Thermodynamics of the deformation of a block polyether-polyester copolymer☆

Abstract The thermodynamics of the deformation of a block copolymer based on polybutylene terephthalate and the copolymer of tetrahydrofuran with propylene oxide has been studied by deformation calorimetry and wide and small angle X-ray diffraction. For low degrees of stretching the deformation behaviour of such a block copolymer is similar to that of solid polymers. The transition of the sample to the oriented state is accompanied by rise in internal energy and the reversible deformation of the oriented samples is determined by the deformation of the a morphous phase.