EFFECT OF BENZOTHIAZOLOYLTHIAZOLES AS SECONDARY ACCELERATORS IN THE SULFUR VULCANIZATION OF NATURAL RUBBER

The vulcanization of natural rubber and a blend of natural rubber and reclaimed rubber by using binary accelerator systems containing a novel series of benzothiazoloylthiazole as secondary accelerator (SA) has been studied. These secondary accelerators were synthesized by a green chemical method under solvent-free conditions, by the irradiation of microwaves (180 W). The synergistic effect of the SA with N-Cyclohexyl-2-benzothiazolsulfenamide as primary accelerator was studied at 150 °C. These binary systems were effective in reducing the cure time and improving the rheometric and mechanical properties. These SAs were found to be effective in reducing the cure time with a minimal amount of 0.5 phr, but commercially available SAs such as thioureas and tetramethylthiuram disulfide were reported to show reduction in cure time only by increasing the amount of SA. Mechanical properties such as hardness, abrasion loss, tensile strength, percentage strain at break, and modulus at different elongations 100, 200, and 300% were evaluated and found to be immensely improved. The improved mechanical properties were also shown to be at par with crosslink densities (1/2Mc) of different mixes.