An alternative method for the vulcanization of rubber articles

Zinc oxide was treated with a sulfenamide accelerator by vacuum evaporation of a suspension of ZnO in a solution of the accelerator in dichloromethane to provide a convenient single material component to use as additive. The optimum quantity of the accelerator in the additive was found to be 350 mg/g. A large batch of the surface-modified zinc oxide with this composition (referred to as the ‘TBBS/ZnO powder’) was then prepared. The effect of an increasing loading of the TBBS/ZnO powder on the cure properties of ethylene-propylene-diene rubber (EPDM) and polybutadiene rubber (BR) containing elemental sulfur was subsequently measured. When the loading of the TBBS/ZnO powder in the rubbers was raised progressively, the scorch time was unaffected and the optimum cure time reduced. The rate of cure kept rising until it reached an optimum. The crosslink density increased substantially as the loading of the TBBS/ZnO powder in the rubber was raised progressively. All the indications are that the use of the TBBS/ZnO powder in combination with sulfur in the cure system improves efficiency of the vulcanization process, reduces cost and harmful effects while also shortening the cure cycle. The surface modified TBBS/ZnO powder is a viable alternative chemical additive for the sulfur vulcanization of rubber.