## 3 Results and Discussion
### EMI Shielding Effectiveness of Conductive Fabrics  
The four types of fabrics all demonstrate an EMI SE that is highly dependent on whether the metallic wires and fabrics build a complete shielding network. Furthermore, the employment of superhydrophobic treatment has a positive influence on the EMI SE. When composed of a higher density, the fabrics have a smaller porosity and greater EMI SE [30; 31]. After the superhydrophobic treatment, the fabrics are enwrapped in transparent films that decrease the distance among fibers to a certain extent and thus strengthens the EMI SE of the conductive fabrics. Figure 5 shows that when both the warp and weft yarns are composed of conductive wrapped yarns, the conductive fabrics exhibit a higher EMI SE comparing to those composed of conductive wrapped yarns as weft yarns. In particularly, PSA-SS-1, PSA-SS-2, PSA-SS-1', and PSA-SS-2' have EMI SE values of 33.26, 32.50, 34.08, and 34.42 dB at frequencies of 0-3000 MHz respectively, which refers to a 99% shielding effectiveness, suggesting that the conductive fabrics have a good EMI SE. Especially at 1000-2500 MHz, the fabrics have EMI SE of 30-50 dB. Furthermore, the number of metallic wires only has a marginal influence on the EMI SE because EMI SE is primarily related to a well-established shielding network.  
The shielding materials that suit the majority of electronic products are required to be able to shield incident electromagnetic waves between 30 and 1000 MHz, and an EMI SE of 35 dB is deemed to effectively block electromagnetic waves. Accordingly, the proposed conductive fabrics are also suitable for industry and commercial electronic equipment. With PSA roving as warp yarns, the conductive fabrics have an average EMI SE lower than 10 dB, indicating a low EMI SE. Although the difference in both of the number of laminations as well as lamination angle is helpful to the EMI SE, it also increases the thickness of the fabrics which is detrimental to the specific shielding effectiveness (SSE, the SE per unit volume). The EMI SE is based on the formation of a shielding network that is formed in the conductive fabrics. Using conductive yarns as both the warp and weft yarns can build a complete shielding network and yields a good shielding effect. If the conductive fabrics only have conductive yarns as the weft yarns, the absence of a shielding network leads to a low EMI SE.  
Figure 4: The breaking strength of conductive wrapped yarns as related to the twist counts. (**a**) one metallic wire; (**b**) two metallic wires.  
To further demonstrate the highly efficient EMI shielding of the conductive composite fabrics, the shielding effectiveness per unit volume (SSE) and specific SSE/t of the fabric based EMI shielding material are discussed in Figure 5d and Table 2[31; 32]. It can be found that the PSA-SS-1\({}^{\prime}\) and PSA-SS-2\({}^{\prime}\) superhydrophobic and conductive composite fabric in this study possesses a very high SSE/t (1623 dB-cm\({}^{2}\)/g and 1617 dB-cm\({}^{2}\)/g). The SSE value of the conductive fabric is related to the thickness of the fabric, the density of the fabric, and the total dB value. The larger the SSE value, the better the shielding effect.