Abstract:
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°
C, with the aid of rheometer and differential scanning calorimetry (DSC)
techniques. NBR revealed rapid curing time (t90) with greater cure rate index compared with NBR–GO/rGO composites for
the rheometer measurement. This results were in correspondence with the activation energies Ea (kJ/mol) calculated by Ozawa
and Kissinger models of vulcanization kinetics. NBR–rGO obtained reduced t90 and Ea (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.
