Vectra liquid crystalline polymer

Precision parts, electric connectors Vectra Zylon Twaron Liquid crystalline polymers DuPont, USA Toyobo, Japan Akzo, Netherlands... 

The concentration of Vectra in the blend also shows a pronounced effect on the drawability and the modulus of the Ultem/Vectra blend sheets. Under the same extrusion conditions, the drawability, as characterized by the maximum draw ratio, decreased with increasing content of the liquid crystalline polymer in the blend. However, when the draw ratio is similar the higher the content of the reinforcing phase, the higher the torsional modulus. The highest value of the torsional modulus was obtained for the materials with only 10 X Vectra because of the higher drawability of the system. 

To date, reports of investigations on the gas transport properties of main chain liquid crystalline polymers appear to have been limited to the work conducted in our laboratory. Chiou and Paul (4.) have briefly described the transport parameters of an extruded film of an LCP having a similar structure to the commercial product Vectra. This copolyester belongs to the family of napthylene thermotropic polymers (NTP s) commercialized by Hoechst-Celanese Corp. whose synthesis and properties have been described previously (iLS.). Transient permeation experiments were conducted with a series of gases. The effective... 

Table 2. Comparison of Gas Transport Properties of a Wholly Aromatic Liquid Crystalline Polymer (Vectra type) with Polyacrylonitrile at 35 C...

Gopakumar et al. [10] reported the in situ compatibilization of poly(phenylene sulfide) (PPS)/wholly aromatic thermotropic liquid crystalline polymer (TLCP) Vectra A950 blends by reactive extrusion. The authors prepared the in situ compatibilized PPS/TLCP blends in a twin-screw extruder by reactive blending of PPS and TLCP in the presence of dicarboxyl-terminated poly(phenylene sulfide) (DCTPPS). Block copolymer was formed during reactive blending, by transesterification reaction between carboxyl... 

Vectra A is a commercially available polymer from Hoechst-Celanese. It is a random co-polyester of hydroxy benzoic acid (HBA) and hydroxy napthoic acid (HNA), which is a well-known class of thermotropic liquid crystalline polymer (TLCP) [92-95]. Crystallization of molecules of TLCPs is considerably different from that of polymers like polyethylene or polyethylene terphthalate [1], TLCPs have reduced flexibility compared to the latter, which implies that large translations of their molecules are required for recrystallization [96-99],... 

X. Jin and T. S. Chung, Thermal decomposition behavior of main-chain thermotropic liquid crystalline polymers, Vectra A-950, B-950, and Xydar SRT-900, Journal of Applied Polymer Science, 73, 2195 (1999). 

Three commercially available thermotropic liquid crystalline polymers (TLCPs) were presented as examples in this section. They are Hoechst Celanese Vectra A950 and Vectra B950 as well as Amoco Xydar . Vectra A950 is a random copolymer of 73 mol% 4-hydroxybenzoic acid and 27 mol% 6-hydroxy-2-naphthoic acid, and Vectra B950 is a random copolyesteramide consisting of 60 mol% of 6-hydroxy-2-naphthoic acid, 20 mol% terephthalic acid, and 20 mol% p-aminophenol. Xydar is made from p-hydroxybenzoic acid, isophthalic and/or terephthalic acids, and 4,4 -biphenol. The repeating unit structures of the three LCPs are shown in Figure 6.2. 

Bose, S. Mukherjee, M. Das, C. K., Silicone Rubber Compatibilized Syndiotac-tic Polystyrene and Thermotropic Liquid-Crystalline Polymer (Vectra A950) Blend. Polym. Plast. Technol. Eng. 2009,48,158-163. 

Use of Vectra A950 liquid crystal polymer is described with reference to the production of barrier packaging for the containment of anaesthetic emulsions. The pouches were compression moulded and sealed by thermal impulse welding. Concentrations of lidocaine and prolocaine in the emulsion were studied for 14 weeks at two different temperatures, 40 degrees C and 60 degrees C, and at 100% relative humidity. Loss of substances from the emulsion was due mainly to adsorption onto the polar surface of the liquid crystalline polymer, it is reported. 21 refs. 

