The mechanical properties of the nanocomposites of NR with
TRGO dispersed in SDS or Pluronic F 127 with nanoparticle concentrations
between 1 and 4 phr are shown in Table 1. In order to evaluate
the effect of the surfactants on the mechanical properties of
NR, dispersions of NR in both surfactants without graphene were
also prepared. The incorporation of SDS does not significantly
affect the elastic modulus, E100, E300 and E500, however, produces
a strong decrease of the maximum strength of NR. This is
due to the fact that at high SDS concentrations, SDS aggregates
are formed which promote the formation of defects in the interstices
of the NR particles [24]. Meanwhile, the addition of Pluronic
F127 as surfactant produces a marked decrease in the properties of
the NR, indicating that the Pluronic behaves as a plasticizer, giving
rise to the coalescence of NR particles [25]. It can be seen that
regardless of the surfactant used for the aqueous dispersion of
graphene, the TRGO effectively acts as a reinforcing agent of NR
resulting in a substantial increase in both the elastic modulus
(expressed as stress at various strains) and the maximum strength.
This behavior gradually increases with the concentration of TRGO
in the nanocomposite. Importantly, this improved material
strength is achieved without drastically affect the elastic properties
of the material.