Preparation of cellulose nanowhiskers and their reinforcing effect in polylactide

Cellulose nanowhiskers (CNW) were isolated from microcrystalline cellulose (MCC) using acid hydrolysis and ultrasonication. Polylactide (PLA) composites were prepared by incorporating CNW (0.1 and 0.5 wt%) into a PLA matrix and casting the composite films. To investigate the effects of the CNW as reinforcement in the PLA composites, analyses of rheological properties, thermal stability, thermal behavior, and mechanical properties were performed. In rheological analysis, complex viscosity of the PLA/CNW solutions in CHCl3 was decreased with an increase in frequency and the storage modulus and loss tangent were increased with filler loading. Despite filler loading on the PLA matrix, transmittance was decreased slightly. Thermal stability was decreased with CNW loading. The nanocellulose filler did not affect glass transition or melting temperature; however, it promoted crystallization, resulting in an increase in crystallinity for the PLA composites. The tensile strength and tensile modulus of the PLA composite films increased with a rise of CNW contents. These results suggest that high performance PLA bionanocomposites with high transparency can be obtained by adding uniformly dispersed small amount of the CNW.