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. 

The commercial polymers used in the study are characterized in Table 1. The polypropylenes PP1-PP5 were homopolymers exhibiting different melt viscosities (see Fig. 1) supplied by Neste Chemicals. Liquid-crystalline polymer 1 (LCPl) (Vectra A950 by Hoechst Celanese) is a totally aromatic polyester-type thermotropic main-chain LCP copolymer based on p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA). Liquid-crystalline polymer 2 (LCP2) (Rodrun LC-3000 by Unitika Ltd) is a more flexible thermotropic main-chain LCP copolyester consisting of 60%... 

Measurements of this type were undertaken simultaneously with the contact zone observations [37], and produced consistent values of ( n — 5(3/533) for a range of polymer fibres, namely polyethylene terephthalate, polyethylene and a thermotropic liquid crystalline polymer based on hydroxybenzoic and hydroxynaphthoic acid in the ratio 73 27 (Vectra). Values for El were in the range 1.94-2.34 GPa for polyethylene terephthalate, 0.63-1.50 GPa for polyethylene and 0.96-1.01 GP for Vectra. Typical contact zone observations are shown in Figure 8.13. 

The first melt-processable (later categorized as thermotropic liquid-crystalline) polymer, based on p-hydroxybenzoic acid and biphenol tereph-thalate, was reported by Steven Cottis in 1972. This polymer is now available on the market as Xydar . In 1973, the first well-characterized thermotropic polymer, a copolyester of p-hydroxybenzoic acid and ethylene terephthalate, was patented by Herbert Kuhfuss and W. Jerome Jackson (Eastman-Kodak Co., USA). They reported the discovery of liquid-crystalline behaviour in this polymer in 1976. At the beginning of the 1980s, the Celanese Company developed a family of processable thermotropic liquid crystalline polymers based on hydroxybenzoic acid and hydroxynaphthoic acid, later named Vectra . 

Figure 6.39 shows one of the important signatures of nematics, namely their low viscosity. Thermotropic liquid-crystalline polymers such as Vectra are of very low viscosity and complicated, tortuous moulds are readily filled. A generalized shear rate-viscosity curve for liquid-crystalline polymers (nematics) is shown in Fig. 6.40. Shear thinning occurs in both regions I and III. Some nematics only show parts of this curve.

The liquid-crystalline polymer component (Vectra) is oriented in the blends and possesses an approximately invariant thermal expansion coefficient anisotropy. 

Other interesting blends containing PE are natural rubber/PE, PP/UHMWPE, polyvinylidene fluoride (PVDE)/UHMWPE, PE/EVA, PE/PVC, PE/liquid crystalline polymer (Vectra), and styrene-isoprene-styrene block copolymers with ULDPE [12] with good puncture resistance (>100 kN/m). 

Figure6.22 Viscosity data on LCP(Vectra)/amorphous polyamide(Trogamid T) blends demonstrating the dramatic viscosity reduction with addition of liquid crystalline polymers to non-liquid crystalline polymers (reproduced (replotted) from Siegmann, A., Dagan, A. and Kenig, S., Po/ym. (1985) 26, p. 1325, with permission from Elsevier)...

The materials used in this study were poly (ethylene terephthalate) (Shell Cleartuf 7202C) with a 0.72 intrinsic viscosity, and a liquid crystalline polymer, produced by Ticona under the trade name Vectra A950. The LCP is a co-polyester of 73 mol% HBA (4-hydroxybenzoic acid) and 27 mol% HNA (6-hydroxy-2-naphthoic acid). 

Vectra based on aromatic polyesters (Calundann 1980) respectively. Molecular structure of aromatic polyester based liquid crystalline polymer, Vectra is represented in Fig. 13.1. 

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