# 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  
(1) Properties of the CF conductive silicone rubber  
CF conductive silicone rubber (LSR/CF) was prepared by varying the CF content to 1.5, 3.5, 5.5, 7.5, 8.5, 10.5, 11.5, 15, and 25 wt%, and the ratio of silicone rubber to n-heptane was kept unchanged at 1:2. The properties of LSR/CF were analyzed. (a) Electrical properties of the CF conductive silicone rubber  
The volume resistivity and surface resistance curves of LSR/CF with different CF concentrations are shown in Figure 1 and Table 2.  
As shown in Figure 1, the volume resistivity and surface resistance of LSR/CF sharply decreased when the CF content was increased from 1.5 to 5.5 wt%. When the CF content was 5.5 wt%, the volume resistivity was 1.5 \(\times\) 10\({}^{5}\)\(\Omega\)-cm, the surface resistance was 7.5 \(\times\) 10\({}^{5}\)\(\Omega\), and the conductive path began to form. When the CF content was 7.5 wt%, the volume resistivity was 9.5 \(\times\) 10\({}^{4}\)\(\Omega\) cm and the surface resistance was 2.88 \(\times\) 10\({}^{5}\)\(\Omega\). Moreover, the CF filling amount was moderate, and the particles had a great chance of contacting each other, which enabled the formation of a conductive path and greatly improved the conductivity. When the CF content exceeded 7.5 wt%, the volume resistivity and surface resistance  
\begin{table}
\begin{tabular}{c|c c} \hline
**Carbon Fiber Content** & **Volume Resistivity** & **Surface Resistance** \\
**wt\%** & \(\Omega\)-cm** & \(\Omega\) \\ \hline
1.5 & 2.5 \(\times\) 10\({}^{11}\) & 7.6 \(\times\) 10\({}^{12}\) \\
3.5 & 1.8 \(\times\) 10\({}^{9}\) & 5.4 \(\times\) 10\({}^{10}\) \\
5.5 &  
rapidly decreased. The results show that CF particles have a considerable influence on the electrical properties of silicone rubber. When the CF concentration was increased from 5.5 to 7.5 wt%, the volume resistivity and surface resistance of LSR/CF slowly decreased and tended to stabilize, and the electrical properties of CF conductive silicone rubber were stable. The volume resistivity of carbon fiber/(boron nitride/silicone rubber) (CF/(BN/SR)) composites studied in reference [20] is 8.6 \(\times\) 10\({}^{13}\)\(\Omega\) cm, which is 9 orders of magnitude higher than the volume resistivity of 7.5 wt% carbon fiber conductive silicone rubber (9.5 \(\times\) 10\({}^{4}\)\(\Omega\)-cm) in this paper, which indicates that the carbon fiber conductive silicone rubber prepared in this paper has good electrical properties. The above analysis shows that the conductive properties of LSR/CF become stronger with increasing CF concentration. Furthermore, for the mass ratio of 5.5-7.5 wt%, the electrical properties of CF conductive silicone rubber were good. (b) Mechanical properties of the CF conductive silicone rubber  
The tensile strength, elongation at break, and elastic modulus of LSR/CF with different CF concentrations are shown in Figure 2 and Table 3.  
The figure shows that, as the CF concentration increases, the mechanical properties generally rapidly decline first and then slowly decline. [PERSON] et al. [21] found that adding too much carbon fiber would reduce the mechanical properties of composites. In this paper, when the carbon fiber content is 1.5 wt%, the tensile properties of conductive silicone rubber are the best, with tensile strength of 2.81 Mpa, elongation at break of 111.3%, and elastic modulus of 0.67 MPa. When the CF concentration was increased from 1.5 to 5.5 wt%, the mechanical properties of the conductive silicone rubber rapidly decreased, because part of the CF filler mixed with LSR to yield the conductive silicone rubber and another part precipitated to the lower layer of the mixed solution in the molding preparation stage to form a CF-like conductive film. The mechanical properties of LSR/CF improved when the CF content was increased from 5.5 to 7.5 wt%; the tensile strength exceeded 2 MPa and the elastic modulus exceeded 0.4 MPa. [PERSON] et al.