| Waterborne polyurethane (WPU) is a kind of polyurethane emulsion systems which treats water as the dispersion medium. Compared to traditional polyurethane which treats organic solvents as dispersion medium, WPU has an advantage with green pollution-free and safe reliable, therefore WPU has a broad development prospect. However, the water resistance of WPU film has decreased due to reats water as the dispersion medium, which limiting the WPU materials in various fields. Therefore, it's an important thing to study the relationship between structure and properties of aqueous polyurethane, then can use practical new technology and new methods to improve the water resistance of the aqueous polyurethane, which can expand applications of aqueous polyurethane and improve environment of production and applications of polyurethane materials.Firstly, This paper has prepared IPDI waterborne polyurethane with self-emulsifying, explored the impact of emulsification of WPU emulsion and the water resistance and mechanical properties of the produced film with different polyurethane prepolymer synthesis process, further confirms the relationship between the performance and structure of aqueous polyurethane. By studying the different synthetic procedures of prepolymer, It found that we can get polyurethane emulsion which can easily emulsified and its film has excellent water resistance and mechanical properties by one-step synthesis. Then synthesized prepolymer by one-step, we studied the content of soft segment, the amount of the hydrophilic chain extender(DMBA) and the after chain extender(DETA), how affect the emulsion and film performance. The study found that when Rl is 2.5-3.5, the amount of DMBA is 2.4%-4.7%, the amount of DETA is 100%, it can be obtained IPDI water-based polyurethane which has integrated high performance.Secondly, by the addition of polymeric emulsifier in the preparation of an aqueous polyurethane, making use of internal and external synergies can be prepared polyurethane which has strong water resistance, exploring the different proportion of emulsifier and emulsification time to film the effect of water resistance, the research found that when R1 is 2.5, the amount of DETA is 100%, the amount of external emulsifier is 0.5%, the reaction time is 10min, the amount of DMBA is 3.6%, the water resistance of film can be the best, water absorption is 4.1%, which is superior to conventional materials within the WPU was prepared under the same conditions emulsification of water absorption (19.2%). And the basic properties of the polyurethane material under optimal water resistance ratio were characterized and found that this time the film's mechanical properties and thermal properties do not fall within the more traditional type emulsion film performance.Finally, it explored the mechanism of internal and external collaboration emulsification to improve water resistance of WPU. There may be two reasons, one is outside the emulsifier is added to improve the emulsifying properties of the polyurethane emulsion, colloidal particle size decreases, the close integration of film formation particles after the film formation fewer voids, the water molecules hardly penetrate inside the film, so that the water film is improved; the second is outside the emulsifier film drying process, will move to the lower surface of the film surface can be driven on surface hydrophilic group be embedded, the contact angle of water droplets and film surface is increased, reducing the surface tension. |
PDF Full Text Request