Abstract: The present invention provides block copolymers of the formula: ##STR1## in which R represents an aliphatic residue, A an aromatic residue, x is such that the inherent viscosity (measured in methanesulphonic acid at a concentration of 0.2 g per deciliter at 30.degree. C.) in deciliters per gram is greater than 0.6, and n and n' are greater than or equal to 2. These polymers are made from two different diacids and have two glass transition temperatures, with one glass transition temperature being between -50.degree. and +50.degree. C. and the other glass transition temperature being between 180.degree. and 300.degree. C.

Abstract: The present invention relates to new polyamides comprising, on a mass basis:(a) 45 to 75% of an x,T unit, x being between 4 and 12 inclusive, the x,T unit being the condensation product of a diamine having x carbon atoms and of terephthalic acid, and(b) 55 to 25% of an aliphatic unit -HN-(CH.sub.2).sub.n -CO, n being between 6 and 14 inclusive. and the terpolyamides obtained by including a monomeric unit (c) such as the unit 6 or 6,I as a replacement for part of the aliphatic unit (b).The polyamide compositions thus obtained exhibit a Tg lower than 130.degree. C., a Tm higher than 230.degree. C. and a good crystallizability.

Abstract: Copolyamides having high crystallinity over the whole composition range, a melting enthalpy .DELTA.H>3.5 cal/g and a melting point T.sub.M higher than 270.degree. C. and articles manufactured therefrom are disclosed, said copolyamides comprising, by moles:a) 1 to 99% of a unit A of formula--(NH--R--NHCO--AR.sub.1 --CO)--in which R is a --(CH.sub.2).sub.n --carbon chain where n is coma) between 4 and 20, and AR.sub.1 is the residue from the condensation of terephthalic acid and/or of the diester form thereof; andb) 99 to 1% of a unit B of formula--(NH--R--NHCO--AR.sub.2 --CO)--in which R is the same carbon chain as in unit A and AR.sub.2 is the residue from condensation of naphthalene-2,6-dicarboxylic acid and/or the diester form thereof.

Abstract: A process for the manufacture of polyamides consisting essentially of the stages of:(i) reacting 10 to 90% by weight of the aliphatic and/or cycloaliphatic and/or aromatic-aliphatic diamines (c) with a lactam and/or corresponding amino acid (a) or the substantially stoichiometric combination of one or more aliphatic diamine(s) and of one or more dicarboxylic aliphatic acid(s) and with the aromatic diacid (b); and(ii) reacting the remainder of the aliphatic and/or cycloaliphatic and/or aromatic-aliphatic diamine (c) with the oligomer produced in stage (i) in one or more substages.