RHEOOPTICAL FOURIER-TRANSFORM INFRARED-SPECTROSCOPY OF POLYURETHANES AND THEIR BLENDS WITH POLYOLEFINS

Rheo-optical Fourier transform infrared spectroscopy was used to analy ze the orientational behavior of hard and soft segments of thermoplast ic poly(ether urethane)s (TPU-Et) and poly(ester urethane)s (TPU-Es) a nd their blends with a 20 mass-% contribution of either polyethylene ( PE) or polypropylene with an amorphous rubber phase CPP). The blends s how a reduced stress level, lower elongation-to-break and a lower degr ee of orientation of the segments - especially for the TPU-Es blends - compared to those of pure TPU's when uniaxially elongated. Blends of TPU-Et with PP show reduced stress but increased strain compared to pu re films of TPU-Et. This is caused by an improved adhesion of the rubb er phase in the polypropylene and the polyether phase of TPU-Et. Optic al micrographs visualize deformed polyolefin particles in elongated fi lms of TPU-Et/PP blends. In the TPU-Et/PP blend we could achieve equiv alent orientation for the polyolefin phase and the segments of TPU-Et caused by this higher phase adhesion compared to the other blends. Ori entation functions (OF's) of absorption bands which specifically repre sent hard or soft polyurethane segments or which are characteristic of the polyolefin phase have been calculated to monitor the molecular al ignment due to the mechanical treatment.