Role of supercritical carbon dioxide for selective impregnation of decrosslinking reagent into isoprene rubber vulcanizate

The behavior of supercritical CO₂ (scCO₂)/low molar mass molecule/crosslinked rubber ternary system was investigated in relation to the impregnation of reagent into the isoprene rubber (IR) vulcanizates, which was the first step of new decrosslinking reaction. The diffusion coefficient of decrosslinking reagent, diphenyl disulfide (DD), into the IR network in scCO₂ was 3.2×10⁻¹¹ m²/s. The distribution coefficient (K_c) of DD between the solvent and IR matrix was also determined for scCO₂ and toluene. The K_c for scCO₂ was higher about four orders of magnitude than that for toluene. DD was uniformly dispersed in the crosslinked IR matrix under 10 MPa at 313 K in scCO₂. These phenomena are advantages of use of scCO₂ for the effective decrosslinking reaction of IR vulcanizate.