Castor oil-segmented polyurethanes with disulfide bonds: excellent self-healing and mechanical properties

Self-healing polyurethanes are garnering attention as a smart material, and has significant application potential in aerospace, biomedical, and electronics fields. In this paper, castor oil is selected as a soft segment in place of petroleum-based polyol to enhance the mechanical properties of polyurethane while improving the mobility of molecular chains. Meanwhile, a polyurethane with good self-healing properties was successfully prepared by selecting 2,2`-Diaminodiphenyl disulfide (DTDA) containing disulfide bonds as a chain extender. As the proportion of DTDA increases, the initial thermal decomposition temperature of polyurethane decreases by 21°C. Cutting and tensile tests confirmed the high mechanical properties and self-healing characteristics of the polyurethane network. And the self-healing efficiency of the polyurethane materials was improved by prolonging the healing time and increasing the healing temperature. As the content of disulfide bonds and hard segments increased, the tensile strength of polyurethane increases progressively, the elongation at break decreased, and the R(stress) and R(strain) of each specimen tended to increase and then decrease. The healing efficiency of the specimen with a disulfide bond content of 13.45% was optimal, with both R(stress) and R(strain) reaching more than 99%.