Natural rubber (NR) foams reinforced by a physical hybrid of nanographene/carbon
nanotubes were fabricated using a two-roll mill and compression molding process. The effects of
nanographene (GNS) and carbon nanotubes (CNT) were investigated on the curing behavior, foam
morphology, and mechanical and thermal properties of the NR nanocomposite foams. Microscope
investigations showed that the GNS/CNT hybrid fillers acted as nucleation agents and increased the
cell density and decreased the cell size and wall thickness. Simultaneously, the cell size distribution
became narrower, containing more uniform multiple closed-cell pores. The rheometric results showed
that the GNS/CNT hybrids accelerated the curing process and decreased the scorch time from 6.81 to
5.08 min and the curing time from 14.3 to 11.12 min. Other results showed that the GNS/CNT hybrid
improved the foam’s curing behavior. The degradation temperature of the nanocomposites at 5 wt.%
and 50 wt.% weight loss increased from 407 ◦C to 414 ◦C and from 339 ◦C to 346 ◦C, respectively,
and the residual ash increased from 5.7 wt.% to 12.23 wt.% with increasing hybrid nanofiller content.
As the amount of the GNS/CNT hybrids increased in the rubber matrix, the modulus also increased,
and the Tg increased slightly from −45.77 ◦C to −38.69 ◦C. The mechanical properties of the NR
nanocomposite foams, including the hardness, resilience, and compression, were also improved by
incorporating GNS/CNT hybrid fillers. Overall, the incorporation of the nano hybrid fillers elevated
the desirable properties of the rubber foam.