The Effect of Bacterial Cellulose on the Mechanical and Thermal Expansion Properties of Kenaf/Polylactic Acid Composites

Abstract

The reinforcement of PLA matrix with natural fibers aims to generate the sustainable biocomposites. Kenaf fiber (KF) and bacterial cellulose (BC) were employed to reinforce and diminish the usage of PLA matrix. Particularly, BC is nano-cellulose which was anticipated to increased interfacial area and therefore low volume fractions of additives. That was consequently to attain mechanical property improvement. Thus, the incorporation of KF and BC reinforced PLA composites was investigated. The extrusion method was utilized and materials were mixed outside prior to adding. The specimens were examined mechanical testing, Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Thermo Gravimetric Analysis (TGA) and Scanning Electron Microscopes (SEM). The mechanical study revealed that the increment of elastic modulus increased concomitantly with the augmentation of KF content. Interestingly, PLA/KF/BC sample at ratio of 60/39/1 wt.% was efficiently to maintain tensile and flexural strength comparing to 50% reduction of without BC sample with equal fiber volume. Therefore, it could recognize that mechanical properties was improved by using low amount of nano-cellulose. This would be a high aspect ratio of BC that capable to connect between PLA matrix and KF which enhanced a large contact surface and therefore excellent coherence. The temperature dependence of storage, loss and tan delta was determined by DMA. A decrease of storage modulus was consistent with increasing of temperature, result from softening of the composites. Loss modulus was increased approximately at Tg which related to storage modulus cause. In addition, the tan delta peaks of PLA and composites were around 60°C and it did not significantly shift when emerged of fiber. DSC of both composites indicated an influence of fiber on the crystallization and enthalpy. On the other hand, glass transition and melting temperature did not significantly affect. The composites exhibited a small reduction of thermal stability when examined by TGA analysis. Notwithstanding, BC showed an improvement of thermal stability of PLA/KF/BC sample at 40 wt.% total fiber content. The linkage of BC between PLA matrix and KF was monitored by SEM.