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The aqueous polyurethane is a polyurethane particles dispersed in water to a binary colloidal system, the molecular chain containing hydrophilic groups, and thus has a strong affinity with water. Not only does it have excellent performance, solvent-based polyurethane low temperature resistance, good flexibility, bonding strength and also has a non-toxic, non-flammable, odor, do not pollute the environment, safety, processing, and good film formation permeability. In recent years, organic solvent prices and environmental protection departments to strictly limit the use of organic solvents and waste emissions, solvent-based polyurethane waterborne polyurethane instead become an important development direction. Over the past decade, the study of domestic water-based polyurethane multi-aromatic isocyanate as raw materials, poor weather, easy-yellowing, can not meet the special requirements of the market. As people's living standards improve, more and more urgent demand for environmental, health, and high-performance products, green chemicals gradually become the mainstream of the future development, thus aliphatic isocyanates production of more environmentally friendly water-based polyurethane products, will be the response to this one of the main development direction of the trend. This topic selected aliphatic hexamethylene diisocyanate (hexamethylenediisocyanate, HDI), polybutylene adipate diol (poly butyleneglycol adipate, referred to as PBA), dimethylol propionic acid (dimethylolpropionic acid, referred DMPA as the main raw material) and small molecule diols using anion self-emulsifying method, synthesized a series of a stable polyester water-based polyurethane emulsion, then crosslinked film with commercially available cross-linking agent, and cotton fabric coating. Study the content of the hydrophilic group, NCO / OH molar ratio, the molecular weight of the soft segment as well as the type of chain extender on the properties of the aqueous polyurethane emulsion of the mechanical properties of the film, the thermodynamic properties of the film and a coating fabric whiteness, waterproof moisture permeability , found: With the increase in the amount of DMPA, the emulsion particle size is reduced, the increase in viscosity of the emulsion, and the improvement of the mechanical stability of the emulsion; increased water absorption of the coating film, water resistance decreased, the film tensile strength change. trend to increase, but not obvious; lower glass transition temperature, melting at elevated, and the increasing degree of micro-phase separation; heat stability did not change significantly. With the initial NCO / OH molar ratio increases, the emulsion particle size increases, the emulsion viscosity decreases, emulsion stability decreased; coating water absorption decreased, but to reduce the effect was not significant; film pulled up strength first increased and then decreased ; glass transition temperature increases, the degree of micro-phase separation is reduced; heat stability significantly reduced. With the increased molecular weight of polyol PBA emulsion Appearance translucent to milky, viscosity decreases gradually decreased stability; film tensile strength, elongation at break are increased; lower glass transition temperature, melting at elevated The increased degree of micro-phase separation; improve thermal stability. Have an impact on the performance of different chain extender on waterborne polyurethane emulsion, compare remarkable performance of the mechanical properties of the film, the better resilience polyurethane EDA chain extender, high strength polyurethane BPA chain extender of BDO between two between. Cotton fabric coating finishing, curing temperature and time process factors PU polymer and the degree of crosslinking of cotton fiber and film formed on the surface has an important impact. Low temperature, short time, low water pressure resistance value; high temperature for a long time, whiteness decreased significantly better overall performance in the 1 ~ 2min crosslinked at 140 ℃. The coating amount increases, the whiteness of the coated fabric is slightly lower; larger moisture permeability decrease; water pressure is increased; increase in the molecular mass of the polyurethane soft segment is conducive to the improvement of resistance to hydrostatic, but will cause the moisture permeability decline.
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