Glass fiber composites liquid crystalline polymers

Garcia M, Eguiazabal JI, Nazabal J (2003) Two scale reinforcement in hybrid composites based on poly (ether sulfone), glass fiber and liquid crystalline polymer. Compos Sci Technol 63... 

Another important application of thermoplastic fibers such as poly ether ether ketone (PEEK), Poly etherimide(PEI), and VectranM andHS (Vectranis the trade mark of Hoechst liquid crystalline polymer) is in making thermoplastic matrix composites. Commingled yams of the reinforcement and matrix such as quartz/PEEK, glass/PEI, Vectran HS/M are used to make the composites wherein the matrix yarn fuses to form the continuous phase of the composite. 

X.-B. Yu, C. Wei, and F.-A. Zhang. Studies on the mechanical and dynamic mechanical properties of thermotropic liquid crystalline polymer/unsaturated polyester/glass fiber in situ hybrid composites. Polym. Adv. Tech., 17 534-539, 2006. 

A fibril can be defined as a structural entity with material properties that are biased predominantly along a linear dimension or symmetry axis [51]. Such morphological entities are the reinforcing elements in MFCs. Furthermore, in contrast to the common short glass fiber reinforced composites or polymer-polymer composites where the reinforcement represents a liquid crystalline polymer, in the case of MFCs, flexible-chain polymers are used as reinforcement as emphasized above. 

A liquid crystalline polymer contains rigid rod like structure as discussed earlier which forms the hquid crystal phases. This rod like molecular conformations and chain stiffness give LCPs their most important self-reinforcing properties that are close to that of glass fiber reinforced composites. 

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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