Enhancing the Rheological Properties of Main-Chain Liquid Crystalline Polymers for Film Coextrusion

Enhancing the rheological properties of main-chain liquid crystalline polymers for film coextrusion

Zhenpeng Li, Paola A. Gonzalez Garza, Erica Baer, Christopher J. Ellison

McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712

Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106

Abstract

Liquid crystalline polymers (LCPs) possess much lower permeability than other conventional barrier materials such as polyethylene terephthalate (PET) and Nylon. It would be valuable to implement LCPs into film products by (co)extrusion, especially if the layers could be made very thin (i.e., less than 1 micron) to compensate for the expense of LCPs compared to conventional polymers. However, it is well known that the viscosities of LCPs are very low when compared to other conventional polymers; such low viscosities present a challenge in implementing LCPs into film extrusion. For example, multilayer coextrusion with other polymers requires the viscosity of two components to be closely matched in order to make high quality multilayer films. A new reactive extrusion method will be described for modifying the rheological properties of LCPs while not affecting their intrinsic liquid crystal structures. The rheological properties can be significantly enhanced (e.g., melt viscosity increased by roughly a factor of 20) and, most importantly, the modified LCPs were found to significantly improve the quality of LCP multilayer films made by coextrusion.