Effects of soft segment and microstructure of polysiloxane modified cationic waterborne polyurethane on the properties of its emulsion and membrane

Cationic waterborne polyurethane (WPU) is limited in wider applications due to its poor water resistance and worse flexibility. However, polysiloxane is widely used because of the advantages in these two aspects. To improve the water resistance and the flexibility of cationic WPU, combining with the characteristics of organosilicon compound, the hydroxyalkyl-containing bifunctional group polysiloxane (PPC) and self-made trifunctional group modifier PPS were used to modify the cationic WPU. The particle size and size distribution of the modified cationic WPU emulsion, the water resistance and the surface moisture resistance of the corresponding membrane were investigated. The results indicated that the cationic WPU modified by PPC will show the moderate hydrophilicity, which had positive effect on the water resistance. Although PPS had a negative effect on the dispersion and the emulsification of the polymer, a small amount of introduction can greatly improve the water resistance and the water repellency of its membrane. (paper)