Wholly Aromatic Copolyester

The carboxy-ester interchange melt polyesterification used for the preparation of this wholly aromatic copolyester is followed by a solid-state postpolyesterification (Scheme 2.65). (Reprinted from ref. 439. Copyright 1990 John Wiley Sons, Inc., by permission of the copyright owner.)... 

Positron annihilation lifetime measurements of free volume in wholly aromatic copolyesters and blends . Marcromolecules. 28, 6100. 

A high-performance, wholly aromatic copolyester suitble for injection molding was commercial introduced in late 1984 by Dartco Manufacturing under the trade name Xydar. Xydar injection-molding resins are based on terephthalic acid, p,p -dihydroxybiphenyl, and p-hydroxybenzoic acid. 

The wholly aromatic copolyester is reported to have outstanding thermal oxidative stability, with a decomposition temperature in air of 1040 F (560°C) and 1053°F (567°C) in a nitrogen atmosphere. The resin is inherently flame retardant and does not sustain combustion. Its oxygen index is 42, and smoke generation is extremely low. 

The wholly aromatic copolyester for injection molding is available in filled and unfilled grades. It can be molded into thin-wall components at high speeds. The high melt flow also enables it to be molded into heavy-wall parts. No mold release is required because of the inherent lubricity and nonstick properties. No post-curing is necessary because the material is completely thermoplastic in nature. The material is expected to have many applications because of its moldability and its resistance to high temperatures, fire, and chemicals. 

Xydar Dartco Mfg. Wholly aromatic copolyester injectionmolding resin... 

Even higher glass transition temperatures are achievable if4,4 -functionalized 1,1 -binaphthyl monomers are used [28 b, 30]. For example, the homopolyester derived from 4,4 -dihydrox-1,1 -binaphthyl (BDP) and phenylterephthalic acid with an inherent viscosity of 1.90 dl/g has a Tg of 183 °C. The polyester is nematic up to its decomposition temperature and forms a nematic glass below Tg. In a similar homopolyester based on 4,4 -dicarboxy-1,1 -binaphthyl and t-butyl-hydroquinone the Tg was found to be 189 °C. In both cases, good solubility in common chlorinated solvents is maintained. This type of monomers was, for example, also used to modify wholly aromatic copolyesters based on 6-hydroxy-2-naphthoic acid (HNA) and 2,6-naphthalene dicarbox-ylic acid (NDA) [25 a]. 

McCullagh, C. M., Yu, Z., Jamieson, A. M., Blackwell, J., and McGervey, J. D., Positron annihilation lifetime measurements of free volume in wholly-aromatic copolyesters and blends. Macromolecules, 28, 6100-6107 (1995). 

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