Sulfur vulcanization of oil-extended ethylene-propylene-diene elastomers at elevated temperatures

The kinetics of vulcanization of ethylene-propylene-diene elastomers at 403-463 K, depending on the sulfur and oil contents, were studied. The kinetic curves had the S-shaped pattern. During vulcanization at 463 K, reversion was observed regardless of the sulfur and oil contents, the induction period τ ind at this temperature was independent of the sulfur content, and τ ind increased with an increase in the amount of oil. The temperature coefficients of the induction period and maximum rate for the oil-extended and the oil-free elastomer were calculated using the Arrhenius equation. The vulcanization reaction rate order in sulfur depends on the elastomer type. The limiting crosslink density increased with an increase in the sulfur content and decreased with an increase in the oil content. Due to reversion, the limiting crosslink density at 463 K for all elastomers examined was lower than that at lower temperatures. The mechanism of vulcanization of oil-extended elastomers is discussed.