SEGMENTAL ORIENTATION BEHAVIOR OF POLY(BUTYLENE TEREPHTHALATE-CO-TETRAMETHYLENE OXIDE) UPON UNIAXIAL DEFORMATION

The segmental orientation behavior of the thermoplastic elastomer [pol y(butylene terephthalate-co-tetramethyleneoxide)] has been studied wit h infrared dichroism and polarizing microscopy. The orientation of har d segments as well as soft segments has been determined as a function of draw ratio. The difference in the orientation behavior of soft and hard segments has been associated with the respective glass transition temperatures. It has been also established that annealing significant ly affects the deformation behavior. The segmental orientation has bee n observed to be strongly affected by the addition of small amount of the asymmetric chain extender. These results indicate that the crystal line structure of the hard segment can be significantly perturbed by t he heterogeneity of the chain extender. The birefringence observed usi ng the polarizing microscopy as a function of draw ratio correlates we ll with the orientation functions of hard segments rather than those o f soft segments. It is known that pi electrons in the hard-segment str ucture affect the refractive index significantly. Thus chemical struct ure of each segment in phase-separated thermoplastic elastomer should be considered in order to properly interpret birefringence data.