Abstract: An aqueous dispersion of an aromatic polyethersulphone of sole repeat unit ##STR1## and having mean particle size below 25 .mu.m, preferably below 12 .mu.m, is prepared by (1) stirring the polyethersulphone in methylene chloride to form a solution and then a coarse particulate solid, (2) adding further methylene chloride to form a slurry, (3) milling the slurry to form a dispersion, (4) mixing a methylene chloride - and water-miscible liquid which does not swell the polyethersulphone with the milled dispersion, (5) filtering the dispersion and washing the wet cake with the liquid and then water, and (6) dispersing the wet cake in water, optionally with milling, to provide the aqueous dispersion.

Abstract: Block copolymers are prepared by heating at above 250.degree. C. (i) a halophenate, (ii) dihalobenzenoid compound plus bisphenate, and/or (iii) a polymer formed from (i) or (ii) having at least one phenate end group, said halophenate and/or dihalobenzenoid compound containing SO.sub.2 groups ortho or para to the halogen atoms, in the presence of a suspension of a crystalline polyetherketone or etherketone/sulphone copolymer.

Abstract: A method of coating a substrate surface, which method comprises: (a) applying a primer composition to the substrate surface which primer composition comprises thermoplastic polymer material dispersed in an inert liquid diluent, at least 50% by weight of said theroplastic polymeric material being constituted by at least one thermoplastic aromatic polyethersulphone; (b) before the applied primer composition has become touch-dry, applying a dispersion of a tetrafluoroethylene polymer top-coat material in an inert liquid diluent over the coated substrate; and (c) removing the inert liquid diluent or diluents and sintering the combined coating of the primer and top-coat layers. The primer compositions do not in the claimed method, need to be dried and baked to exert an effective priming action.