Vectra resins

Entries 1-6 in Table I reveal an approximate constancy of volumetric CTE through the XYDAR 300, 400, and SRT-300 series resins. This result is not surprising, since the molecular structures of these materials are similar. However, the CTE values for a molded part reflect macroscopic structure (skin/core) as well as domain or molecular level morphology. The LCP molded part must therefore be regarded as a composite structure. These considerations as well as differences in basic molecular composition may explain the lower volumetric CTE for Vectra A-950 relative to the neat XYDAR resins, at least over the measured temperature range of 0-150 C. These factors may also be responsible for the lower anisotropy of the neat XYDAR 300 series resin. 

LCPs are finding use as replacement for epoxy and phenolic resins in electrical and electronic components, printed circuit boards (PCBs), and fiber optics. In these applications, the high mechanical properties, low coefficient of thermal expansion, inherent inflammability, good barrier properties, and ease of processing of LCPs (Vectra in particular) are important. 

The largest volume applieations of thermotropic LCPs is injection-molded parts. For injection-molding resins, the addition of fillers or fiber reinforced elements into neat LCP resins is utilized to lower cost and improve performace. Two of the noajor families of mesotropic LCPs on the market are Vectra fi om... 

Figure 11.18 shows commercial LCP tube made by Superex Polymer, Inc., from Vectra B-130, Zenite 6130, andXydar G-930 resins. Table 11.6 shows properties of the tubes. 

A history of the industrial development of thermotropic polymers would not be complete without a brief review of preceding technology, that is, the discoveries and developments made in lyotropic polymers. Thus, the timeline of milestones in liquid crystalline polymers proceeds from the initial observation of small molecule liquid crystallinity to the discovery of lyotropic and thermotropic high performance polymers and on through to the recent commercialization of thermotropic polyesters with the introduction of the Vectra (Celanese Corporation) and Xydar (Dartco Manufacturing) families of engineering resins. 

Specifically, Celanese has defined families of thermotropic polyesters derived from 2,6-naphthalene dicarboxylic acid (NOA), 2,6-dihydroxynaph-thalene (DHN) or 6-hydroxy-2-naphthoic acid (HNA). Indeed, the Vectra LCP engineering resins of Celanese Corporation are based on these monomers. 

In conclusion, the industrial development of thermotropic polyesters was traced through its theoretical origins, the identification of useful compositions, and ultimately to full commercialization of Xydar and Vectra, Commercialization of other thermotropic resins will, in all likelihood, be announced soon, as will high performance fibers made from variants of polymers described herein. 

Thermotropic aromatic copolyester fibers are produced by melt spinning since the combination of an aromatic backbone and flexible segments results in an LCP which can be melt processed. Copolyesters, such as p-hydroxybenzoic add (PHBA) modified poly(ethylene terephthalate) (PET), 60/40 PHBA/PET (X7G) polymers, have been produced by the Tennessee Eastman Company [425-427]. Other melt processable nematic thermotropic LCPs (TLCP), based on combinations of 2,6-naphthalene dicarboxylic add (NDA), 2,6-dihydroxynaphthalene (DHN) and 6-hydroxy-2-naphthoic acid (HNA), and referred to as Vectra LCP resins, have been conunercialized (trademark by Hoechst Celanese Corporation [406]). 

Coil formers, which carry windings in inductors, motors and transformers, must be tough and able to withstand the temperatures experienced. Polymers used include Vectra LCP, PBT, PC, PA and phenolic resins. 

Vectra. Liquid crystal polymer. Hoechst Celanese Corp. ViBRATHANE. PUR elastomer resin. UniRoyal, Inc. 

Figure 6.76 Dynamic coefficient of friction for various Celanese Vectra LCP resins (P = 6 N, v = 60 cm/min) [19].

The materials used in this study were LCP (Vectra A950, Ticona) and PET (Eastapak PET 7352, Eastman Chemical Company). Both resins were in pellet form and were dried at 120°C in a vacuum oven for 24 h before use. 

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