Study On Preparation And Properties Of Waterborne Polyurethane Modified By NH₂-POSS

As people pay more and more attention to environmental protection,the development of traditional solvent-based polyurethane is limited.Waterborne polyurethane（WPU）,which is environmental friendly and low VOCs,has become the new favorite in the polyurethane industry.Because waterborne polyurethane has the disadvantages of instability and poor heat resistance,various modification methods of WPU have become the focus of WPU research.NH₂-POSS has a cage structure and reaction group,and can significantly improve the performance of the product through chemical reaction.In this study,NH₂-POSS was used as modifier to improve the water resistance and heat resistance of waterborne polyurethane.The main research contents are as follows:（1）Using polypropylene glycol（PPG-2000,PPG-310）,2,2-dimethylpropionic acid（DMPA）,isophorone diisocyanate（IPDI）and 3-amino-polyhedral hemisiloxane（NH₂-POSS）as raw materials,a series of NH₂-POSS modified waterborne polyurethanes（WPUs）were prepared by one-pot method and high shear emulsification.The WPU/NH₂-POSS nanocomposites were characterized by Zeta potentiometer,viscometer,meter,dynamic light scatterer,Fourier transform infrared spectroscopy（FT-IR）,thermogravimetric analysis（TGA）,X-ray diffraction（XRD）,hydrogen nuclear magnetic resonance（¹HNMR）,atomic force microscopy（AFM）,transmission electron microscopy（TEM）,water contact Angle tester and gel penetration chromatography（GPC）.The results show that when the content of NH₂-POSS in WPU/NH₂-POSS nanocomposites was 2.95%～8.35%,the dispersion stability of the emulsion is improved,and the particle size of the emulsion decreases.In addition,with the increase of NH₂-POSS content from 0.00%（WPU0）to 13.19%（WPU5）,the thermal stability of WPU/NH₂-POSS nanocomposites also improved.When the addition of NH₂-POSS was 13.19%（WPU5）,the thermal stability of WPU/NH₂-POSS nanocomposites was the best.The water contact angle of WPU/NH₂-POSS nanocomposite membrane is larger than that of unmodified WPU membrane.When the amount of NH₂-POSS is 5.73%（WPU2）,the water contact angle increases from 80.2°to 84.5°;when the amount of NH₂-POSS is 8.35%,the water contact angle reaches the maximum and the water contact angle increases to94.6°,indicating that the hydrophobicity is improved.It can be seen from GPC that the polydispersion index of the WPU emulsion is decreased.In conclusion,when the addition amount of NH₂-POSS is 5.73%,WPU/NH₂-POSS nanocomposite material has the comprehensive properties of higher crosslinking density,better dispersion stability and lower emulsion viscosity,and its film has higher thermal stability and water resistance.（2）Using polypropylene glycol（PPG-2000）,2,2-dimethylpropionic acid（DMPA）,isophorone diisocyanate（IPDI）and 3-amino-polyhedron semisiloxane（NH₂-POSS）as raw materials,a series of NH₂-POSS modified waterborne polyurethane（WPU）were prepared by one-pot method and high shear emulsification waterborne polyurethanes（WPUs）were characterrized by the Zeta potentiometer,dynamic light scattering apparatus,Fourier transform infrared spectroscopy（FT-IR）and thermogravimetric analysis（TGA）,X-ray diffraction（XRD）,nuclear magnetic resonance hydrogen spectrum（¹HNMR）,atomic force microscope（AFM）and transmission electron microscope（TEM）,water contact angle tester,mechanical properties tester and gel permeation chromatography（GPC）.The results show that when the content of NH₂-POSS in WPU/NH₂-POSS nanocomposites is 2.61%～7.45%,the dispersion stability of the emulsion is improved,and the particle size of the emulsion decreases.In addition,the thermal stability of WPU/NH₂-POSS nanocomposites increases with the increase of NH₂-POSS content from 0.00%（WPU0）to 7.45%（WPU3）,and decreases with the increase of NH₂-POSS content from 7.45%（WPU3）to 11.83%（WPU5）.When the amount of NH₂-POSS was added,the water contact angle of WPU/NH₂-POSS composite was higher than that of pure WPU.When the amount of NH₂-POSS was added,the maximum water contact angle of WPU/NH₂-POSS composite was 106.3°,and the hydrophobicity was the best.When the addition of NH₂-POSS was 11.83%,the tensile strength of WPU reached the maximum value of 5.91 MPa,and when the addition of NH₂-POSS was 7.45%,the elongation at break of WPU reached the lowest value of 292%.It can be seen from GPC that the polydispersion index of WPU emulsion is more evenly dispersed after adding NH₂-POSS.In conclusion,when the addition amount of NH₂-POSS is5.09%,WPU/NH₂-POSS nanocomposite material has high cross-linking density,good dispersion stability and other comprehensive properties,and its film has high thermal stability and water resistance.Comparing the results of study（1）and study（2）,it can be concluded that the addition of NH₂-POSS can improve the water resistance,heat resistance and other properties of waterborne polyurethane.Comparing WPU with PPG-2000 and PPG-310 as soft segments and WPU with PPG-310 as soft segment,WPU with PPG-2000 as soft segment has better heat resistance and WPU with PPG-2000 and PPG-310 as soft segments has better hydrophobicity.