pH值对正硅酸乙酯原位改性水性聚氨酯复合乳液性能的影响

The Effect of pH Value on the Properties of In-situ Modified Waterborne Polyurethane Composite Emulsion by Ethyl Orthosilicate

为了研究正硅酸乙酯(TEOS)原位改性水性聚氨酯(WPU)时,TEOS溶胶-凝胶阶段的pH值对复合水性聚氨酯力学及防腐等性能的影响,通过调节分散介质的pH制备了一系列复合WPU。并用粒径分析仪、傅里叶红外光谱仪、扫描电子显微镜、吸水率测试、热重分析仪、万能力学试验机和电化学工作站表征了这些复合WPU胶膜和涂层的性能。结果表明,加入TEOS会极大减小粒径;酸碱会使氢键键合的N—H变为游离,胶膜硬段的最大热分解速率温度降低;在酸催化的胶膜中形成的SiO_(2)粒子呈椭球状,较碱性下形状更加复杂,分布更加均匀,且可有效降低胶膜吸水率(比pH值=7时降低10.34%),提升拉伸性能(拉伸强度比pH值=7时提高13.41 MPa,断裂伸长率提高124%),但pH值>9时制备的复合WPU更适合作为金属防腐涂层。

In order to study the effect of tetraethyl orthosilicate(TEOS)sol-gel phase pH value on the mechanical and anti-corrosion properties of the composite waterborne polyurethane when in-situ modified waterborne polyurethane(WPU)by TEOS,a series of WPU composites were prepared by adjusting the pH value of the dispersion medium.Particle size analyzer,Fourier infrared spectrometer,scanning electron microscope,water absorption testing,thermogravimetric analyzer,universal testing machine and electrochemical workstation were used to characterize the performance of these composite WPU films and coatings.The results show that the addition of TEOS could greatly reduce the particle size.Acid and alkali make hydrogen-bonded N-H free,and the maximum thermal decomposition rate temperature of the hard segment of the film decreases.The SiO_(2) particles formed in the acid-catalyzed film are ellipsoidal,which are more complex in shape and more evenly distributed than in alkaline,which could effectively reduce the water absorption of the film(reduced 10.34%than PH=7)and improve mechanical properties(comparing with pH=7,the tensile strength increases 13.41 MPa,the elongation at break increases 124%),but the composite WPU prepared by catalysis at pH>9 is more suitable as a metal anticorrosive coating.