Abstract: Semi-aromatic copolyamides and copolyester-amides are obtained by placing an aliphatic polyamide into contact with an aromatic hydroxyacid or aminoacid, by operating at high temperature, under melting conditions, possibly in the presence of a catalyst, with a ratio of the monomer units of aliphatic polyamide to the mols of aromatic hydroxyacid or aminoacid comprised within the range of from 20:1 to 1:1.The semiaromatic copolyamides and copolyester-amides so obtained can display a thermotropic liquid-crystal behavior as a function of their content of aromatic units linked inside the molecular chain. Their elastic modulus results to be improved relatively to the alifatic polyamides used as the starting product, and the elongation at break results to be decreased.Such semiaromatic polyamides and copolyester-amides can find application in the production of high-stiffness articles, by means of moulding or extrusion processes.

Abstract: A thermotropic copolyester, showing a liquid-crystalline structure of nematic type within a desired temperature range, contains umits deriving from:(a) a saturated bicarboxy aliphatic acid;(b) 4,4'-di-hydroxy-diphenyl,(c) 4-hydroxybenzoic acid; and(d) 4-hydroxy-benzoic acid bearing an alkyl substituent or a halogen atom bonded to the aromatic ring.Such a copolyester constitutes a material endowed with self-reinforcing characteristics, originating, through the usual transformation processes by injection or by extrusion techniques, marked molecular orientations, which supply the manufactured articles with high stiffness characteristics.Said material can be also used as a reinforcing agent when is mixed, by means of the usual techniques, with the traditional thermoplastic polymers.

Abstract: Semi-aromatic copolyamides and copolyester-amides are obtained by placing an aliphatic polyamide into contact with an aromatic hydroxyacid or aminoacid, by operating at high temperature, under melting conditions, possibly in the presence of a catalyst, with a ratio of the monomer units of aliphatic polyamide to the mols of aromatic hydroxyacid or aminoacid comprised within the range of from 20:1 to 1:1.The semiaromatic copolyamides and copolyester-amides so obtained can display a thermotropic liquid-crystal behaviour as a function of their content of aromatic units linked inside the molecular chain. Their elastic modulus results to be improved relatively to the alifatic polyamides used as the starting product, and the elongation at break results to be decreased.Such semiaromatic polyamides and copolyester-amides can find application in the production of high-stiffness articles, by means of moulding or extrusion processes.

Abstract: A thermotropic copolyester, showing a liquid-crystalline structure of nematic type within a desired temperature range, contains units deriving from:(a) a saturated bicarboxy aliphatic acid;(b) 4,4'-di-hydroxydipheryl;(c) 4-hydroxybenzoic acid; and(d) 4-hydroxy-benzoic acid bearing an alkyl substituent or a halogen atom bonded to the aromatic ring.Such a copolyester constitutes a material endowed with self-reinforcing characteristics, originating, through the usual transformation processes by injection or by extrusion techniques, marked molecular orientations, which supply the manufactured articles with high stiffness characteristics.Said material can be also used as a reinforcing agent when is mixed, by means of the usual techniques, with the traditional thermoplastic polymers.

Abstract: A thermotropic copolyester, having a liquid-crystallne mesophase of nematic structure within a desired range of temperatures, contains units derived from:(a) a saturated aliphatic bicarboxy acid;(b) 4,4'-dihydroxy-biphenyl;(c) p-hydroxybenzoic acid; and(d) 2,6-hydroxynaphthoic acid.Such a thermotropic copolyester displays improved characteristics, in particular as regards its extensional modulus and its tensile strength, when is used as a self-reinforced material, or as a reinforcer material for traditional thermoplastic polymers.

Abstract: A thermotropic copolyester, having a nematic structure of the liquid-crystalline phase within a desired range of mesophase temperature, contains units derived from a saturated aliphatic dicarboxylic acid, 4,4'-dihydroxy-biphenyl and p-hydroxybenzoic acid, in a mutual ratio of from 1:1:0.5 to 1:1:8.This thermotropic copolyester is produced by copolymerizing in the molten state a saturated aliphatic dicarboxylic acid, 4,4'-diacyloxybiphenyl and p-acyloxybenzoic acid.The use is disclosed of the thermotropic copolyester as a self-reinforced material, and as a reinforcer material for such traditional thermoplastic polymers as polybutylene terephthalate, polyethylene terephthalate, polycarbonate and nylon.