storage modulus is approximately 1000 times greater than that of NR. The incorporation of CF into NR therefore increases the
modulus of NR composites. The extent of such increase depends on filler concentration, filler particle size, filler shape, and
filler–matrix interactions. Glass transition temperatures (Fig. 10) defined by G00 show a trend to shift to higher temperatures
as the filler concentration increased, indicating a greater immobilization of polymer chains by the filler particles. To characterize
the CF reinforcement effect in NR, reinforcement factor defined by the shear modulus of a NR composites normalized
by the elastic modulus of the NR matrix is fitted with Halpin–Tsai model that describes the anisotropic effect of filler in a
matrix. The experimental data and model fitting are shown in Fig. 11 for the hydrolyzed CF, CF, and oxidized CF. Halpin–Tsai
model [21] is described by the Eqs. (2)–(4).