Synthesis and Characterization of Self-matting Waterborne Polyurethane Emulsion Modified by Silane Coupling Agent

Silane coupling agent has low surface energy, and its side chain contains organic groups that are easy to participate in the reaction. In the process of film formation, Si is easy to aggregate to the surface, which has the advantages of water and oil resistance, good permeability, low glass transition temperature and good thermal stability. Therefore, in this paper, four silane coupling agents such as KH540, KH550, KH560 and AEAPTMS were used to hydrophobically modify waterborne polyurethane (WPU). A series of self-matting waterborne polyurethane solutions were prepared with HTPB and PTMG as soft segments and IPDI as hard segment. The siloxane introduced in the WPU structure was hydrolyzed to form a Si-O-Si hydrophobic structure, which increased the crosslinking degree of the system and improved the water resistance of the system. It was also beneficial to increase the particle size and improved the extinction performance of WPU. Through comprehensive analysis, we found that the most suitable silane coupling agent for modifing self-matting WPU was AEAPTMS. After modification, the gloss of WPU leather coating can be reduced to 0.4 GU, and the surface energy can be reduced to 19.72 mJ/m2. It greatly improved the extinction performance and water and solvent resistance of WPU, and has a wide application prospect in the field of WPU leather finishing agent.