A Comparative Study of the Effect of Compounding Methods and Processing of PLA/GNPs on the Micromorphology and Electrical Conductivity

Abstract

In this work, the effects of different compounding and processing techniques on the DC electrical conductivity and density of polylactic acid (PLA)/ graphene nanoplatelets (GNPs) composites were studied. It is found from the study that compounding by solution mixing via an ultrasonication technique can provide slightly higher DC electrical conductivity after compression molding than mixing through a twin-screw extruder due to better dispersion quality. In addition, a composite pellet from twin screw extrusion showed a slight increase in DC electrical conductivity and anisotropy when processed by filament extrusion due to the shear alignment of GNPs during the extrusion. The fused deposition modeling (FDM) process yields high anisotropy because the crystallization along the printing path allows gaps and polymer coating between the extruded lines and layers. It was found that the 7.5 wt% GNPs composites exhibited the best properties because it provides the best dispersion quality to meet the percolation threshold. Furthermore, the micromorphology of each sample was also studied to observe the dispersion and porosity inside the composite provided by each fabrication technique. This study can be used as a reference for compounding and processing techniques.