Effect of reduced graphene oxide and maleic anhydride compatibilization on the curing, morphological, and pre-/post-aging mechanical properties of EPDM/NBR blends

This study investigates the development of elastomeric composites based on ethylene-propylene-diene monomer (EPDM) and nitrile-butadiene rubber (NBR) reinforced with reduced graphene oxide (rGO). Given the limited literature on the combined use of rGO and compatibilizing agents in EPDM/NBR systems, this research focused on the effect of a maleic anhydride-grafted ethylene elastomer (E–g-MA) in EPDM, NBR and a 70/30 EPDM/NBR blend prepared using two-roll mill mixing. The rGO was characterized through X-ray diffraction, scanning electron microscopy (SEM) with quantitative energy-dispersive X-ray spectroscopy and thermogravimetric analysis, while the elastomer compounds were evaluated for cure characteristics, morphology, chemical resistance and mechanical properties before and after accelerated aging. SEM micrographs revealed that the combination of E–g-MA and rGO reduced the number of pull-out voids and produced a more homogeneous fracture surface in EPDM and in the EPDM/NBR blend. At higher E–g-MA and rGO content (1 phr), tensile strength improved 127% for EPDM and 81% for the blend, and the elongation at break of EPDM increased from 216 to 490%. Welch's ANOVA with Games-Howell post-hoc tests (α = 0.05) confirmed that these differences are statistically significant. For NBR, neither additive significantly changed the tensile properties, although 1 phr of rGO reduced the volume change in propanone from 70 to 41%. After accelerated aging, EPDM/NBR/1E-g-MA/1rGO reached a tensile strength of 5.1 MPa, compared with 2.2 MPa for the neat blend. This composite also showed a lower volume change than the neat blend after immersion (16% versus 31% in propanone and 194% versus 229% in fuel oil), whereas EPDM/1E-g-MA/1rGO showed increased swelling in propanone. These findings indicate that combining rGO and E–g-MA is an effective strategy for improving the strength and aging behavior of EPDM/NBR composites, although the reduced resistance of EPDM to polar solvents at the highest loading should be considered.