POLYETHER-ETHERKETONE PEEK

This semi-crystalline polymer belongs to the family of polyether ketones, Tg= 145 C Tm = 235 C. Developed in 1980 by ICI, it is a superb engineering polymer, showing excellent mechanical properties that are retained at elevated temperatures. Due to its extremely high price, its utility is still limited to the field of aviation and space (reinforced with carbon fibers), electronics and machinery. Another advantage is its stability towards fire or chemicals, although it is sensitive to UV radiation. 

Liquid Crystal Polymers (LCP) This novel polymeric family excels in thermal and mechanical performance. The uniqueness of these polymers stems from the extraordinary crystalline stmcture, exhibiting ordered domains even in the liquid state. These are chainlike macromolecules of rigid structure, mainly because of the existence of aromatic rings such as aromatic polyamides and polyesters. There are two major groups—lyotropic and thermotropic. In the former group, the liquid crystals are formed in an appropriate solution, usually forming fibers (like Kevlar , that appeared in 1965 as an aramide). 

The thermotropic group consists of a crystalline liquid formed during cooling of a dry melt (similar to the processing of thermoplastics)—the first having been the aromatic polyesters (1972). When a disordered melt cools in a region of proper transition temperature (Tj), a liquid crystal phase (mesophase) is formed. It is characterized by high order (anisotropic) that creates turbidity. 

The most common form is the nematic, a bimdle of parallel, long, rodlike molecules. Additional cooling to the primary transition temperature, T leads to solidification into a solid crystalline phase (small crystallites). In the region between Tj and T , a liquid of very low viscosity prevails, in contrast to the high melt viscosity. The aromatic polyesters have high heat distortion temperatures (HDT). Vectra, composed of para-hydroxy-benzoic acid (PHBA) and para-hydroxy-naphtoic acid (PHNA), has an HDT of 180 C-240 C. Xy-dar, composed of PHBA, tera-phthalic acid and biphenol, has an even higher HDT of 260 C-350 C. 

Among other derivatives of cellulose are cellulose-acetate (CA) which appeared in 1927, ethyl-cellulose (1935), cellulose-acetate-butyrate (CAB) developed in 1938, and cellulose-acetate-propionate (CAP) developed in 1960. 

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The Bell/Boeing V22 Osprey tilt-rotor aircraft uses carbon fiber-reinforced polyether etherketone (PEEK) for doors and housings of the engine air particle separator and for fuel vent tanks (Figure 6.44). TP polyimide (TPI) forms the basis for an injection-molded spline adapter in the drive train which tilts the rotors. Costs were reduced some 22%. The parts were developed by RTP Company with Bell Helicopter and molder RAM Inc., Texas. The tanks are molded by the lost core process. 

The model material used is a unidirectional carbon fiber-reinforced, thermoplastic polyether-etherketone (PEEK) composite with fiber diameter of = 8 fim. The fiber orientations studied are shown in Figure 1. The mechanical properties of this material are listed in Table 1. The first principal material direction, indicated by 1 in Table 1, is parallel to the fiber direction (Figure 1), the second and the third one are perpendicular to the fiber orientation. The anisotropic composite material properties were specified using the rule of mixture type equations. ... 

UV detector. A small-diameter tube is placed in the side arm of the tee and runs to the inlet to the MS. The tubing is usually either PEEK (polyether-etherketone) or fused silica. A smaller-inner-diameter tube penetrates into the source and acts as a restrictor, limiting the flow through this side arm. The fluid pressure drops below the two-phase region somewhere in the transfer line. The small droplets of modifier formed clean the transfer line and rapidly delivers the solute to the MS source. 

Figure 1 Cost-related (specific) flexural strength of major thermoplastics, versus cost-related (specific) thermal tolerance. The unit cost is the market price in US cents (1992) of 1 cm plastics. The thermal tolerance is the temperature difference (AT) over room temperature (AT — T - room T), by which temperature (7 ) the flexural modulus is equal to 1 GPa. Designations, abbreviations WFRP-S, wood fiber reinforced PP (S type) of AECL, Canada (See Table 1) PMMA, polymethylmethacrylate PVC, pol)winyl chloride PS, polystyrene PP, polypropylene UP, unsaturated polyesters PA-GF, glass fiber (35%) reinforced polyamide PHR, phenolic resin EP, epoxy resin ABS, acrylonitrile/butadiene/styrene copolymer UF, urea/formaldehyde LDPE, low density polyethylene PC, polycarbonate POM, polyoxymethylene CAB, cellulose acetate butyrate LCP, liquid crystal polymers PEEK, polyether-etherketone PTFE, polytetrafluorethylene.

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