Thermal properties of spark plasma -sintered polylactide/graphene composites

Abstract

Polylactic acid (PLA)/graphene GNP nanocomposites with 0, 3, 5, 7% wt.% GNP concentrations have been prepared using the novel Spark Plasma Sintering (SPS) technique. This was performed under a fixed operating temperature of 160 °C, pressure of 25 MPa, heating rate of 20 °C/min and holding time of 10 min. The appearance of peak around 26.5° for PLA/GNP nanocomposites in the X-ray diffraction (XRD) analysis is typical of the presence of GNP. The thermogravimetric-fourier transform infrared radiation (TG-FTIR) analysis and differential scanning calorimetry (DSC) were carried out to investigate the thermal behaviour of the sintered nanocomposite. The surface morphology of the nanocomposite was performed using the scanning electron microscopy (SEM). The result shows that the thermal degradation temperature of PLA has been enhanced by an approximate double-fold increase via the novel SPS technique. The crystallinity and melt temperature of the sintered nanocomposites only improves slightly as compared to sintered pure PLA. The thermal stability, residual content, and stiffness of the nanocomposites also increases with increasing GNP filler content in the PLA matrix. Furthermore, the dynamic mechanical analysis (DMA) confirmed a better enhancement in thermal stability of the nanocomposites through increase in glass transition temperature than the DSC report. This is own to the better sensitivity of DMA to local segmentation motion compared to DSC. However, the SPS processing technique can be said to have contributed greatly to the enhancement in thermal stability than the inclusion of GNP as-sintered pure PLA exhibited similar patterns and close thermal properties to the sintered PLA/GNP nanocomposites samples. Furthermore, this process route enables the development of highly densified, lightweight polymer nanocomposite material within a short processing time.