Cure and dynamic mechanical properties in peroxide-cured isoprene rubber: effects of stearic acid and amine-based antioxidant

Peroxide-cured isoprene rubber with various amounts of stearic acid and N-isopropyl-N′-phenyl-p-phenylenediamine (i-PPD) was prepared. Processability, cure and dynamic mechanical properties of compounds were investigated. It has been found that stearic acid affects only the uncured compounds in terms of processability by acting as a lubricant, and plays no significant role in curing and dynamic mechanical properties. By contrast, i-PPD as an amine-based antioxidant shows pronounced effect on processability, cure and dynamic mechanical properties. The addition of i-PPD up to 2 phr could increase Mooney viscosity due to a thermal stabilization during high shear mixing. Exceeding this concentration, i-PPD shows plasticizing effect leading to a decrease in Mooney viscosity. Additionally, it has been shown that the addition of i-PPD reduces the crosslink density affecting remarkably the dynamic mechanical properties of compounds.