Self-healing efficiency of natural rubber vulcanizates depending on crosslinking density

Copper chloride (CuCl 2 ) is used in sulfur-cured natural rubber (NR) to regulate disulfide exchange reaction in self-healing process while factors influencing the healing capability remain unclear. Herein CuCl 2 and other additives including zinc oxide and sulfur are used to mediate self-healing efficiency of NR vulcanizates. For revealing the role of proteins and phospholipids in NR, the mediated self-healing capability is compared with sulfur-cured isoprene rubber (IR) vulcanizates. The results reveal that CuCl 2 interferes rheological responses and vulcanization dynamics in both rubbers, and it causes intermolecular disassociation in NR gums. As self-healing capability is closely related to crosslinking density, formulation is adjusted to balance healing efficiency and tensile strength. Healing efficiency of around 70% and the highest tensile strength of about 6 MPa are achieved at crosslinking density about 70 mol/m 3 when vulcanizates are healed at 140°C for 30 min. Graphical