High density polyethylene/micro calcium carbonate composites: A study of the morphological, thermal, and viscoelastic properties

High density polyethylene (HDPE) with micro calcium carbonate (CaCO 3) masterbatch was pellet- ized by using a twin screw extruder and different ASTM specimens were molded by an injection molding machine. The morphology of the composites was characterized by scanning electron microscopy (SEM) and Image Analysis software. The dispersion and interfacial interaction between CaCO3 and the polymer matrix were also investigated by SEM. The thermal properties of HDPE and its composites were investigated by differential scanning calorimetry (DSC). The crystallization process of the composites samples was found to be slightly different than that of the neat HDPE. Otherwise the presence of CaCO3 did not have a considerable effect on the melting behavior of the composites. Thermogravimet- ric analysis (TGA) revealed that the composites had better thermal stability than the neat HDPE resin as indicated by a higher temperature of 50% weight loss (T50%) for the composites as compared to that of the neat resin. The viscoelastic properties of the composites and HDPE were also investigated via torsional and rotational techniques. The presence of CaCO3 increased the shear modulus at low frequency of the composites at 80°C over that of the neat resin. However, at higher frequencies, the difference between the neat resin and the composites' shear modulus was less than that at low frequencies. The complex viscosity of the composite increased upon the addition of CaCO3. However, the shear sensitivities of the neat resin and the microcomposite were similar