Investigating the Effect of Curing Activators on the Cure Kinetics of Acrylonitrile-Butadiene Rubber Filled with Graphene Oxide and Reduced Graphene Oxides Nanocomposites

For the first time, acrylonitrile-butadiene rubber (NBR)-graphene oxide (GO) and reduced graphene oxide (rGO) composites were prepared without cure activators: zinc oxide/stearic acid (ZnO/SA) and studied. The vulcanization characteristics of the compounds were systematically studied at 160-190 degrees C, with the aid of rheometer and differential scanning calorimetry (DSC) techniques. NBR revealed rapid curing time (t(90)) with greater cure rate index compared with NBR-GO/rGO composites for the rheometer measurement. This results were in correspondence with the activation energies E-a (kJ/mol) calculated by Ozawa and Kissinger models of vulcanization kinetics. NBR-rGO obtained reduced t(90) and E-a (kJ/mol) than NBR-GO, perhaps due to lower oxygenated groups: epoxide (-C-O-C-), carboxyl (-O-C=O), and hydroxyl (-OH) present. Although, the composites delayed in curing, they significantly recorded high tensile properties with high reinforcing factors than NBR. The order of increasing mechanical properties: NBR < NBR-rGO < NBR-GO followed the same order of increasing crosslinking density. In terms of tensile strength, NBR-GO-1 obtained 62.5% and 18.2% increment than NBR and NBR-rGO-1, respectively. The findings from this study indicate that the absence of ZnO/SA in rubber compounds may slow down curing of rubber-GO/rGO composites and lower networks compared with those containing activators ZnO/SA. However, optimization of ZnO/SA and with desired functional groups on graphene and derivative graphene sheets (GDS) including other proposed factors may enhance the curing speed of rubber-GDS based systems, without compromising their mechanical integrity for advanced applications.