High-Strength Self-Healing Polyurethane Composites Reinforced by Hydrogen Bonds

Striving to enhance the equilibrium between the mechanical attributes and self-healing capabilities of self-healing materials has remained a formidable challenge. Hydrogen bond-type self-healing materials have drawn an increasing amount of attention. Herein, we incorporated uracil units (UPy), which possess multiplicity functional groups conducive to the formation of hydrogen bond density, into the polyurethane (PU) matrix as a part of the chain extender. High hydrogen bond density inside the PUUPy material has a great contribution to achieve faster self-healing through reconstruction of hydrogen bonds and shortening self-healing time. Consequently, the initial mechanical properties of the severed PUUPy material are fully restored at lower temperatures with a faster self-healing time (80 °C, 1 h). The tensile strength and toughness of the PUUPy composite (5 wt % UPy) were increased by 12.82% (17.6 from 15.6 MPa of PU) and 91.6% (75.6 from 39.5 MJ m–3 of PU), respectively. For further obtaining high-strength self-healing polyurethane composites, hydroxylated boron nitride nanosheets (BNNS–OH) were introduced to PUUPy composites reforming an interface hydrogen bond, which can effectively transfer stress and enhance the strength of the PUUPy/BNNS–OH composites. The developed PUUPy/BNNS–OH (20 wt %) composite has significantly enhanced the tensile strength and toughness of the material to 24 MPa and 83.5 MJ m–3 and can lift the weight of 10,000 times its own weight after self-healing, showing its excellent mechanical properties. The heat transfer tube filled with the superstretchable, durable, and self-healing PUUPy/BNNS–OH composite placed on a 100 °C plate-type heater could reach a temperature difference of close to 40 °C compared to the commercial PU and Cu pad, which can be attributed to eliminating the interface thermal resistance caused by microbubbles. Therefore, its high strength, high toughness, and faster self-healing ability make it a promising candidate for further thermal management applications in portable electronics.