Thermal Effects in Calendering Viscous Fluids

Calendering (rolling) of plastics at high speeds produces blistering and peeling which are attributed to a combination of uneven temperature distribution, and effect of temperature on the physical properties of the material. In this paper the problem is examined by studying the calendering of a viscous liquid in some detail. It is shown that a thermal boundary-layer effect exists of such magnitude as to account for formation of blisters. An example is given using typical calendering dimensions and physical properties of a plastic, which yields a thermal boundary-layer thickness of the order of depth of the blisters as observed. These data furnish further qualitative confirmation to the physical argument.