Effects of lubricants on the rheological and mechanical properties of wood flour/polypropylene composites

ABSTRACT The lubricant is an indispensable agent used in wood plastic composites (WPCs) to improve the processing flowability, especially with high wood content. Here, the effects of different lubricating systems on the rheological and mechanical properties of wood flour/polypropylene (WF/PP) composites are investigated. Additionally, several theoretical models are used to describe the rheological behavior. The results show that stearic acid (SA), semirefined paraffin wax (Wax), and zinc stearate (ZnSt) can decrease the equilibrium torque, complex viscosity, relaxation time, and flow activation energy of the composite melts. Compared to a single lubricant, the combination of Wax and SA lubricants exhibits lower values and the composite with 3 wt % SA and 1 wt % Wax has the best lubricating effect. The synergistic effect of the combined SA and Wax lubricants further decreases the interactive force between the molecules, indicating that multifunctional lubricating systems play a predominant role in WPCs and improve the overall processing properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47667.