Particle Size of Ground Bacterial Cellulose Affecting Mechanical, Thermal, and Moisture Barrier Properties of PLA/BC Biocomposites

The effect of the particle sizes of bacterial cellulose (BC) that used as reinforcement for polylactic acid (PLA) biocomposites was investigated. The content of BC in PLA was fixed at 5 phr and various BC particle sizes were investigated, i.e., <90, 106-125, 150-180, 180-250, and 250-300 μm, respectively. The results showed that tensile strength and elongation of PLA/BC biocomposites decreased with increasing the BC particle sizes from <90 to 150-180 μm. However, the particle sizes larger than 180 μm were resulted in decreased tensile strength and elongation of PLA/BC biocomposites.Whereas, the modulus decreased with an increase of all particle sizes of BC tested. From the scanning electron microscopy (SEM) the microstructures showed that loading the smaller BC particle sizes in biocomposites in PLA matrix gave the smoother biocomposites than those from the larger BC particle sizes. This implied that the smaller BC size can disperse in PLA matrix better than the larger particle size. For the thermal properties, BC had influenced on the peak crystallisation temperature of biocomposite in which the temperature of neat PLA film decreased from 119.8 to 112.2-113 °C of the derived composite films. This behaviour indicated that BC can induce crystal nucleation of the PLA polymer. However, BC did not affect on the glass transition temperature (Tg) and melting temperature (Tm). The water vapor permeability increased with an increase of the particle sizes of ground BC.