a strong network and reinforced the PU phase, which resulted in a lower toughness of the final material. The storage modulus of the SIPN nanocomposite was higher than that of the neat PLA at temperatures higher than 55 degrees C up to 100 degrees C. This increase in thermomechanical properties indicates that the reinforced PU network in the PLA matrix can enhance the thermal behavior of material. (c) 2016 Elsevier Ltd. All rights reserved.