Thermotropic Liquid Crystal Polymer Reinforced Polyesters

Thermotropic Liquid Crystal Polymer Reinforced Polyesters 

Recently, the telecommunication industry has undergone rapid expansion, and a strong consumer trend towards smaller and lighter telecommunication devices, such as cellular phones and notebook computers, is indicated. Small connection sockets and chip earners are micro-injection-molded parts requiring the high flowability, high mechanical properties and dimensional stability of LCPs. These merits are now thought to be anodier application field for LCPs in the electronics industty. 

Modem Polyesters Chemistry and Technology of Polyesters and Copolyesters. 2003 John Wiley Sons, Ltd ISBN 0-471-49856-4 

This article is an overview of tire novel technology of self-reinforced LCPs with polyesters, poly(etiiylene terephtlialate) (PET) and poly(ethylene naphtha-late) (PEN) [10-13, 21, 23]. LCP/polyester blends in a polyester matrix form in situ fibrils which improve tire mechanical properties. LCPs have an inlierently low melt viscosity, and provide LCP/polyester blends that effectively lower the melt viscosity during melt spinning [24], and fast injection-molding cycles. The miscibility between tire LCP and polyesters can be controlled by the degree of transesterification [25] in tire reactive extrusion step, and fibril formation in LCP-reinforced polyester fibers has been studied. 

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Thermotropic Liquid Crystal Polymer Reinforced Polyesters... 

Meng YZ, Tjong SC, Hay AS. Morphology, rheological and thermal properties of the melt blends of poly(phthalazinone ether ketone sulfone) with liquid crystalline copolyester. Polymer 1998 39 1845-50. Kim JY, Kang SW, Kim SH. Thermotropic liquid crystal polymer reinforced poly(butylene terephthalate) composites to improve heat distortion temperature and mechanical properties. Fibers Polym 2006 7 358-66. Kim JY, Kim SH. Structure and property relationship of thermotropic liquid crystal polymer and polyester composite fibers. J Appl Polym Sci 2006 99 2211-9. 

These thermotropic liquid-crystalhne polymers have high melting points but can be melt-processed like other thermoplastics. The macroscopic orientation of the extended-chain crystals depends on the orientation imparted by flow during processing (molding, extrusion, etc.). Because of the fibrous nature of the extended-chain crystals, these plastics behave as self-reinforced composites, with excellent mechanical properties, at least in the chain direction. This is illustrated in Table 4.3 for molded specimens of a hquid-crystalline copolyester of ethylene glycol, terephthalic acid, and / -hydroxybenzoic acid [14]. In the direction parallel to the flow, the properties listed in Table 4.3 favorably compare with ordinary crystalline thermoplastics (nylons, polyesters) reinforced with up to 30% glass fibers. 

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