The stress-induced crystalline phase transition in poly (tetramethylene terephthalate)

Abstract

For explanation of the stress-strain behaviour of highly oriented and annealed poly(tetramethylene-terephthalate) which is mainly influenced by a stress-induced crystalline phase transition a platzwechsel model is proposed: the monomer units in the crystalline parts of the material have two distinct conformations with low energy. The energy difference of the two conformations depends on the applied stress which means that depending on stress two crystalline phases exist. The transition between them is described by the time-independent solution of the platzwechsel model in terms of an equation of states. Additionally the periodic solution of the model gives a good qualitative description of the dependence of the complex compliance on static strain, which had been measured in dynamic mechanical experiments by Davies et al. [10].