Experiments and Modelling of Calender Processing for Shear Thinning Thermoplastics between Counter Rotating Rolls with Differential Velocities

摘要

This paper is concerned with a floor application calendering processing using both a PVC and a Polyolefin formulation within a two roll calender. The rheology of both formulations was measured using the Rheoplast, a specific capillary rheometer. Experiments with various velocity differentials were performed and the roll separating force and the sheet exit temperature were measured for each case. An isothermal model based on the lubrication approximations hypothesis together with a power-law behavior for the molten polymer has been developed. Due to the difference between the rotation velocities of the two cylinders, the problem is no longer symmetric and the integration of the generalized Reynolds equation requires taking into account various velocity profiles. The resulting pressure profile enables computation of the roll separating force. The agreement between the model and experiments performed with the PVC formulation at various velocity differentials is fair; however for the Polyolefin formulation there is a significant difference which means that the model for this new formulation needs to be improved.