Effects of Cross-Linking Modification by Castor Oil on Properties of Self-healing Polyurethane at Room Temperature

A series of self-healing polyurethane elastomers (PU) were synthesized using different amounts of castor oil (CTO) or trimethylolpropane (TMP) as cross-linking reagents. The effects of the amount of cross-linking reagent on the mechanical properties and self-healing properties of PU were investigated by an electronic tensile tester. The results showed that both CTO and TMP could increase the tensile strength of self-healed PU, but the elongation at break was decreased. Meanwhile, the self-healing properties of the elastomer were reduced. With an identical molar ratio of crosslinking reagent, the self-healing property of PU crosslinked by CTO was found to be superior to that crosslinked by TMP. The self-healing capacity of PU could only be maintained while a small amount of TMP was added. With the increase of CTO addition, the tensile strength of self-healed PU increased first and then decreased. When the molar ratio of polypropylene glycol (PPG) to CTO was 7∶3, the optimal overall performances were obtained, the tensile strength was recovered to 80.95% of the original level after self-healing.