Studies On Structure And Properties Of Transparent Polyurethane Elastomer

The relationship of the structure and properties of transparent polyurethane elastomer (PU) based on isophorone diisocyanate (IPDI) was investigated in the study. All polyurethane elastomers prepared by a one-step bulk polymerization are clear and transparent. The relationship between the super-molecular structures and properties of polyurethane was studied by Differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA) and X-ray diffraction (WAXD).By theoretical calculation, the microphase separation degree was quantitatively evaluated by the copolymerization and physical crosslinking of PU. Results showed that higher crystallinity of soft segment domain , bigger macrocrystallite size of hard segment and more hydrogen bonds in hard segment domain enlarged the phase domains and improved microphase separation degree, which leaded to higher tensile strength, Young's modulus, energy to break point and thermal stability. The effect 6f microcrystallinite size on the light transparency of PU was not prominent because the microcrystallinity was nanocrystal. PU having appropriate degree of crosslinking exhibited good mechanical properties, thermal stability and light transparency.PU having higher molecular weight of soft segment exhibited excellent tensile properties and thermal stability. Effect of soft segment molecular weight of polyester PU on the mechanical properties and thermal stability was more sensitive than that of polyether PU. The light transparency of PU having high molecular weight of soft segment decreased with the increasing of soft segment mole content. PU having higher molecular weight of chain extender exhibited excellent tensile properties andthermal stability. With the increasing of hard segment content, mechanical properties of PU improved and light transparency of PU reduced little.