In this study, the finite element method ws used to investigate the effects of screw speed, entering peroxide distribution, and pressure-to-drag flow ratio on the mixing characteristics of steady non-isothermal reactive flows in a forward conveying element of a self-wiping twin screw extruder. The reaction considered was the peroxide-initiated degradation of a commodity polypropylene resin. The predicted average degree-of-freedom profiles from the simulations largely confirmed to expectations. The average flow efficiencies for all runs were found to remain at values close to that for two-dimensional flow, with fluctuations being observed in the channel intermeshing regions. No significant effect of either screw speed or peroxide distribution was found on the flow efficiencies; however, the pressure-to-drag flow ratio was found to have a significant influence. (C) 2000 John Wiley & Sons, Inc.