Effects of aminopropyl-terminated polydimethylsiloxane on structure and properties of waterborne polyurethane-acrylate

To achieve a good balance between mechanical properties and water resistance of the waterborne polyurethane (WPU) film, the hydroxylethyl acrylate (HEA) terminated waterborne polyurethane-acrylate (WPUA) emulsion was prepared by chain extension of 3,6-dioxa-1,8-octanedithiol (BOODT) and modification of aminopropyl-terminated polydimethylsiloxane (APT-PDMS). The effects of APT-PDMS on the microphase separation structure and the performance of WPUA film were investigated by varying the molar ratio of APT-PDMS to HEA. The introduction of APT-PDMS caused an increase in the content of hydrophobic groups, which could induce the rearrangement of the PDMS chain segments on the surface of WPUA during film formation. The rearrangement enhanced the surface hydrophobicity of WPUA, also improved the phase separation between hard and soft segments. The former was beneficial to obtaining better water resistance, while the latter was conducive to improving mechanical properties. However, the decrease in cross-linking degree will limit the mechanical properties and the water resistance with the increase in APT-PDMS/HEA molar ratio. The optimal balance between mechanical properties and water resistance can be achieved when the APT-PDMS/HEA molar ratio is 0.25. This work provides a feasible scheme for the industrial production of WPUA emulsions.