Influence of Internal Mixing Condition on Properties of Conductive Biocomposites between Poly(Lactic Acid) and Hybrid Graphene

Abstract

The objective of this research was to investigate the influence of mixing condition on mechanical, thermal, and electrical properties of the biocomposite between poly(lactic acid) (PLA) and hybrid graphene (HG). PLA/HG composites of a fixed weight ratio (95/5 wt%) was mixed using an internal mixer, which the mixing temperatures (170, 180 and 200°C) and the rotor speeds (40, 60 and 80 rpm) were varied. It was found that the increase of E' before glass transition was attributed to the reinforcing effect of the HG. The faster the rotor speed was the higher storage modulus (E') was achieved at the lowest mixing temperature. The E' did not linearly depend on the rotor speed when mixing at higher temperature. As expected, mixing HG into PLA reduced the surface electrical resistivity. The mixing at 170°C with any rotor speed and mixing at 180°C with rotor speed of 40 or 60 rpm produced the composites in the same surface electrical resistivity, however, there was no significant difference when mixing at 200°C. From DSC analysis, there was a trend that the degree of crystallinity of the PLA/HG composites prepared at the lowest mixing temperature was higher than those prepared at the relatively higher mixing temperatures.