Biocomposites of Poly(Lactic Acid) and Cellulose Nanofibers from Cassava Pulp

Abstract

Cellulose nanofibers (CNFs) were used as biobased fillers to prepare poly(lactic acid) (PLA)-based biocomposites. Cellulose nanofibers were extracted from cassava pulp (CP) by acid hydrolysis method. Before submitted to acid treatment, CP was pre-treated by alkali and bleaching treatments. The biocomposites were prepared by melt mixing, followed by hot melt pressing. In order to improve the compatibility of CNFs with PLA matrix, glycidyl methacrylate (GMA) grafted poly (lactic acid) (PLA-g-GMA) was used as a compatibilizer. PLA-g-GMA was prepared by grafting of GMA onto PLA chain via melt mixing using an internal mixer. Transmission electron microscopy (TEM) micrograph shows that most nanofibers with the diameter in the range of 10-30 nm and immeasurable length were obtained. The appearance of two new peaks at 49.07 and 44.71 ppm in the carbon-13 nuclear magnetic resonance (13C-NMR) spectrum of PLA-g-GMA, which represent the carbons of the epoxy group of GMA, confirms that GMA was successfully grafted onto PLA chain. The morphology of biocomposites, characterized by scanning electron microscopy (SEM), reveals that without using PLA-g-GMA, the poor dispersion of CNFs in PLA matrix was observed. In contrast to that, with using PLA-g-GMA, the dispersion of CNFs in PLA matrix was improved. Moreover, the impact strength results show that by incorporating 1.0 wt% CNFs into PLA matrix and using PLA-g-GMA as a compatibilizer, the impact strength of biocomposites was slightly enhanced compared to that of pure PLA.