Structure-properties relationship of hybrid talc/calcium carbonate filled impact modified PVC composites

Abstract

The main objective of this study was to investigate and compare the mechanical properties and processability of single-filler and hybrid poly(vinyl chloride) (PVC) composites. Calcium carbonate (CaCO3) was used in this study to improve the impact strength of PVC while talc was used to improve stiffness. Filler was added into PVC at a constant loading level of 30phr. SM90 showed the most optimum properties in terms of impact strength and flexural modulus among all grades of CaCO3 selected for hybrid study. Tests specimens were prepared by using dry blending, two roll milling and compression moulding processes. Flexural, impact and tensile tests were then performed to determine and compare the effect of fillers on mechanical properties of PVC composites. Talc filled PVC composite showed the highest flexural modulus but the lowest impact strength. The impact strength of hybrid PVC composites gradually increased with increasing SM90 content, but the flexural modulus showed an opposite behaviour. The flexural strength and impact strength were the highest among the hybrids when the talc/SM90 weight ratio was 20:10. The distribution and dispersion of the fillers in PVC matrix were observed by using SEM. The well dispersion and interfacial adhesion of SM90 and talc particles in PVC matrix had contributed and helped in improving the stiffness and the impact strength of PVC composite. The fusion time of hybrid talc/SM90 filled PVC composite gradually increased as the talc content was gradually replaced by SM90. However, the hybrid (10phr talc: 20phr SM90) filled PVC composite showed the longest fusion time among all PVC composites. TGA, DSC and HDT tests were also carried out to investigate the thermal properties of PVC composites. The incorporation of talc and CaCO3 were found to improve the thermal stability and rigidity of PVC composites.