Robust self-healing waterborne polyurethane coatings via dynamic covalent Diels-Alder bonds for corrosion protection |
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Authors: | Changjiang Yu Zhanhua Wang Guoxia Fei Xi Zhang Martina Salzano de Luna Marino Lavorgna Hesheng Xia |
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Institution: | 1. State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, China;2. Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Naples, Italy;3. Institute for Polymers, Composites and Biomaterials, National Research Council of Italy, Portici, Italy |
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Abstract: | For waterborne polyurethanes (PUs), balancing robust mechanical performances and excellent self-healing ability is a great challenge. Here, we show that this goal can be achieved by a rational tuning of the PU chemistry. In particular, we synthesized an anionic self-healing waterborne PU using acetone process, in which 2,2-bis(hydroxymethyl)propionic acid (DMPA) serves as inner emulsifier, thermally dynamic Diels-Alder bonds act as healing motifs and hexamethylene diisocyanate trimer is the crosslinker. The mechanical performance can be tuned by increasing DMPA concentration due to the gradually increased hard segment contents and ionic interactions. The tensile stress and elongation at break of films containing 5.6 wt% of DMPA are 24.9 MPa and 911.9%, respectively. Moreover, dynamic reversible Diels-Alder bonds located in main chains and cross-linking points ensure excellent self-repairing capability. Upon mechanical damage, the tensile stress can be restored to 95% of its initial value. Electrochemical impedance spectroscopy also points out an outstanding barrier ability and excellent corrosion protection performance of the coatings, which can be recovered even after serious damages. |
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Keywords: | corrosion protection Diels-Alder bonds ionic interaction mechanical performance self-healing waterborne polyurethane |
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