Structural characterization of mono and multi-layer bi-oriented blow films of PP/PE blends

Abstract

The commercial process to produce polyethylene films is blow co-extrusion. These films are excellent for hot seals but do not have good mechanical properties. On the other hand polypropylene films also obtained via inverted blow co-extrusion present very good mechanical properties, but heat seal only at relatively high temperatures, limiting their commercial applications. In order to get high performance at a low cost, the two polymers are combined into blends. Thus multi-layer polymer films are produced in which the structural internal layer is made by rich polypropylene PP/PE blends to ensure good mechanical properties and the external layers of polyethylene to warranty good hot sealing. The co-extrusion process and the consequent bi-orientation affect the crystallization of the various phases providing unique structural properties to the films. The purpose of this project is to characterize the crystalline structure of mono and multi-layer bi-oriented blow films of PP/PE blends. The structures that will be evaluated are bit-oriented films formed by: i) mono-layered structure of PP/PE blends rich in polypropylene, ii) three-layered structure being the internal layer of a PP/PE blend, and the external ones of monophasic polyethylene. The characterization of the films will be done by Differential Scanning Calorimetry DSC in order to identify the polymers melt temperature, Polarized Light Optical Microscopy PLOM with the hot stage to measure the birefringence, Polarized Infrared Spectroscopy FTIRpol to measure the dichroic ratio and X-Ray Diffraction for the crystalline phase's identification. For that we rely upon the infra-structure and equipment of the Departamento de Engenharia de Materiais (DEMA) of the Universidade Federal de São Carlos (UFSCar). (AU)