Design-properties relationships of polyurethanes elastomers depending on different chain extenders structures

In this study, the effect of the structure and amount of the chain extenders on the morphological image and physico-chemical properties of some new polyurethane elastomers has been investigated. To achieve this, three series of polyurethane elastomers based on poly(tetramethylene ether) glycol, hexamethylene diisocyanate and chain extenders with different structures (triethylene glycol, 3,6-dithia-1,8-octanediol, 1,6-hexanediol) were synthesized. The chain-extenders which introduce oxygen or sulfur atoms into the polyurethane backbone chains (hard domains) change the behavior of the properties compared to the corresponding polyurethanes chain-extended with aliphatic diols. The structures of the new polyurethane elastomers were examined by FTIR, X-ray diffraction analysis and by atomic force microscopy (AFM). They were also characterized for thermal and tensile properties. The polyurethanes with sulfur into their hard segment structure were found to exhibit improved thermal stability properties and equivalent mechanical properties with polyurethanes obtained with aliphatic diols. This is due to the extensive and many fold hydrogen bond network that characterizes polyurethanes with sulfur in their hard segment structure.