The effect of sulfur to accelerator ratio on the adhesion strength of NR/SBR blend to bronze-plated bead wire in sulfur curing systems

The effect of sulfur-to-accelerator ratio was investigated in sulfur curing system on the adhesion strength of NR/SBR blend to bronze-coated bead wires. Two different amounts were applied for sulfur-to-accelerator ratio including 3.5 as conventional curing (CV) system and 1.28 as semi-efficient curing (SEV) system with two different amounts of carbon black loadings. Pull-out test revealed that the CV curing system increased the pull-out energy (87.23 kg-f) in comparison with SEV curing system (37.69 kg-f) in blend with 50 phr carbon black. For the compounds with 28 phr carbon black, this increase was also observed 1.7 fold. In samples with the same curing system, by changing the amount of carbon black from 28 phr to 50 phr, the pull-out energy enhanced more than 1.5 times for CV curing system, while this increment for SEV curing system was about 1.2 times. The compounds prepared via CV curing system have higher tensile strength and elastic modulus in both carbon black loadings in comparison to SEV curing system. The crosslinking density for the compounds with CV curing system is higher than the compounds with SEV curing system with the same carbon black contents.