A Rheological Model for the Prediction of Polyethylene Blown Film Properties

Abstract

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. If no lab-scale blown film line is available, valuable production time is lost while seeking out optimum processing parameters. 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 Theological model is presented that was developed for low density polyethylene (LDPE), and relates rheological 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 (linear low density polyethylene) 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.

A novel method for industrial manufacturing of thermoplastic multilayer films: Processing, microstructure, and properties

“…Other studies focused on correlations among microstructures, properties, and blowing processes after the melt leaves the die [16][17][18][19][20][21][22][23]. For example, Zhang et al [18,19] prepared polypropylene/linear low-density polyethylene (LLDPE) and LDPE/ polyethylene terephthalate multilayer films and discussed the orientation structures and crystal morphologies of films at different BURs, DDRs, and frost line heights.…”

Evaluation of Stresses in a Two-Layer Co-Extruded LDPE Melt Blown Film

“…Babel and Campbell [2] reported a correlation between the amount of plastic strain and the ultimate physical properties of the film. Kuijk et al [3] were able to demonstrate that mechanical properties such as machine and transverse direction moduli, elongation at break, tensile strength yield stress and tear resistance, correlate well with the stress level in the polymer melt at the freeze line. So the determination of the stress generated during the blown film process, either from experimental data or from numerical calculation, could give us insight into the properties of the film produced.…”

Application of variational principles in modeling of the film blowing process for high stalk bubbles

“…During the biaxial orientation of the film, the bubble is cooled by air flowing along the film. The height at which the solidification starts is referred to as the freezeline and the stresses frozen at this area are inextricably related to the final mechanical and optical properties of the film [1][2][3]. With the aim to understand more deeply the stability of the film blowing process and the relationship between machine design, processing parameters, materials and final film properties, intensive experimental as well as theoretical [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] effort has been done in past 40 years.…”