Optimizing torque rheometry parameters for assessing the rheological characteristics and extrusion processability of wood plastic composites

The rheological behavior of wood plastic composites' (WPCs') melts is closely associated with extrusion processability, especially in highly filled systems. This study investigated the extrusion processibility and the effects of test conditions and typical WPC additives on the torque rheological behavior of wood flour/high-density polyethylene (WF/HDPE) mixing melts compounded using a twin-screw extruder. Both equilibrium melt temperature (T-e) and equilibrium torque (M-a) at steady state increased with WF content. Addition of 2% lubricant TPW604 based on the total weight of WF and HDPE matrix resulted in a decrease in measured T-e and M-a, showing a reduction in shear heating in mixing chamber. Adding 4% maleic anhydride grafted polyethylene (MAPE) as compatibilizer resulted in an increase in measured T-e and M-a. In this study, adding lubricant TPW604 and/or compatibilizer MAPE can improve the extrusion processability of highly filled WF/HDPE melts. For a WPC system with preset compositions, its M-a value can be used to evaluate its extrusion processability. The results provide both knowledge about the compounding procedure and practical methods for evaluating the effectiveness of WPC additives, the flow performance, and extrusion processability of highly filled WPC melts.