The Prediction of Film Thickness after Transverse Stretching with a Consideration of Heated Air Flow in a Tenter

Abstract

The thickness of Polypropylene (PP) film after stretching was predicted in transverse direction (TD) stretching with a consideration of heated air flow in a tenter, in order to study TD stretching process under more realistic heat transfer conditions than previous study's heat transfer distribution which is calculated by using impinging jet and wall jet models. The heated air flow in the tenter was analyzed with a finite volume method, in order to calculate the distribution of heat transfer coefficient on film. The distribution obtained was more realistic than previous study's distribution. The film thickness after stretching was analyzed by applying the distribution of heat transfer coefficient based on air flow analysis and previous study's distribution. An experimental result agrees better with the calculation which used the distribution of heat transfer coefficient based on air flow analysis than the calculation of previous study's distribution. It is revealed that the distribution of heat transfer coefficient and the temperature difference on film in the stretching have strong influence on the uniformity of film thickness.