Microphase separation idea to toughen CO2-based waterborne polyurethane

CO 2 based waterborne polyurethane (CO 2 -WPU), especially high CO 2 content one, suffered from the poor flexibility at low temperature due to high content of rigid carbonate segment. Here a microphase separation idea was proposed by introducing poly(butyl acrylate) (PBA) as soft phase to toughen CO 2 -WPU via an organic solvent free route, i.e., the polymerizable butyl acrylate acted as a pseudo-solvent during CO 2 -WPU prepolymer synthesis, it then experienced radical polymerization after formation of CO 2 -WPU, and finally forming a material with multi-phase structure. Benefiting from the separation of soft PBA phase and hard CO 2 -WPU phase in micro-size, a 368% increase in elongation at break (ε b ) and nearly 65 times increase in toughness at -10 °C was observed when PBA loading increased from blank to 65 wt%. As a comparison, the tensile strength (σ m ) and ε b of the PBA/CO 2 -WPU blending film at room temperature was only 4.4 MPa and 383% when PBA loading was 50 wt%, while the PBA/CO 2 -WPU multi-phase film showed σ m of 18.8 MPa and ε b of 489%, respectively. The toughening effect was attributed to the more uniform micro-phase separation structure caused by molecular level inter-migration between PBA and CO 2 -WPU during preparation process.