Effect of injection molding parameters on nanofillers dispersion in masterbatch based PP-clay nanocomposites

Abstract

The effect of injection molding parameters (screw rotational speed, back pressure, injec-tion flow rate and hold- ing pressure) on the nanofiller dispersion of melt-mixed PP/clay nanocomposites was investigated. The nanocomposites containing 4 wt% clay were obtained by dilution of a PP/clay masterbatch into a PP matrix. The evaluation of the dispersion degree was obtained from dynamic rheological measurements. The storage modulus and complex viscosity exhibit signifi- cant dependence on the injection molding parameters. PP/clay nanocomposite molded using more severe injection parame- ters (high shear and long residence time) displays the highest storage modulus and complex viscosity, which illustrates the improved dispersion of clay platelets. This better dispersion leads to better mechanical properties particularly higher Young modulus, tensile strength and unnotched impact strength. A Taguchi analysis was used to identify the influence of individ- ual process parameters. The major individual parameter is the injection flow rate, whose increase improves nanoclay dis- persion. The combination of high back pressure and high screw rotational speed is also necessary to optimize the dispersion of clay nanoplatelets.