Synthesis and properties of crosslinked self-healing waterborne polyurethane
Dynamic exchange reaction exchanged by disulfide bonds can endow waterborne polyurethane with self-healing ability.However,the weak dynamic covalent bonding strength makes it difficult to achieve both self-healing and mechanical proper-ties of polyurethane elastomers.Polyepoxypropane ether triol and 2-hydroxyethyl disulfide containing disulfide bonds were used to introduce both disulfide bonds and branched structures into polyurethane molecules,resulting in high-strength,cross-linked self-healing waterborne polyurethane.Waterborne polyurethane emulsion was synthesized from iso-phorone diisocyanate(IPDI),polytet-rahydrofuran ether glycol,polypropylene oxide ether triol,2-bis(hydroxymethyl)propionic acid(DMPA)and 2-hydrox-yethyl disul-fide(HEDS).A series of cross-linked self-healing waterborne polyurethane membranes were obtained by adjusting the mole ratio of DMPA and HEDS.Fourier transform infrared spectroscopy and Raman characterization spectra results confirm the successful intro-duction of disulfide bonds into waterborne polyurethane.The waterborne polyurethane emulsion shows excellent storage stability.The cross-linked self-healing waterborne polyurethane membrane shows much higher tensile strength and self-healing ability than that without disulfide bonds.When the molar ratio of DMPA and HEDS is 1∶1,the tensile strength is improved from 13.1 MPa without disulfide bond to 24.2 MPa.The cross-linked self-healing waterborne polyurethane membrane shows high self-healing tensile strength of 19.4 MPa and self-healing rate of 80.1%.
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