Dimensional stability, liquid crystal polymers

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. 

Polymerization of LB films, or deposition of LB films on polymers, offers the opportunity to impart to LB films a higher degree of mechanical integrity. However, preliminary work in this direction shows a conflict between the chainlike primary structure of the polymer and the well-organized supramo-lecular structure [15]. One possible solution may be the insertion of flexible spacers between the main chain polymer and the side chain amphiphile, a route also employed in liquid crystal polymers. These materials belong to an interesting class of two-dimensional polymers, of which there are few examples. These toughening techniques may eventually be applied to stabilize other self-assembled microstructures, such as vesicles, membranes, and microemulsions. 

Liquid crystal polymers (LCP) provide excellent strength, stiffness, dimensional stability and creep resistance. They are not damaged by the high temperatures commonly... 

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. 

In the automotive sector, engineering polymers such as polybutylene terephthalate (PBT) are replacing polyamide in some car electrical components because of their improved dimensional stability. Also, with the ever increasing temperature requirements in under-bonnet applications, liquid crystal polymer (TCP) and polyphenylene sulfide (PPS) have also been replacing polyamide [1]. 

The matrix material used for this project was Ticona s Vectra A950RX liquid crystal polymer (LCP), which is a highly ordered thermoplastic copolymer consisting of 73 mol% hydroxybenzoic acid (HBA) and 27 mol% hydroxyn hthoic acid (HNA). This LCP has the properties need for bipolar plates, namely high dimensional stability up 250"C, extremely short molding times (often 5-10 s), exceptional dimensional... 

The section commences with monosubstituted ferrocene derivatives, after which the influence of the substitution pattern on the formation and stability of liquid-crystalline phases for disub-stituted ferrocene derivatives will be discussed. Next, the influence of the three-dimensional structure of ferrocene on the mesomorphic properties will be highlighted, optically active ferrocene materials will be described and, finally, ferrocene-containing liquid-crystalline dendrimers will be introduced ferrocene-containing liquid-crystalline polymers will not be reported. Note that a review devoted to ferrocene-containing thermotropic liquid crystals has already been published. ... 

Note that the threshold field here is smaller than the threshold field of the Freedericksz transition in the regular liquid crystal cell consisting of two parallel substrates with the same cell gap, for the following reason. In the regular cell the hquid crystal is anchored by the two-dimensional surface of the substrate, while in the polymer-stabilized hquid crystal cell here, the liquid crystal is anchored by the one-dimensional polymer fiber. 

---