LCP

Gramercy, La. LCP Chemicals 181.4 1958 OxyTech HC3B, HC3C diaphragm 1... 

Du Pont s Zenite range of LCPs have been reintroduced. These materials are also LCP polyesters based on HBA copolymers with, it is beheved, various amounts of 4,4 -biphenol, terephthaUc acid, and naphthalene-2,6-dicatboxyhc acid (NDA) as comonomers. Their compositions are thus similar to those of XYDAR with added NDA to further reduce the melting point (235,236). 

Properties of Typical Commercial LCPs. Table 17 presents data on three significant, commercially available LCPs (238). Elongation values have been quoted for HX-2000 as 0.6%, for Xydar G-930 as 1.6%, and for Xydar G-540 as 1.5%. Eurther details can be obtained from the manufacturers. 

LGP Economics. LCPs are expensive materials. Prices in January 1996 (248) ranged from 15.20/kg for mineral-filled resin, 15.73— 23.43/kg for glass-fiHed resin, and up to 48.40/kg for unfilled extmsion-grade polymer. One of the basic reasons is the fundamental high cost of monomers and intermediates which is a consequence of low volume. 

A very high, price and performance family of polymers called liquid crystal polymers (LCPs) exhibit extremely high mechanical and thermal properties. As their ease of processing and price improve, they may find appHcation in thin-waH, high strength parts such as nails, bolts, and fasteners where metal parts cannot be used for reasons of conductivity, electromagnetic characteristics, or corrosion. 

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

Four companies (trade name in parentheses), Amoco (Xydar), Hoechst-Celanese (Vectra), Du Pont, and Granmont (Granlar), make thermotropic LCPs for various types of extmsion and mol ding processes. Six companies have discontinued TCP materials that were either commercial or under development. These companies include ICl, BASF, Eastman, Bayer, General Electric, and Monsanto. 

Many different combinations of carboxyflc acid and hydroxyl groups have been tested to form LCPs. An aromatic stmcture (ben2ene, naphthalene, anthracene, etc) is required that has its functional groups symetricaHy arranged on opposite sides of the molecule. Examples are a 1,4-substituted ben2ene compound or 2,6-substituted naphthalene compound. These monomers are often complex and expensive molecules and account for a significant portion... 

Liquid crystal polymers (LCP) are a recent arrival on the plastics materials scene. They have outstanding dimensional stability, high strength, stiffness, toughness and chemical resistance all combined with ease of processing. LCPs are based on thermoplastic aromatic polyesters and they have a highly ordered structure even in the molten state. When these materials are subjected to stress the molecular chains slide over one another but the ordered structure is retained. It is the retention of the highly crystalline structure which imparts the exceptional properties to LCPs. 

Another natural polymer that needs a fresh look into its structure and properties is bitumen [123], also called asphaltines, that are used in highway construction. Although a petroleum by-product, it is a naturally existing polymer. It primarily consists of polynuclear aromatic and cyclocaliphatic ring systems and possesses a lamellar-type structure. It is a potential material that requires more study, and high-performance materials such as liquid crystalline polymer (LCP) could be made from it. 

Materials with totally new property combinations may be achieved by blending two or more polymers together. Through blending of thermotropic main-chain LCPs with engineering thermoplastics, the highly ordered fibrous structure and good properties of LCPs can be transferred to the more flexible matrix polymer. LCPs are blended with thermoplastics mainly in order to reinforce the matrix polymer or to improve its dimensional stability, but LCP addition may modify several... 

Other properties of thermoplastics as well. Owing to the relatively low-melt viscosity of thermotropic LCPs, often a small amount of LCP decreases the blend viscosity significantly and renders the matrix thermoplastics easier to process [9-211. 

The blends of thermotropic LCPs and thermoplastics are generally two-phase systems where the dispersed LCP phase exists as small spheres or fibers within the thermoplastic matrix. Often a skin/core morphology is created with well-fibrillated and oriented LCP phases in the skin region and less-oriented or spherical LCP domains in the core. 

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