Toluene diisocyanate based polyurethanes with amide extenders were synthesized poly(propylene oxide) with a number average molecular weight of 2000 and endcapped with toluene diisocyanate was used as the polyether segment. The chain extenders were based on poly(hexamethylene terephthalamide): hexamethylene diamine, bisamine-diamide and bisamine-tetra-amide. The linear poly(ether bisurethane-bisurea-amide)s (PUA) were colorless transparent thermoplastic elastomers with a high molecular weight. The polymers were analyzed by IR and DSC, the morphology studied by TEM, the mechanical properties studied by DMTA and the tensile, the elastic properties by compression and tensile set and thermal stability by melt rheology. The phase separation with these amide extenders was by crystallization. Increasing the length of the amide chain extender increased the modulus and the melting temperature of the PUA without changing the good low temperature properties. Also the elastic properties improved with amide segment length. The fracture stress increases with amide extender length. At 200 °C, the melt stability of the PUA with the bisamine-diamide chain extender was good.
Schuur, van der, M., Noordover, B. A. J., & Gaymans, R. J. (2006). Polyuretehane elastomers with amide chain extenders of uniform length. Polymer, 47(4), 1091-1100. https://doi.org/10.1016/j.polymer.2005.11.074