Experimental Study on the Curing Process of Styrene-Butadiene-Rubber

Abstract

This is the second paper of a series that describes the curing process of styrene-butadiene-rubber packed in a cylindrical mold with inner diameter of 74.6 mm. Present paper mainly describes the curing process under the mold cooling stage. Sulfur was used as the curing agent and the sulfur concentration ranged from 1.0 to 5.0 weight percent. The mold temperature was controlled in two stages. The mold was heated at 414 K for 45 min. then switched off, and the mold was cooled by natural convection to the surroundings up to 75 min. Time-dependent radial distributions of the temperature profile and the crosslink density were measured in the cooling stage. It was confirmed that the curing reaction was related strongly to the temperature field. In the cooling stage, rubber temperature decreased in the outer zone whereas overshooted in the inner zone. The degree of cure at the rubber center reached to around 0.8 at time 45-60 min. elapsed after taking the heater off for sulfur concentration of 1 and 3 weight percent.