The solid‐state mixing characteristic of two rotor continuous mixer and its influence on microstructure of HDPE/CaCO₃ composite

In this article, the solid‐state mixing characteristics of two rotor continuous mixer were studied by revealing the change of CaCO₃ particles size and its surface properties. High‐density polyethylene/calcium carbonate (HDPE/CaCO₃) composites were fabricated for the study. The characterized CaCO₃ particles samples were taken from different axial positions of solid‐state mixing zone. Particle size and morphology of CaCO₃ particles were investigated by laser particle sizer and scanning electrical microscope (SEM). The decrease of CaCO₃ particles size indicated that fillers deagglomerated along the solid‐state mixing zone. The surface properties of CaCO₃ particles were studied by Fourier transform infrared spectroscopy (FTIR), water contact angle and thermogravimetric analysis. The appearance of HDPE characteristic peaks in the FTIR spectrum of CaCO₃ particles showed that the filler surface was coated by HDPE during solid‐state mixing, which made CaCO₃ particles less hydrophilic. Deagglomeration and surface coating amount of CaCO₃ particles were influenced by process parameters, and the best results were obtained at feed rate 1.58 kg/h and rotor speed 700 rpm. Furthermore, SEM and dynamic rheology measurement of HDPE/CaCO₃ composites were conducted to investigate the composite microstructure. Higher complex viscosity and more obvious shear thinning behavior were the indications of improved CaCO₃–HDPE compatibility and filler–filler interaction after solid‐state mixing process. POLYM. COMPOS., 40:3296–3305, 2019. © 2019 Society of Plastics Engineers