Room-Temperature Vulcanization Time Controls Self-Crosslinking-Driven Self-Healing Behavior in Natural Rubber Sheets
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Abstract
This study investigated the preparation of natural rubber sheets with self-crosslinking-driven self-healing behavior under controlled curing conditions at room temperature. The work aimed to develop a simpler and more practical approach for producing recoverable rubber materials without complex chemical modification or external heating. Natural rubber sheets were prepared using a sulfur vulcanization casting process under different curing temperatures and curing times. The effects of curing conditions on network formation, swelling behavior, crosslink density, and mechanical recovery were evaluated. Fourier transform infrared spectroscopy was used to monitor changes in the chemical structure during vulcanization. The results showed that increasing curing temperature and curing time promoted sulfur crosslink formation within the rubber network. However, curing at 30 ± 5 oC preserved a greater amount of remaining unsaturated bonds and maintained lower crosslink density, which favored polymer-chain mobility during the healing process. The swelling analysis confirmed the gradual development of a denser network structure with increasing curing severity. Mechanical testing demonstrated progressive recovery of tensile properties after the damaged samples were rejoined and healed under room-temperature conditions. Healing efficiency increased continuously with healing time, indicating gradual interfacial recovery through continued network rearrangement and self-crosslinking reactions. The findings suggested that controlled room-temperature curing provided a suitable balance between crosslink formation and chain mobility, allowing recovery behavior to occur without additional external stimuli. This study demonstrated a simple and low-temperature strategy for preparing natural rubber sheets with recoverable mechanical performance and provided useful information for the future development of functional and sustainable rubber materials.
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