Morphology and mechanical properties of fibers from blends of a liquid crystalline polymer and poly(ethylene terephthalate)

Abstract

AbstractThe domain morphology and mechanical properties of fibers spun from blends of a thermotropic liquid crystalline polymer, Vectra A‐900, and poly(ethylene terephthalate) (PET) have been studied across the entire composition range. The PET phase was removed by etching to reveal fibrillar LCP domains in the blends of all compositions. The 0.5μm fibril appeared to be the basic structural entity of the LCP domains. A primary effect of composition was the change from discontinuous fibrils when the composition was 35 and 60% by weight LCP to continuous fibrils when the composition was 85 and 96% LCP. This transition had major ramifications on the mechanical properties: the modulus increased abruptly between 60 and 85% LCP, and a change in the fracture mode from brittle fracture to a splitting mode was accompanied by an increase in fracture strength. Different models were required to describe the mechanical properties of the discontinuous and continuous fibril morphologies. Analytic models for short aligned fibers of Nielsen, and Kelly and Tyson were applicable when the LCP fibrils were discontinuous, while modulus and strength of blend fibers with continuous LCP fibrils were discribed by the rule of mixtures.