REACTIVE COMPOUNDS FOR EFFECTIVE UTILIZATION OF SILICA

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS), diisopropyl thiophosphoryl-N-oxydiethylene sulfenamide (DIPTOS), diisopropyl thiophosphoryl-N-oxydiethylene disulfide (DIPTOD), diisopropyl thiophosphoryl-2-benzothiazole monosulfide (DIBMS), diisopropyl thiophosphoryl-2-benzothiazole disulfide (DIBDS) and bis(diisopropyl)thiophosphoryl monosulfide (DIPMS) react with silica and generate isopropyl alcohol as a result of rubber-DIPDIS-silica interactions. Increasing the amount of DIPDIS in the system brings about a corresponding increase in silica-rubber coupling, resulting in enhancement of Delta T-f - Delta T-f modulus and tensile strength, The vulcanizates containing 14 mmol DIPDIS and 35 phr of silica exhibit highest torque and tensile strength. This is commensurate with the optimum loading derived from Lee's method. The synergistic system containing DIPDIS and N-oxydiethylene-2-benzothinzole sulfenamide (OPTS) provides a very useful combination of accelerators. The vulcanizates obtained from this system exhibit highest torque and tensile value even at a lower concentration of accelerator (DIPDIS:OBTS = 7:3.5) far the same loading of silica (35 phr).