Preparation of an ionic/nonionic polyurethane-silicone dispersion (PUSD) with a high solid content and low viscosity using complex soft segments
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A series of ionic/nonionic polyurethane-silicone dispersions (PUSDs) with a high solid content and low viscosity were prepared using isophorone diisocyanate as the hard segment, polytetrahydrofuran polyether diol (PTMG) and polysiloxane diol (PESI) as the complex soft segments and an ionic/nonionic low molecular weight polyether diol (DPSA) as the hydrophilic, chain-extending agent. The morphologies and rheological properties of the ionic/nonionic PUSD were examined using particle-size, TEM, and viscosity analyses. The hydrophobic and mechanical properties of the dispersions were also tested. It was found that under the conditions of a constant NCO/OH ratio (2/1) and weight percentage of DPDA (6%), the PUSD dispersions with higher PESI contents possessed higher average particle diameters and wider particle-size distributions. Particles in the PUSD dispersions are generally spherical and have a typical core–shell structure due to the use of complex soft segments. However, the solid content of the ionic/nonionic PUSD increased first and then decreased as the weight ratio of PESI to PTMG increased. When the ratio ranged from 4/10 to 6/10, the max solid content of the ionic/nonionic PUSD reached up to 58%, but the viscosity of the PUSD was less than 400 mPa.s−1. Meanwhile, the water contact angle of the films increased due to the formation of a crosslinking structure on the side of the PUSD macromolecule, and when the weight ratio of PESI to PTMG varied from 3/10 to 7/10, the water contact angle of the films increased from 48.3° to 72.3°. In addition, both the freeze-thaw and thermal stabilities of the PUSD dispersions were enhanced as the weight ratio of PESI to PTMG increased. The PUSD coating had good mechanical properties as well.
KeywordsHigh solid content Polyurethane-silicone dispersions Complex soft segments Hydrophobic properties Weather resistance
This work was partially supported by the Chemical Additives and Surfactants Key Laboratory of Sichuan Universities (Projects 2015JXY02, 2014JXY04), the Sichuan University Talents Project (Projects 2014RC14, 2015RC55), and the Sichuan Province Department of Education (Project 16ZB0254). The authors also thank all project team members for performance testing of the products in this study.
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