Barrier Properties of Thermotropic Liquid Crystalline Polymer Blends

Abstract

Oxygen barrier properties of poly(m-xylene adipamide) (MXD6) were enhanced by blending with different ratios of Vectra B950 (VB), a thermotropic liquid crystalline polymer. Blend sheets were prepared with extrusion without a compatibilizer, and the sheets were biaxially extended to form films. Thermal stability of the blends was improved with VB content. From the differential scanning calorimetry thermograms of the blends, it was concluded that the blends are incomaptible and crystallization occurred during extension. VB phases were spherical according to the scanning electron microscopy images of the samples. Tensile strength decrement with VB content was low compared with other non-compatibilized blend systems, which means that interfacial adhesion between MXD6 and VB phases exists. Oxygen permeability of the samples decreased with VB content. The results of unextended and extended samples fits well with the Maxwell model, which is a permeation model of composite consisting of spherical impermeable phases. Oxygen permeability of the extended films is lower than that of unextended sheets due to the enhanced barrier properties with elongation.