Enhancing the Properties of Styrene-Butadiene Rubber by Adding Borax Particles of Different Sizes

In this research study, borax particles with different average sizes (1.25, 0.75, 0.60 μ m) were added to a styrene-butadiene rubber compound for reinforcement. This rubber has low mechanical, thermal, and surface properties, as well as low resistance to organic solvents. A laboratory two-roll mill was used at room temperature to add the borax particles to the synthetic rubber, then the rheometer characteristics such as torque, scorch time, and cure time were limited at a temperature of 150°C. The results showed that the torque and CRI (curing rate index) improved by 160% for torque and 600% for CRI respectively, dependent on reducing the particle size from 1.25 μm to 0.6 μm. The surface properties shown by FE-SEM, AFM images, and FT-IR analysis indicated a good dispersion of borax particles with an absence of the aggregates when a low borax particle size of 0.6 μm was used. Furthermore, the properties of tensile strength, elongation at break, and the hardness of the rubber compound were improved by 220% for tensile strength, 37% for hardness, and the reduction in elongation at break improved by 25% depending on the reduction in particle size. On the other hand, the resistance of the rubber compound to flame improved, besides the improvement of the thermal conductivity with decreasing particle sizes. The resistance of the rubber compound to organic solvents, such as toluene, was also improved, which was represented by the properties of swelling, the percentage of swelling index, and the cross-link density with 1.07% for swelling index and 1.3×10-3 mole/cm3 for cross-link density.