Effects of different activator systems on cure characteristics and physicomechanical properties of a NR/SBR blend

Abstract

Different activator systems containing zinc oxide, zinc stearate, calcium oxide, thiodiglycol metal complexes and nano-zinc oxide were applied for sulphur vulcanization of NR/SBR blend. The systems were chosen in order to have better dispersion in rubber matrix, better metal ion release in vulcanization process and lower zinc content. The cure characteristics and physicomechanical properties were investigated. Results showed that zinc oxide could be reduced from 4 to 2 phr in the formulation, without any detrimental effects on properties. Zinc stearate was not a good activator but it could be employed in combination with zinc oxide to improve tensile properties. Calcium oxide did not show satisfactory results. Zinc complex of thiodiglycol was an acceptable substitute for zinc oxide due to better dispersion in rubber matrix and better ability for zinc ion release. Zinc content could be reduced to about 4.5 mmol per 100 g of rubber by using this complex. Calcium complex of thiodiglycol was not a good choice either and showed detrimental effects on properties. Application of nano-zinc oxide did improve abrasion and tensile properties due to better surface effects. An alternative mixing method which was used to improve the zinc oxide and nano-zinc oxide dispersion was good and showed better abrasion and tensile properties. The results are presented as patterns to achieve the desirable properties.