Rehological Model for the Prediction of Polyethylene Blown Film, 1997 Polymers, Laminations & Coatings Conference Proceedings

Development of new or improved blown film products is an expensive and time-consuming exercise for converters. Often, many experiments and trial runs have to be performed, accompanied by evaluations of the resulting film samples. In case no lab-scale blown film line is available, also valuable production time is lost. Utilization of model calculations relating polymer type and machine parameters to properties of films obviously is an interesting option to streamline the development process of films. The practical use of model calculations depends on reliability and versatility of the model used. In this paper, a rheological model is presented that was developed for LDPE, and relates rheological PE properties, processing conditions and die geometry to mechanical and optical properties of the films. Validation of the model on different blown film lines has proven its reliability for LDPE. Furthermore, the model has been extended to binary LDPE/LLDPE blends, demonstrating its versatility for PE in general. An oversight is given of theoretical and experimental issues encountered during the development of the model, complemented with some instructive examples of practical usage.