Emulsion stability and water tolerance of cationic waterborne polyurethane with different soft segment ratios between trifunctional polyether and bifunctional polyester

A series of cationic waterborne polyurethanes (WPU) was prepared using isophorone diisocyanate (IPDI) as the hard segment and polyester diol (PE2348), polyether triol (ZC330) or their mixture as the soft segment. The effects of the content of PE2348 and ZC330, crosslinking density on the particle size and its distribution, stability of WPU emulsion and the thermosstability, mechanical properties of WPU membrane were investigated. The results indicated that the increase of PE2348 in the mixed soft segment contributes to inhibiting the hydration, and the average particle size of the emulsion decreased because of the same cause. However, the stickiness of the corresponding film was increased and the elasticity deteriorated too. Structure uniform and suitable hydrophilicity of soft segment contributed to the stability, and higher crosslinking degree will contribute to the water-impregnation resistance of cationic waterborne polyurethanes membrane. Moderate hydrophilicity of polyurethane molecules and uniform distribution of hydrophilic structure are beneficial to uniform dispersion of polyurethane and better emulsion stability. If the miscibility between soft segments and hard segments and between the different soft segments is better, water resistance of the membrane will be improved significantly.