Mechanical and Thermal Properties of PLA/PBS Co-continuous Blends Adding Nucleating Agent

Abstract

The influence of nucleating agents (nano-sized calcium carbonate and sodium benzoate) on mechanical and thermal properties of PLA/PBS co-continuous blends was investigated. PLA/PBS 60/40, 50/50, 40/60 wt% blends were compounded with NPCC or SB (0.5 and 1.0 phr) in a twin-screw extruder and fabricated into thin sheets by hot pressing. DSC was used to study glass transition temperature (Tg) and percentage of crystallinity (%Xc) of the blends. Morphology of fractured surface was examined using SEM. It is found that the PLA/PBS 50/50 wt% blend was co- continuous structure even incorporating NPCC or SB of 0.5 and 1.0 phr. Adding SB of 1.0 phr caused the PLA dispersed phases in the PLA/PBS 40/60 wt% to be smaller droplets distributed in the continuous PBS matrix. On the other hand, adding NPCC of 1.0 phr into PLA/PBS 60/40 wt% produced elongated continuous phase of PBS stripped out of PLA matrix. Adding SB into PLA reduced Tg from 63 to 60°C, while NPCC nucleated higher %Xc of PLA phases in all blends. Tensile strength, elongation at break and energy at break of the blends were reduced when filled with NPCC and SB. This is due to increasing in crystallinity of the PLA phases and the presence of stress concentrators in the blends.