Epoxy resins are among the best performing adhesives. Recovering the adhesively joined parts for repetitive use demands innovative bonding strategies to afford facile debonding while not sacrificing the adhesion performance. Here, a series of hardeners were prepared by reacting elemental sulfur with renewable 10-undecenoic acid and further employed for curing diglycidyl ether of bisphenol-A (DGEBA). Dynamically cross-linked epoxy networks from this solvent- and catalyst-free procedure exhibit high tensile strength and toughness, which are well maintained during repetitive thermal processing, assisted by exchanges of the S–S bonds and β-hydroxyl ester moieties. Moreover, the toughened epoxy resins show a high adhesion strength of up to 31 MPa for steel plates. Furthermore, the joined plates can be readily separated by immersing in a methanol solution of Na₂S or hexylamine without any residual resins.