A polymer composition comprises at least one thermoplastic polymer selected from the group formed by polyetherimides and polysulphones, at least one epoxy resin modified by at least one aromatic polyamine, and at least one other thermoplastic selected from the group consisting of a polyphenylene ether, a polyphenylene sulfide and an aromatic polyether. The epoxy resin is formed from at least one polyepoxide containing at least 2 epoxy groups in its molecule and the aromatic polyamine contains at least two primary amine groups in its molecule and preferably at least one alkyl substituent containing 1 to 12 carbon atoms located alpha to one of the amino groups. The molar ratio of the polyamine to the epoxy is such that, each amino group corresponds to 1.6 to 2.6 epoxy groups. The thermoplastic polymer content is preferably about 15% to 98% by weight with respect to the total weight of the polymer composition; the amount of epoxy resin modified by at least one aromatic polyamine is about 2% to 85% by weight with respect to the total weight of the polymer composition.