Simulation and verification for sulfur accelerated vulcanization of gum natural rubber compound

A simplified and realistic kinetic scheme was proposed for the cure reversion mechanism of accelerated sulfur vulcanization for gum natural rubber (NR) compounds, The vulcametric curves at different temperatures were simulated from curing to overcuring periods by using a kinetic approach. The different rate constants and activation energies were calculated from the simulation process. The simulated results showed a good agreement with isothermal vulcametric data over a wide range of temperatures and showed that the relationships between the rate constants and the cure temperatures were in accordance with the Arrhenius Equation. The activation energies (E-a1, E-a2, and E-a3) of the formation, desulfurization and decomposition of polysulfidic crosslink obtained from Arrhenius plots were 79.5, 102.6 and 138.8 kJ/mol, respectively. The experimentally measured crosslink densities determined by using swelling equilibrium and chemical probe techniques agreed with the simulated vulcametric curves to some extent.