Structural characterization of bi-oriented blown films of polypropylene/polyethylene blends

Abstract

A complete system to get in real time and on-line the birefringence of polymer films during heating in a hot stage polarized light optical microscope fitted with a parallel-plate rheometer was developed. This avoids the tedious and time consuming traditional way of measuring birefringence using a compensator. It consist of fitting a photocell in the microscope tube and recording in real-time the transmitted cross-polarized light intensity during the heating scans. The measured transmitted light intensity is on-line converted into birefringence and presented. This setting was applied to measure the thermo-optical behavior of bi-oriented mono and multilayer blown films made by polypropylene/polyethylene blends. Their semi-crystalline nature shows birefringence which is dependent of the content and orientation of the crystalline phase. Upon heating, crystalline transformations mainly phase changes and melting can be detected and quantified via changes in the recorded birefringence. © 2014 American Institute of Physics.