Liquid-crystalline polyamide-amorphous

Acid anhydrides, 391 Amino hydrochloride water solutions, lyotropic phases, 306-308,310/ Amorphous polyimide-liquid-crystalline polyamide composites. See Liquid-crystalline polyamide-amorphous polyimide composites Amphiphilic liquid crystal(s), establishment, 235,236/... 

Molecular Composites of Liquid-Crystalline Polyamides and Amorphous Polyimides... 

In this article, the synthesis, characterization, rheology, solution processing, and mechanical properties of novel molecular composites are discussed. These molecular composite are block copolymers composed of a liquid-crystalline polyamide and two amorphous polyimides. Also, the rheological properties of both isotorpic and anisotropic solutions of PBTA homopolymers and PBTA/PI block copolymers are... 

Similar copolyimide was prepared using 3,7-diamino-2,8(6)-dimethyldibenzothiopheneS,5-dioxide (DDBT) instead of m-SED and its performance for olefin/paraffm separation was investigated [74]. Block copolymers of liquid crystalline polyamide and amorphous PI were prepared from a two-pot polycondensation reaetions [75]. Hydrocarbon (C-2 and C-3) separations in copolyimide dense membranes derived from 6FDA, DDA and 1,5-naphthalene diamine (NDA) was studied [76]. Gas transport properties of 6FDA, DDA and 3, 3 -diaminodiphenyl sulfone (DIDS) was reported [77]. 

Even within a particular class of polymers made by step-growth polymerization, monomer composition can be varied to produce a wide range of polymer properties. For example, polyesters and polyamides can be low-Tg, amorphous materials or high-Tg, liquid crystalline materials depending on the monomer composition. 

The use of other materials as the central layer of the barrier laminate is, of course, feasible. Obvious candidates for this application include the high barrier amorphous polyamides (Chapter 5 (50)) and the liquid crystalline polyesters (Chapter 3(57)) which either develop slightly improved barriers under elevated relative humidity conditions or at least do not lose barrier properties. No reports are yet available concerning the performance of such structures. 

Linear, aromatic polyamides (PARA) are either liquid crystalline, semicrystalline, or amorphous. Mainly the latter resins are used in blends with PP, viz. PARA with PP-MA [Iwanami et al.,... 

However, in addition to the three phases indicated above, there are interphase zones which may contribute significantly to the gas permeation. The interphases that connect the crystalline PA phase to the amorphous PA phase and to the molten polyether phase could behave as a quasi-crystalline phase, or as a liquid-like phase. In polyethylenes, the constraints due to the crystallites reduce the molecular diffusion, and make it more selective [32]. In a recent study, we pointed out the significant contribution of these constrained interphases to the permeation in nanocomposite materials with a semi-crystalline polyamide 12 matrix [33]. Although the existence of such an interphase can be hardly proven, the result analysis based on the idea of coexistence of two amorphous fractions ( real ... 

Linear, aromatic polyamides (PARA) are either liquid crystalline, semicrystalline, or amorphous. Mainly the latter resins are used in blends with PP, viz., PARA with PP-MA (Iwanami et al. 1990), PARA with PE-MA, or PP and hydrazine (Yoshihara 1990). Blends of copolyphthalamide (PPA) with PP were compatibihzed using either PP-MA (Paschke et al. 1993, 1994) or PP grafted with acrylic acid (Brooks et al. 1993, 1994). 

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)...

It is significant that the reinforcement degree corresponds to a class of polymer forming a nanocomposites matrix. The largest values of / are obtained for polymers whose chains are able to stretch on the silicate platelet surface (rigid-chain polyimide, crystallising polypropylene and thermotropic liquid crystalline polyester), intermediate values for polymers whose chains are able to stretch only partly (polycarbonate, poly (butylenes terephthalate) and amorphous polyamide-6) and the smallest values for nanocomposites on the basis of epoxy polymer, the capability of chains stretching of which decreases sharply because of the availability of transverse covalent bonds network [30]. 

Most polymers fall in the class of translucent resins. These include acetal, polyamide, polybutylene terephthalate (PBT), polyethylene, and polypropylene as examples. There are very few neat polymers that are truly opaque (this depends on thickness as well). Liquid crystal polymer (LCP) is an example of a typically opaque polymer. It is theorized that these semicrystalline and crystalline resins will scatter some portion of incident light due to spherulitic crystal structure and the amorphous-crystalline region interfaces themselves. 

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