Rheological Properties and Extrudate Swell of PHBV-Bagasse Composites

Polyhydroxybutylate-co-hydroxyvalerate (PHBV) is biodegradable aliphatic polyester that produced by a wide range of microorganism. In this research aims to study the melt rheological and extrudate swelling behavior of PHBV filled with bagasse. The composites prepared by melt mixing (Two roll mill and Twin screw extruder). The effects of processing techniques for PHBV powder and bagasse loading, aspect ratio (particle size i.e. x<150μm, 150<x<250μm and x>250μm) and, surface treatment of bagasse were investigated by capillary rheometry at 180 °C. The dispersion of the bagasse was inspected by the scanning electron microscopy (SEM). A different compositions based on PHBV/bagasse were investigated according to the following weight ratios, i.e. 100/0, 95/5, 90/10, 80/20 and 70/30 wt% respectively. The results showed that the PHBV/bagasse composites exhibit pseudoplastic behaviour as the shear stress and extrudate swell increased with increasing shear rate while shear viscosity decreased. The apparent shear stress and apparent shear viscosity increased with increasing bagasse loading and, at a given apparent shear rate, the apparent shear stress increased slightly with increasing bagasse particle size. However, detrimental bagasse agglomeration was clearly observed to take place for sample with bagasse loading in excess of 20 wt%. The surface treatment of bagasse was carried out using silane coupling agent and benzoic acid. The results proved the effect of functionalization on the interfacial adhesion between PHBV and bagasse. Also, there was also further confirmed by rheology behaviour and SEM-EDS image.