Abstract
The quality of a wide film manufactured is determined by the flatness of the film thickness along the width of the film. To control the film thickness in the lip-heater method, an uniform distribution of melted polymer flow velocity in the gap between die lips is required.
In this paper, a mathematical model of polymer flow in the lip gap is derived. The analytical model is as follows;
The flow model in the lip gap is divided into 3 sections in the flow direction because the lip gap is gradually narrowed along the flow. The flow in each section is approximated by the flow between parallel planes. The lip model is also divided into 3 sections along the flow direction and divided into the number of heaters in the direction of width in order to get a lumped model for temperature dynamics of the lip in which heaters are buried. The polymer viscosity is given by the power law equation. The polymer temperature distribution in the lip gap is obtained by the unsteady energy balance equation and the steady velocity solution. The comparison between the calculated values and the experimental data expresses that the proposed model has enough accuracy and can be used for the actual control system design.
