Polypropylene/clay nanocomposites prepared in an internal mixer: Optimization of processing conditions to improve flexural modulus

Polypropylene (PP)/clay nanocomposites are usually processed by melt mixing. In this method, mixing conditions are important variables to improve nanocomposite properties. Some studies reported the effects of processing on mechanical properties of PP/clay, but there is no clear explanation on optimum conditions. This study aims to predict the optimum conditions of PP/clay nanocomposite prepared by an internal mixer using response surface methodology (DoE). The effect of mixing on flexural modulus and nanocomposite structures were analyzed. Temperature, rotation speed, and mixing time were varied. To improve interfacial bonding, polypropylene-graft-maleic anhydride (PP-g-MA) was added as a compatibilizer. PP/clay formulation was fixed at 88 wt% of PP, 9 wt% of PP-g-MA, and 3 wt% of clay. The results show that the optimum modulus was predicted at 222 °C, 83 rpm and 5 minutes, giving 2085 MPa or 18% improvement compared to control sample. XRD diffractograms showed that nanocomposite peaks shifted to lower angles, suggesting the presence of some intercalated structures that supported the resulting increase in modulus.