Preparation And Properties Of Waterborne Polyurethane Modified And Its Nanocomposites

Waterborne polyurethane (WPU) is one kind of polymer materials, which uses water as a dispersion medium. WPU has many advantages, such as non-toxic, no peculiar smell, and pollution-free etc., and it has been widely applied in leather decorates, automotive refinishes, adhesive, printing ink, protective coating, and other areas. However, in order to realize self-emulsifying in the preparation process, it usually needs to introduce hydrophilic groups or chain segments into the WPU molecular chain. The introduction of hydrophilic groups or chain segments will decrease the water resistance, solvent resistance, and mechanical strength etc. of WPU film, and this will greatly affect the application of WPU in real life. So, it is necessary to modify the WPU to improve its combination property. In this thesis, it mainly uses organosilicone and carbon nanotube to modify the WPU.In the first part, a hydroxyl-component WPU with a cross-link structure of Si-O-Si groups was prepared by means of 3-aminopropyltriethoxysilane (APTES) modification. Then, with the addition of hydrophilically modified polyisocyanates, a series of novel 2K-WPUs bearing internal and external cross-linking structure was received. The results indicate that APTES has been successfully introduced into WPU molecular chains, and the 2K-WPUs form a cross-linked structure of Si-O-Si. The thermal stability, solvent resistance, and water resistance of 2K-WPU are improved with the aid of APTES.2K-WPU films containing 4 wt.% APTES possess the strongest resistance to ethanol, as well as resistance to acetone and dichloromethane to a certain extent. With addition of APTES,2K-WPU films also exhibit excellent tensile strength and breaking elongation.In the second part, the uniform multiwalled carbon nanotube (MWCNT) dispersion was prepared with the sodium dodecyl sulfate (SDS) or sodium dodecylbenzenesulfonate (SDBS) surface modification. Then, a series of MWCNT/WPU nanocomposites was obtained by the way of functionalized MWCNT dispersion and WPU direct mixing. The research shows that the optimal dispersion effects of MWCNTs in WPU matrix turn up in 8 wt% SDS/MWCNT/WPU and 4 wt% SDBS/MWCNT/WPU. The thermal property, surface hydrophobicity, water resistance, and mechanical properties are improved with the addition of MWCNTs. The static contact angle maximum increase 18°, and the swelling ratio can low to 10 %. The tensile strength, breaking elongation, and elasticity modulus can as high as 246 MPa,256%, and 33.5MPa, respectively. In comparison to SDBS/MWCNT system, SDS/MWCNT system has the better improvement effect on the combination properties of WPU. However, the addition of MWCNT leads to the transparency of WPU reducing.