Rheology, morphology and properties of LCP/nylon 66 composite fibers

Abstract

The rheology, morphology and properties of the composite systems of LCP, Vectra A 950 and Nylon 66 were investigated. The viscosity ratio of LCP and matrix has strong influence on their morphology. For LCP blends, the viscosity ratio of LCP is a critical factor in determining the blend morphology. The optical micrographs show that the good fibrillation can be achieved when the viscosity of the dispersed LCP phase is less than that of the Nylon 66 matrix at 310°C. The dispersed LCP domains tend to be spherical or cluster-like when the viscosity ratio of the dispersed LCP phase and the Nylon 66 matrix is more than 1 at 280°C. The scanning electron microscopy (SEM) and optical micrograph observations show that Nylon 66 is immiscible with LCP, and there are two distinct phases in the blends. The morphology of LCP phase changes with the composition. LCP exhibits a fine fibril dispersed phase in the Nylon 66 matrix in the low LCP concentration. With an increase in LCP concentration, the morphology of LCP phase is changed from a fine fibril dispersed phase to a perfectly aligned continuous fiber reinforced phase in the rich LCP concentration. The tensile moduli increase with LCP concentration, especially in the rich LCP concentration. The tensile strength increase with LCP concentration only when LCP concentration is above 40 wt%. Compared to the pure Nylon 66 fiber, the 40 wt% LCP composite sample shows a 982.1% increase in tensile modulus and a 123.3% increase in tensile strength. The mechanical properties of composite fibers are below the rule of mixtures if the LCP concentration is low, but above the rule of mixtures if the LCP concentration is high.