## 3 Results and Discussion
### Electrical Conductivity  
The electrical conductivity of the material is one of the important factors influencing its EMR shielding. Usually, in order to evaluate the electrical conductivity of the textile material, inverse dimension--surface resistivity is measured. For determination of this parameter there was used standard test method EN 1149-1 [40], which is mostly applicable for textile materials intended for protective clothing. The surface resistivity (\(\rho\), \(\Omega\)) measurement results presented in Table 4 show that before washing all tested materials are possessed of near the same electrical conductivity, despite they are treated with plasma or not. After washing procedures, the surface resistivity of samples slightly increased, \(\rho\) increased by one row, which means that the conductivity rather decreased. In this case also there was no marked differences between plasma treated and untreated samples, maybe except for samples from PA/cotton fibers (S3C and S3 PC), where a positive plasma treatment influence can be noticed.  
However, after analysis of the correlation between the surface resistivity of tested samples and EMR shielding effectiveness SE (dB) (Figure 5) was assessed, that knowledge of the surface resistivity, determined by the method used could not be used for the prediction of sample shielding ability. The coefficients of determination R\({}^{2}\) = 0.2547 (Figure 5a) and R\({}^{2}\) = 0.131 (Figure 5b) for the dependence of SE on the surface resistivity of samples before and after washing, respectively, shows that a correlation between these parameters is rather weak.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Group of Samples**} & \multirow{2}{*}{**Code of Sample**} & \multirow{2}{*}{
\begin{tabular}{c} **Surface Resistivity** \\ \(\rho\), \(\Omega\) \\ \end{tabular} } & \multicolumn{2}{c}{**Surface Resistivity**} \\  & & & **\({}^{\bullet}\)After Washing** \\ \hline \multirow{2}{*}{**I**} & S1C & \(2.1\times 10^{7}\) & \(1.7\times 10^{8}\) \\  & S1 PC & \(2.3\times 10^{7}\) & \(2.6\times 10^{8}\) \\ \hline \multirow{2}{*}{**II**} & S2C & \(1.7\times 10^{7}\) & \(4.3\times 10^{8}\) \\  & S2 PC & \(4.4\times 10^{7}\) & \(3.3\times 10^{8}\) \\ \hline \multirow{2}{*}{**III**} & S3C & \(8.7\times 10^{7}\) & \(2.1\times 10^{8}\) \\  & S3 PC & \(3.7\times 10^{7}\) & \(4.5\times 10^{8}\) \\ \hline \multirow{2}{*}{**IV**} & S4C & \(1.5\times 10^{7}\) & \(1.0\times 10^{8}\) \\  & S4 PC & \(5.6\times 10^{7}\) & \(3.7\times 10^{8}\) \\ \hline \hline \end{tabular}  
* The evaluated expanded uncertainty (U) for surface resistivity (\(\rho\)) measurement U = \(\rho\).0.12 [\(\Omega\)]: The reported expanded uncertainties are based on a standard uncertainty multiplied by a coverage factor k = 2, which for a normal distribution provides a level of confidence of approximately 95%.  
\end{table}
Table 4: The electrostatic properties of investigated fabrics.  
Figure 5: _Cont._It stands to reason that results of \(\rho\) measurements, obtained for conductive paste coated samples with non-indiscrete surfaces (Figure 5), are not reliable and repeatable due to the method used, which does not exclude contact resistance in the system. The SEM images (Figure 6) illustrate that the surface of the coated side of fabric is not even and homogenous.  
Therefore, obtained \(\rho\) values only show that applied conductive coating provides the fabrics with electrical properties, but does not allow objectively to distinguish the differences between samples and to predict their shielding ability.  
Figure 5: Dependence of surface resistivity on shielding effectiveness: (**a**) unwashed samples; (**b**) samples after washing.  
Figure 6: SEM images of samples coated with conductive paste.