Microconfinement effect on gas barrier and mechanical properties of multilayer rigid/soft thermoplastic polyurethane films

Abstract

ABSTRACT In this article, rigid/soft thermoplastic polyurethane (TPU) films were produced via layer‐multiplying co‐extrusion and the effect of confinement on morphology and gas barrier and mechanical properties is studied. The soft TPU, which is 52% hard‐segment, shows phase separation, while the rigid, 100% hard‐segment TPU exhibits amorphous structures. Even though the viscosity ratio of the two TPUs is over 10 and the elasticity ratio around 100, optical and atomic force microscopies show that a multilayer structure was successfully achieved. Then, the multilayer TPU films were uni‐axially stretched to different amounts of deformations, from 0% to 300%. DSC and WAXS results show that microconfinement occurs during orientation, which causes a significant reduction in oxygen permeability of multilayer TPU films, when stretched at 75%, by comparison to the mono and bi‐layer TPU. The dependence of gas barrier properties on temperature and deformation was also investigated, and a 100% improvement in elongation at break was found when compared to films of the rigid TPU. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 41849.