# Preparation Methods and Properties of CNT/CF/G Carbon-Based Nano-Conductive Silicone Rubber
## 3 Results and Discussion
### Properties of the PREPARED Single-Filler Conductive Silicone Rubbers
(a) Electrical properties of graphene conductive silicone rubber  
The volume resistivity and surface resistance of LSR/G with different graphene concentrations are shown in Figure 5 and Table 4.  
Figure 4: Thermogravimetric analysis of (**a**) LSR/LSR + 7.5 wt% CF; (**b**) LSR + 7.5 wt% CF; (**c**) pure LSR. As shown in Figure 5, when the graphene filling amount was 1.5-4.5 wt%, under the condition of less graphene filling, no conductive path formed in the matrix, showing good insulation. When the graphene filling amount reaches 5.5 wt%, the volume resistivity is 8.72 \(\times\) 10\({}^{4}\)\(\Omega\)-cm, and the surface resistance is 2.48 \(\times\) 10\({}^{6}\)\(\Omega\). The filling amount of graphene was moderate and the conductive particles were in contact with each other, which enabled the formation of conductive paths and greatly improved the conductivity. When the graphene content exceeded 5.5 wt%, the volume resistivity and surface resistance sharply decreased and the conductivity was unstable. The volume resistivity of boron nitride-multilayer graphene/silicone rubber (BN-MG/SR) prepared by the literature [24] is as high as 4 \(\times\) 10\({}^{11}\)\(\Omega\)-cm, which is higher than that of the 5.5 wt% graphene conductive silicone rubber prepared in this paper. The ratio (8.7 \(\times\) 10\({}^{4}\)\(\Omega\)-cm) is 7 orders of magnitude higher, which shows that the graphene conductive silicone rubber prepared in this paper has better electrical properties. In the concentration range of 4.5-5.5 wt%, graphene particles considerably influence the electrical properties of silicone rubber, and the best electrical properties of LSR/G are observed in this range. (b) Mechanical properties of LSR/G  
The tensile strength, elongation at break, and elastic modulus of LSR/G are shown in Figure 6 and Table 5.  
As can be seen from Figure 6, when the mass fraction of graphene is 1.5 wt%, the tensile strength of the prepared conductive silicone rubber is 1.26387 Mpa. When the mass fraction of graphene is 1.5-4.5 wt%, the tensile strength, elongation at break, and elastic modulus of the prepared conductive silicone rubber decrease rapidly. When the mass fraction of graphene is in the range of 4.5-5.5 wt%, the changes of tensile strength, elongation at break, and elastic modulus of the prepared conductive silicone rubber are relatively stable. When the mass fraction of graphene is 5.5 wt%, the tensile strength, elongation at break, and elastic modulus of conductive silicone rubber are 0.07479 Mpa, 67.3561%, and 0.18089 Mpa, respectively. As the graphene content was further increased, the tensile strength obviously decreased and the elongation at break and elastic modulus slowly decreased. In the LSR/G experiments, the mechanical properties of graphene rapidly decreased due to the self-lubrication between molecules. To ensure the mechanical properties of LSR/G, the graphene concentration of 4.5-5.5 wt% was determined to be ideal, and within this range, the conductive silicone rubber formed a conductive network. The graphene-filled silicone rubber prepared by the literature [25] has a maximum tensile strength of 1 Mpa, which is lower than that of the graphene conductive silicone rubber prepared in this paper (1.26387 Mpa), which proves that the graphene conductive silicone rubber prepared in this paper has good mechanical properties. Analysis of dispersibility and heat resistance of LSR/G. The electrical conductivity of LSR/G increased with the graphene content, and the resistance value considerably changed in the graphene concentration range of 4.5-5.5 wt%. The composite properties of LSR/G with 5.5 wt% graphene were tested and analyzed. Dispersion analysis  
Figure 7 displays the Raman spectra of LSR/G. The bending peak at 1340 cm\({}^{-1}\) and the -CH2 stretching vibration characteristic peak at 2899 cm\({}^{-1}\) were not detected for LSR/G. This proves that graphene can be well combined with silicone rubber substrate. Figure 6: Mechanical properties of graphene with different concentrations.