Heat Transfer in Twin Screw Compounding Extruders

In this paper an analytical theory is presented that allows prediction of melt temperature distribution in screw extruders; the theory applies to both single screw extruders (SSE) and twin screw extruders (TSE). The theory is based on the analysis of two distinct regions. Region 1 the thermal penetration layer at the barrel surface; this is the melt film affected by conductive heat transfer with the barrel. Region 2 is the inner region that is exposed to largely adiabatic conditions. This theory shows that cooling of the melt traveling through the screw channels in a high speed TSE is minimal. As a result, it is difficult to cool down the polymer melt in a high speed TSE. The theory also allows quantitative evaluation of the temperature dependence of the viscosity on the melt temperatures along the length of the extruder.