A new method to synthesize high solid content waterborne polyurethanes by strict control of bimodal particle size distribution |
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Affiliation: | 1. School of Mechanical and Precision Instrument Engineering, Xi''an University of Technology, Xi''an 710048, China;2. Faculty of Printing, Packaging Engineering and Digital Media Technology, Xi''an University of Technology, Xi''an 710048, China;3. Wuxue High School, Hubei 435400, China |
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Abstract: | A new method named two-step emulsification process was developed to synthesize high solid content waterborne polyurethanes by strict control of the bimodal particle size distribution. In the first step, a series of 40% solid content polyester-based (WPU-1) with low content of hydrophilic group and large particle size were firstly synthesized. In the second step, polyether-based prepolymers (WPU-2 prepolymers) with high content of hydrophilic group were firstly prepared and WPU-1 emulsions were used to emulsify WPU-2 prepolymers to obtain the final emulsions with high solid content (WPU-3). The particle size of WPU-3 present bimodal distribution and the diameter ratio and volume percentage of large particles to small particles in WPU-3 were able to be strictly controlled by this method. The viscosity of WPU-3 with 55% solid content was only 489.1 mPa s−1 when the diameter ratio of large particles to small particles was 9.2 and the volume percentage of large particles was 74%. |
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Keywords: | Waterborne polyurethanes High solid content Particle size distribution |
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