Rheological, Mechanical, and Thermal Properties of Polylactide/Cellulose Nanofiber Biocomposites

Biocomposites based on polylactide (PLA) and cellulose nanofibers (CNFs) were prepared via a solution method. The effects of CNFs on rheological, mechanical, thermal, and optical properties of PLA were investigated. Scanning electron microscopy showed that the CNFs were fairly dispersed/distributed in the PLA. Significant increases in the rheological properties of PLA/CNF composites and a remarkable shear-thinning behavior were observed. Also, apparent yield stress and a transition from liquid-to solid-like behavior indicated a strong 3D network of CNFs. At room temperature, the storage and Young moduli were increased by 50% for the composite containing 5 wt% CNFs as compared to the neat PLA, whereas the tensile strength was increased up to 31%. The Krenchel model was shown to predict well the Young modulus for lower concentrations of CNFs. Moreover, relative to the neat PLA the storage modulus in flexion at 70 degrees C increased by 264% for PLA containing 5 wt% CNFs. Increased crystalline content and a positive shift of the crystallization temperature by incorporating the CNFs in PLA were observed. Also, good light transparency was retained for these PLA/CNF biocomposites. These results show that the preparation method employed in this work leads to PLA/CNF composites with considerably enhanced properties. (C) 2016 Society of Plastics Engineers