STRUCTURE, PROPERTIES AND MORPHOLOGY RELATIONSHIPS OF POLYURETHANE ELASTOMERS BASED ON URETHANE, AMIDE AND UREA DIOLS

The modifications of polyurethane elastomers were studied by introducing the urethane, amide and urea diols as chain extenders (4,4{dollar}spprime{dollar}-Diphenylmethylene diisocyanate/PTMG 1000/diol chain extender system). The secondary N-H active hydrogen donors in the urethane, amide and urea diols were utilized in the formation of hydrogen bonding in an attempt to improve the hard domain formation and the phase separation between the hard and soft domains. The MDI/PTMG 1000/1,4-Butandiol at various equivalent ratios were used as controls.; The tensile strength properties and hydrogen bond contents of the unsubstituted urethane and amide diol-based polyurethane elastomers were higher than that of 1,4-butanediol-based polymer. However, their thermal stability, Tm, were not as high as that of 1,4-butanediol-based polymer. Based on Bonart's model (extended-sequence hard segment), it was suggested that the presence of some strained-hydrogen bonding in the hard segments of the urethane and amide diols-based polymers would lower the crystallinity of hard domains. In order to release the strains, bending and twisting would take place in the polymer chains.; The strain-free hydrogen bonding network could be achieved by modifying the number of carbon in the backbone of the diols to be even number. The tensile strength of Amide(4)844 (even carbon number) were higher than that of Amide(1)844 (odd carbon number). The lower infrared absorption frequency of carbonyl group of Amide(4)844 and the trans configuration of N-H amide proton of Amide(4)808 indicated that the ordered and strain-free hydrogen bonding were obtained.; The methyl-substituents on the backbone of urethane and amide diols have an appreciable effect on diminishing the properties of the resulting polymers. They created disorder of the crystalline pattern, hindered the hydrogen bond alignment and disrupted the domain formation.; In summary, the major contributions to the properties of linear elastomers were the hard domain packing, the length of hard segment (size of hard domain), and the contents of hydrogen bonding as a minor contributor. The hydrogen bond content could only be considered as a co-variant parameter. This was due to the fact that hydrogen bonding network could be defected by the presence of methyl-substituents and internal strains.