Chemical resistance, liquid crystal polymers

Chemical Resistance of LGPs. Ceitain liquid crystal polymers (eg, Vectra) have extremely high chemical resistance to a variety of aggressive chemicals and solvents. Table 18 shows the chemical stabiUty of Vectra test-bars to various agents (244). 

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. 

Liquid Crystal Polymers Thermoplastic aromatic copolyesters with highly ordered structure. Has good tensile and flexural properties at high temperatures, chemical, radiation and fire resistance, and weatherabil-ity. Processed by sintering and injection molding. Used to substitute ceramics and metals in electrical components, electronics, chemical apparatus, and aerospace and auto parts. Also called LCP. 

Liquid crystal polymers (LCP) are highly ordered crystalline aromatic polyesters with high mechanical strength. They are exceptionally inert, having very high thermal and chemical stability, are highly resistant to UV radiation and are inherently flame retardant and antistatic. 

Liquid crystal polymers offer great dimensional stability in small, precision gears. It tolerates temperatures to 220 °C and has high chemical resistance and low mould shrinkage. It has been moulded to tooth thicknesses of about 0.066 mm. 

LCP materials are known for their high temperature resistance, particularly heat-distortion temperature (170-350°C). They also have excellent mechanical properties, especially in the flow direction. However, they have poor abrasion resistance, because of the oriented nature of the polymer chains. Liquid crystal polymers are used in automotive, electrical, chemical processing, and household applications. One application is for oven and microwave cookware. 

Interest, academic and Industrial, In Liquid Crystal Polymers (LCP s) was sparked by the commercialization of Kevlar aromatic polyamide fiber In the early 1970 s. [1,2] This fiber can be made almost as stiff and as strong as steel, at one fifth of the density of steel. In addition. It has good resistance to chemical attack and outstanding resistance to heat. From a scientific point of view, LCP s are Interesting because they. In addition to displaying a variety of phenomena and properties seen with conventional Isotropic polymers, also exhibit many of the complex physical properties of small molecule liquid crystals.[3]... 

Commercially available liquid crystal polymers (LCPs) (e.g., Vectra and Kevlar) exhibit excellent chemical resistance, low flammability, high elastic modulus, and low expansivity (depending on the mainchain orientation... 

Many high-performance polymer fibres are used in filter media to meet various specific requirements in diverse filtration applications. Filters made from fluoropol-ymer (Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), and Per-fluoroalkoxy alkane (PFA)) fibres, and membranes have inherent, chemical-resistant, and flame-retardant properties, and they are widely employed to filter aggressive chemicals and acids in the manufacture of wafers and microchips in the microelectronics industry. Ethylene ChloroTriFluoroEthylene (E-CTFE) melt blown fabrics have a unique ability to coalesce difficult liquids and can withstand the piranha effect in filtering ozone enriched ultrapure water. Polyphenylene sulfide (PPS) fibres are also chemical resistant, stand high temperature, and are suitable for making baghouse filters. Eilter media made from other high-performance polymer fibres, such as polyamide-imide, polyetherimide (PEI), Polyimide P84 fibre,polyetheretherke-tone, and liquid crystal polymers also appear in the filtration and separation market. 

Liquid crystal polymers have been replacing metal in medical devices. LCPs reduce weight and permit completely new equipment design concepts that are not easily achievable with conventional materials. Also, their excellent chemical resistance at high temperatures means that they are ideally suitable for repeated sterilisation. 

Liquid crystal polymers (also called aromatic copolyesters) have outstanding mechanical properties at both ambient and extreme temperatures. They are also highly resistant to many chemicals and so are used for many automotive under-bonnet and aerospace applications. A number of filled and reinforced grades are available and this material can be processed with very short cycle times. 

Liquid crystal polymer materials offer many advantages over conventional thermoplastics in injection moulding, including low mould shrinkage, minimum warpage and distortion, fast cycle time, ability to mould thin parts, low moisture absorption, and excellent chemical resistance. The mechanical properties are comparable to those of materials filled with short glass fibres. 

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