Synthesis of high-toughness waterborne polyurethane utilizing self-emulsifying CO2-based polyols

In this work, a self-emulsifying CO2-based polyol (LAPEC) was prepared by the terpolymerization of propylene oxide, allyl glycidyl ether and CO2, followed by thiol-ene click reaction with mercaptopropionic acid. And the carboxyl group was successfully introduced into LAPEC verified in 1H NMR. LAPEC was served as both soft segments and internal emulsifiers for WPU. Meanwhile, γ-aminopropylmethyldiethoxysilane (KH902) was also employed to improve the mechanical properties of WPU. Compared to dimethylol propionic acid (DMPA), WPU emulsion prepared by LAPEC had smaller particle size and higher emulsification efficiency. And the performance differences between LAPEC-based WPU films (LWPUs) and DMPA-based WPU films (DWPUs) with different hard segment contents were studied. The stronger hydrogen-bonding interactions improved the tensile strength, toughness and thermal stability. Compared with DWPU, the tensile strength and the elongation at break of LWPU respectively increased from 17.8 to 21.1 MPa and from 302.3 % to 356.5 %, when their hard segment content was both maintained around 37 wt%. Meanwhile, due to rougher surfaces and more hydrophobic silicon clusters, LWPU had stronger surface hydrophobicity. Therefore, LAPEC can provide a new way to synthesize WPU with high toughness and can be potentially used for flexible substrate coatings in the future.