Abstract: A polymer capable of forming an anisotropic melt characterized in that the polymer chain includes residues of cross-linking reactants at a concentration sufficient to give a polymer with a melt viscosity of not greater than 10.sup.7 Nsec/m.sup.2 measured by capillary rheometry at a shear rate of 10.sup.4 N/m.sup.2. The polymers exhibit favorable shear dependent viscosity characteristics in that the viscosity is high under low shear conditions and is low under high shear conditions, as judged by the viscosity characteristics of polymers of the same composition but not containing the residues of cross-linking reactants.

Abstract: A melt-fabricatable or melt-fabricated composition comprising (i) a crystalline thermoplastic aromatic polyetherketone containing the repeat unit ##STR1## alone or in conjunction with other repeat units said polymer having an inherent viscosity of at least 0.7 and (ii) a glass and/or carbon fibre reinforcing agent, which composition is melt-fabricatable into a composition exhibiting, or alternatively (if melt-fabricated) exhibits, an increase in heat deflection temperature (HDT) of at least 3.degree. C. per 1% by weight of reinforcing agent above the HDT of the unreinforced polyetherketone and an increase in flexural modulus of at least 0.2 GN.sub.m.sup.-2 per 1% by weight of reinforcing agent above the flexural modulus of the unreinforced polyetherketone.

Abstract: A method for the production of thermoplastic polyester compositions comprising mixing a normally flammable thermoplastic polyester, preferably containing at least 80% by weight of repeating units of ethylene terephthalate, tetramethylene, terephthalate or ethylene-1:2-diphenoxyethane-4,4'-dicarboxylate units, an effective amount of fire-retardant additives and an aqueous colloidal dispersion of PTFE, subjecting the mixture to conditions under which the polyester becomes molten and removing volatile materials from the melt.