| Waterborne polyurethane (WPU) is dispersible in water medium, which is non-toxic, non-flammable and environmental friendly and has advantage in price and cost compared with solvent borne polyurethane. So people are more inclined to study the development and application of waterborne polyurethane. But WPU is still have many defects in performance and leather simulation. The domestic synthetic leather products are still concentrated in the production of solvent borne polyurethane. Most application of waterborne polyurethane is concentrated in leather finishing and leather adhesive. As the study of waterborne polyurethane synthetic leather has just started in china, if people want WPU become more practical and substitute PU, the based work is to improve the preparation and properties of waterborne polyurethane.To address these issues, we synthesized a environmental-friendly waterborne polyurethane and analyzed the forming properties. First we choose H12MDI and PTMG as the main material, BDO as small molecular extender and DMBA as hydrophilic chain extender to synthetic WPU emulsion.H12MDI is a kind of isocyanate which is not contain benzene ring and yellowing resistance. Compared with MDI film, H12MDI’s air permeability increased by15%, water vapor permeability increased by17-25%, breaking strength increased by31.26%and elongation increased by20.4%. DMBA WPU film had better water vapor permeability and mechanical properties than DMPA WPU film and its moisture absorption increased by25%-38%. DMBA had lower dissolve temperature and organic solvent solubility than BMBA, that greatly reducing and avoiding the use of organic solvents.Secondly, under the optimize conditions, we prepared waterborne polyurethane film and waterborne polyurethane coated fabric. Experimental conditions of film and coated fabric including:hard segment content, DMBA content, thickness, drying temperature and so on. Trough the comparative analysis between film and coated fabric, when hard segment content is25.27%and DMBA content is7%, film and coated fabric had the relatively good performance. Finally, we made some relevant performance measurement and analysis of the obtained WPU emulsion, films and coated fabrics:(1) The results of WPU emulsion test on appearance and stability:H12MDI emulsion had good stability. When pre-polymerization and extended chain reaction temperature were about80℃, the appearance and stability of the WPU emulsion was best.(2) The test results of WPU film characterization and surface morphology:With the increase in hard segment content, Absorption peaks of CO and NH in FTIR curve moved forward and peak value decreased, crystalline melting temperature decreased from66.9℃to56.08℃, surface holes were small, deep, regularly with sharp edge, and the surface particles increased.(3)The analysis result of air permeability, moisture vapor permeability, moisture absorption and mechanical properties on for WPU film and coated fabric:As the hard segment content increased from25.27%to51.25%, the film’s air permeability increased36.63%, water vapor permeability decreased by46.8%and the contact angle increases, coated fabric’s breaking strength increased7.34%and elongation reduced by47.7%. when DMPA content increased from5%to8%, the film’s air permeability decreased by64.62%, water vapor permeability increased nearly2times, water absorption increase of190.2%,contact angle became smaller, coated fabric’s breaking strength increased29.3%,and elongation decreased by60.2%. Air permeability, water vapor permeability and water absorption of WPU was also impacted by film thickness and drying temperature.(4)The result of the performance comparison between WPU film and coated fabric:The hole of coated fabric was0.5-1.5um, and the hole of film is1-2um. Air permeability of coated fabric was better than the film. When DMBA content is low, film’s moisture absorption is better than coated fabric’s. But when DMBA content was high enough, film swelling, moisture absorption became higher than coated fabric. Breaking strength of the coated fabric was99.4%higher, while elongation was90.59%than the film.The result shows that, H12MDI waterborne polyurethane had good emulsion stability. Water vapor permeability and mechanical property of the coating is better, which could reduce the pollution released during the preparation of the WPU. Due to the lower cost and safety process, the material is also a kind of WPU synthetic leather which is kindly to the environment. |
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