Effects Of Hydrogen Bond And Steric Hindrance On The Viscoelasticity Of Polyurethane

Polyurethane is an important viscoelastic material.Hydrogen bonds between molecules have an important influence on viscoelastic property of polyurethane.By choosing different chain extender,isocyanate and polyether polyol,we studied the influence of hydrogen and steric on polyurethane viscoelastic.First,we use two types of chain extender:One is in maintaining the chain extender backbone same length,changing the length of the side chain of the chain extender,studying the effect of pendant steric on polyurethane viscoelasticity.;Another is to change the length of the backbone chain extender,studying the effect of the length of chain extender on polyurethane viscoelasticity.The results show that with the increase of steric hindrance of the side chain of the polyurethane,hydrogen bond is weaken and maximum loss factor is improved from 0.39 to 0.56;with the decrease of length of the chain extender,hydrogen bond is weaken and maximum loss factor is improved from 0.39 to 0.32;Odd-even affect polyurethane viscoelasticity.Second,we use different steric hindrance isocyanates,including presence or absence phenyl isocyanate,isomer content and flexible group number,studying the effect of steric hindrance of isocyanate.The results show that with the increase of isocyanate steric hindrance,hydrogen bond is weaken and maximum loss factor is improved,such as PPDI and TDI-100 polyurethane,tanδ from 0.23 to 0.71.Finally,we study the effect of polyether polyols species,polyether polyols molecular weight,polyether polyols with different molecular weights and polyether content on polyurethane viscoelastic.The results show that with the increase of pendant steric,hydrogen bond is weaken and maximum loss factor is improved from 0.46 to 0.76;with the increase of molecular weight,hydrogen bond is weaken and maximum loss factor is improved from 0.30 to 0.53;with the increase of PTMG-2000,hydrogen bond is weaken and maximum loss factor is improved from 0.30 to 0.55;with the increase of soft content,hydrogen bond is weaken and maximum loss factor is improved from 0.47 to 1.02.