Synthesis and characterization of an ultra-soft poly(carbonate urethane).

A high performance, thermoplastic polyurethane elastomer was synthesized with methylene bis(4-cyclohexylisocyanate), 1,4-butanediol as a chain extender and a polycarbonate polyol containing 1,6-hexanediol and 3-methyl-1,5-pentanediol. SAXS data evidences an interdomain “center-to-center” distance of 45 Å. DSC traces evidence one glass transition temperature and weak melting region. Surprisingly, the material is ultra-soft with a Shore A hardness of 64, but does not undergo any blocking. DMA analysis reveals a low temperature secondary relaxation and the glass to rubber transition followed by a rubbery plateau. In tensile set experiments strain recovery averaged 96–98%. The PCPU exhibits partial self-healing after rupture without the addition of additives or imbedded healing agents. Self-healing is attributed to interdiffusion and hydrogen bonding mechanism, where rehealing is possible. FTIR measurements characterize hydrogen bonding. [ABSTRACT FROM AUTHOR]