Study On Systhesis And Performance Of Polyurethane Elastomer Uesd For Melt-spinnable Fiber

Polyurethane elastomers (PUEs) are linear segmented copolymers consisting of a relatively flexible component derived from a macrodiol, called the soft segment, and a relatively hard and stiff component derived from a diisocyanate and a chain extender, called the hard segment. Thermodynamic incompatibility of the so-called soft and hard segments leads tomicrophase separation. Therefore, a correct design of the molecular structure becomes crucial as it provides the mechanical properties that meet our needs in every aspect.In our work, PUEs have been modified in view of hard and soft segment respectively. The mechanical properties, morphology, thermal stability and shape memory effect properties were examined by means of FTIR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WXRD), dynamic mechanic thermal analysis (DMTA), stress-strain measurement and Hydrolysis stability testing. Besides, various methods of controlling the molecular structure and morphology of hard-segment and soft-segment domains have been already introduced to obtain higher performance PUEs.Polyurethane elastomers with various wt % of hard segment were synthesized by bulk Polymerization. The results indicated that the PUs would show different preformance by changing the mol ratio of MDI and BDO (hard segment). Finally, Better mechanical properties and 80～85% of shape recovery were obtained at 31～35 wt % of hard segment content. Overall, the control of hard segment content and composition in PU block copolymers is very important in determining their physical properties.A series of Polyether-Polyester polyurethane elastomer has been synthesized by two-step solution process. Their morphologies, shape-memory properties, thermal stability and mechanical properties were analyzed with the measurements of FTIR, WXRD, AFM, TGA, DMA, tensile tests and Hydrolysis stability testing. The results showed that the introduction of polyether (PTMG) into the soft segment resulted in reduced interactions among the hard segments, and this made the copolymers easily elongated but low tensile strength. Such copolymers presented relatively high Shape-recovery ratio. Besides, good hydrolysis - resistant capability has been obtained with adding more polyether into soft segment. Finally, Better mechanical properties, water resistance and 80～85% of shape recovery was obtained at 4～5% PTMG content. Overall, the composition of soft segment in PU block copolymers is very essential to determine their properties. Besides, PCL has been used as soft segment to compare with PBA-based one. Its heat resistance and mechanical properties show excellent than the PBA-based polyurethane as the data tell.Polyurethanes based on hydroquinone bis- (b-hydroxyethy) ether (HQEE) and 1, 4-butanediol (BDO) as a chain extender were prepared by two-step solution polymerization process. Their hydrogen bonding and morphological structure were studied by means of FTIR, DSC, TGA, AFM, DMA, tensile tests and water-aging test. In conclusion, with the proportion of HQEE/BDO increased, the degree of microphase separation was getting higher, and the heat resistance and mechanical properties were improved because of the increased benzene groups. HQEE/BDO-based TPU had better heat resistance and mechanical properties compared with the conventional one.