Investigation of the migration ability of silicone and properties of waterborne polyurethanes

A series of silicone–waterborne polyurethanes (WPU) are prepared by a pre–polymer method based on poly(tetramethylene ether glycol), isophorone diisocyanate, and polydimethylsiloxane (PDMS). The effect of the molecular weight of PDMS and film–forming temperature on the properties of WPU are investigated. The hydrophobicity of the films is characterized by X–ray photoelectron spectroscopy, contact angle and water absorbed measurements. With increasing molecular weight of PDMS in the WPU films, the contact angles increase, surface free energies decrease, and a substantial enrichment of silicon moieties at the film–air interface is observed. As the film–forming temperature increases, more silicone migrates to the film–air interface, which improves the hydrophobicity of the film bulk. The extent of variable phase separation caused by the mobility and incompatibility between silicone and the WPU segment is observed in the matrix of the WPU films by scanning electron microscopy. The degree of phase separation increases with the molecular weight of PDMS and film–forming temperature.