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Liquid Crystal Polymer (liquid + crystal_polymer)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Synergistic Ordering of Side-Group Liquid Crystal Polymer and Small Molecule Liquid Crystal: Order and Phase Behavior of Nematic Polymer Solutions,

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19-20 2007
Neal R. Scruggs
Abstract Addition of a small-molecule liquid crystal (5CB) to a cyanobiphenyl-based side-group liquid crystal polymer (SGLCP) stabilizes nematic order, increasing the isotropization temperature (TNI) more than 15,°C. Despite synergistic ordering at high concentration, small amounts of polymer destabilize nematic order. Even though TNI(SGLCP) is 27,°C greater than TNI(5CB), 2H NMR shows that the order parameter of the SGLCP is less than that of 5CB at concentrations for which monodomains were accessible (,10 wt.-%). The results imply that nematic order is frustrated in the bulk polymer and addition of small molecule LC relaxes this frustration by allowing greater configurational freedom. Conversely, adding small amounts of polymer to the bulk 5CB introduces frustration, resulting in the strong asymmetry of the phase diagram. [source]

Self-reinforced polypropylene/LCP prepregs and laminates

POLYMER COMPOSITES, Issue 5 2002
Y. C. Liang
Polypropylenes (PPs) of various molecular weights were mixed with a thermotropic liquid crystal polymer (LCP) to prepare unidirectional sheets (prepregs), quasi-isotropic and unidirectional laminates. The mechanical properties and the morphology of the prepregs and the laminates at 0° and 90° with respect to the machine direction were investigated as a function of draw ratio, LCP concentration and molecular weight of the PP. The results for prepregs and laminates showed that both drawing and LCP concentration generally enhanced modulus and tensile strength in machine direction. The morphology of LCP changed from spherical or ellipsoidal droplets to elongated fibrils as the draw ratio increased. The diameter of LCP fibrils decreased with increasing molecular weight of the PP matrix, indicating more effective droplet breakup and better mixing in the case of high molecular weight PP. [source]

Thermotropic liquid crystal polymer fabric reinforced polyimide composite materials

POLYMER COMPOSITES, Issue 5 2000
Asst. Prof. Seong Hun Kim Ph.D
An aromatic copolyeste thermotropic liquid crystal polymer (LCP) fabric was used to reinforce a polyimide (PI) matrix to produce composites. The LCP/PI composite was made to eliminate directional difference in the mechanical properties of LCP by controlling the individual reinforcement fabric alignment in different directions without losing any mechanical properties. As a result, a transversely isotropic LCP composite material could be obtained from the highly anisotropic LCP fiber. Interfacial adhesion between the LCP and polyimide was greatly improved by a NH3/H2 plasma treatment on the LCP fabric, thereby the significantly improving mechanical properties of the composite. Moreover, inter-laminar shear strength of the LCP/PI composite was further increased after heat treatment at 220°C for 1 hour. The LCP/polyimide composite retains stable mechanical properties up to 250°C. [source]