Characteristic Profiles of Polymer Flow in Plain Channels
Elzbieta Bociaga, Robert Sikora
Technical University of Czestochowa
Poland

Keywords: polymer, flow, channel

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The flow of viscoelastic polymer in channels of processing tools, especially in injection molds, is unstable and no isothermal. Instability is a result of process periodicity and short time of flow duration. No isothermal character of the flow is connected with the heat generated from friction inside polymer and between polymer and channel walls, and also with the temperature difference between the channel and polymer. Liquid polymer, entering the channel, contacts with its walls of much lower temperature and goes under progressive solidification. As a result of this the solid layer of polymer, adhering to the channel wall, is created. The layer makes heat insulation for the polymer flowing over its inner wall. Such layer arises in natural way in cold channels or is created in intentional way in hot channels – heated and insulated. Distribution of flow velocity in the channel, shear rate, shear stress and polymer temperature depends mainly on temperature gradient between the channel wall and polymer, polymer viscosity and density, thermal properties of polymer and channel material such as thermal conductivity, specific heat. Characteristic profiles of polymer flow were determined in the cross section of the channel. They should help to understand the heterogeneity of polymer structure and properties created during the flow.