Thermoreversible Behavior of Castor Oil‐Based Polyurethane Vitrimer Under Different Dynamic Covalent Networks

ABSTRACT Recycling thermosets is essential for environmental protection and the sustainable development of a circular economy. Among various approaches, dynamic chemistry has proven to be an effective solution for recycling thermosetting polymers. To improve the sustainability of thermosetting polyurethanes and investigate their thermoreversible behavior with different combinations of disulfide bonds and Diels–Alder bonds, this study developed castor oil‐based polyurethane vitrimer (Co‐PUV 1/Co‐PUV 2/Co‐PUV 3) with varying dynamic covalent networks. The chemical structure, dynamic reversible reactions, rheological characteristics, and thermal‐responsive self‐healing were analyzed. The results revealed that disulfide bonds, combined with Diels–Alder bonds, can significantly enhance the thermoreversible response of the crosslinked networks. The first‐rank combination was found in Co‐PUV 2, which contained Diels–Alder bonds and 4.22 mol% disulfide bonds. This sample exhibited the shortest stress relaxation time and the largest creep range between 60°C and 100°C. Additionally, Co‐PUV 2 achieved an 84.4% recovery rate of mechanical properties at 85°C and 0.3 MPa and regained its melt‐recyclability at 135°C. In general, this work provides insights into the influence of disulfide and Diels–Alder bonds on the thermoreversible behavior of castor oil‐based polyurethane vitrimer, enlightening a foundation for the design of recyclable polyurethane using a multi‐dynamic bond strategy.