A copolymer having high strength and high elastic modulus is produced by copolymerizing (a) a polyamide oligomer prepared from a piperazine compound and an aromatic dicarboxylic acid and (b) a polyalkylene terephthalate monomer or a prepolymer thereof. The copolymer is useful as a rubber reinforcing...http://www.google.com/patents/US4433117?utm_source=gb-gplus-sharePatent US4433117 - Copolyesteramide and production of the same
