Study On The Click Chemistry Modification Of Waterborne Polyurethane

Waterborneborne polyurethane (WPU) coatings have received increased attention in recent coating technology development because of the environmentally friendly nature, good processability etc. However, some inferior properties of WPUs such as water resistance and hardness restirct its utility for high performance applications of WPU to some extent. It is important to modify the WPUs via various methods to improve inferior properties."Click"chemistry, as chemical combination tools, has won a lot of attention because of its high selectivity, quantitative yield, mild reaction conditions, and absence of by-products. The aim of this paper was to develop an an efficient way"click"chemistry for the modification of WPUs with nanosilica and silane coupling agent and to improve the properties of WPUs such as thermal stability, water resistance, weather resistance and hardness of WPUs.The main contents of this paper were described as follows:1. Synthesis of alkyne-containing waterborne polyurethane. Waterborne polyurethane bearing alkyne functions as pendant groups was synthesized by the reaction between DPPD , IPDI and other raw materials. The alkyne-functionalized WPU was characterized by IR and TGA. Carbon layer upper part of the material was formed juring the burning of the material and the overall final char yield increased with the increase of DPPD.2. Click modification of WPU with silane coupling agent. The copper CuSO₄/Na_asc catalyzed Huisgen 1, 3-dipolar cycloaddition was applied to the modification of alkyne-based WPUs with azide functionalized silane coupling agent (3-azido- propyltriethoxysilane). The modified WPUs were characterized by IR, TGA, contact angle measurements and hardness. The properties of click modified WPUs such as thermal stability, water resistance and hardness of WPUs were improved. When the content of silane coupling agent was 5%, final char yield, water contact angle and hardness respectively reached 4.7%, 75°, 3H.3. Click modification of WPU with nanosilica. The copper catalyzed Huisgen 1, 3-dipolar cycloaddition was undertaken between alkyne-functionalized WPUs and azide-functionalized silica nanoparticles. The modified WPUs were characterized by IR, SEM, TGA, contact angle measurements, water absorption, UV-vis spectra and hardness. The properties of click modified WPUs such as thermal stability, water resistance, weather resistance and hardness of WPUs were improved. When the content of silane coupling agent was 3%, water contact angle and hardness respectively reached 91°, 2H.