Replacement of ZnO by ecofriendly synthesized MgO in the NBR vulcanization

Rubber compounds contain several additives besides the elastomer matrix, such as fillers, curing agents, activators, antioxidants, among others. However, some of these additives causes a negative impact on the environment, e.g., zinc oxide commonly used as activator in the vulcanization process. Thus, in this study, ecofriendly synthesized magnesium oxide was evaluated as substitute to ZnO in a standard nitrile rubber composition. Additionally, commercial magnesium oxide was also included in study to be used as a reference. All rubber compounds were evaluated in terms of rheometric (minimum and maximum torques, curing times), rheological (dynamic moduli), and mechanical (tear resistance, tensile resistance, hardness, and stress relaxation) properties and crosslink density. The marching-modulus was more noticeable when MgO and green-MgO was employed as activator. The vulcanization of NBR with MgO and green-MgO resulted in rubber materials with higher crosslink density, higher elastic moduli, lower phase angle δ, and lower stress relaxation than ZnO composites. Besides that, no significant difference was observed for the mechanical performance regarding tear strength, tensile strength, and hardness.