Thermodynamic aspects in extrusion of wall†slipping materials

Relevant calculations are made based on the application of the first law of thermodynamics to a steady polymer flow through a plasticating extruder. The results obtained for various processing conditions for poly(vinyl chloride), which exhibits a slip at the wall during flow at lower temperatures, are compared with polyethylene showing no such slip. For a wall‐slipping material, it is observed that, with increasing throughputs the addition of enthalpy per unit mechanical energy increases (1), the net‐specific thermal energy input increases (2), and the specific mechanical energy required shows a decreasing trend (3). Contrary behavior is found in the case of non‐slipping materials. Copyright © 1982 Society of Plastics Engineers, Inc.