# Preparation and Chemical Protective Clothing Application of PVDF Based Sodium Sulfonate Membrane
## 3 Results
### Permeations and Selectivities of Membranes  
To prevent severe heat stress and the injury caused by it, the water vapor transfer rate (WVTR) should be above 2000 g m\({}^{-2}\) day\({}^{-1}\) in chemical protection clothing applications [5]. The sodium sulfonate groups in PVDF-\(g\)-SSS have a good affinity to water molecules, thus can provide hydrophilic pathways to promote water diffusion and improve the breathability of CPC. In this study, the water permeability was measured by ASTM E96-95 method. As shown in Figure 7 and Table 4, the water vapor transfer rate increased from 60 to 3668 g m\({}^{-2}\) day\({}^{-1}\) as the IEC increased from 0 to 2.29 mmol/g. Besides, an obvious leap in WVTR was observed from M3 to M4, which may be due to the formation of a continuous water transport channel at a higher content of SSS groups. The WVTR is also depicted in Table 4; M4, M5, and M6 with WVTR above 2000 can fulfill the requirement for CPC application [5]. Figure 6: Typical stress–strain curves of M1–M6 membranes. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Thickness (\(\mu\)m)** & **Strength (MPa)** & **Elongation-at-Break (\%)** \\ \hline M1 & 85 & 40.6 \(\pm\) 2.1 & 112.0 \(\pm\) 12.8 \\ M2 & 120 & 32.9 \(\pm\) 2.3 & 306.3 \(\pm\) 24.2 \\ M3 & 110 & 30.5 \(\pm\) 2.6 & 329.0 \(\pm\) 29.2 \\ M4 & 125 & 26.4 \(\pm\) 1.9 & 329.9 \(\pm\) 25.7 \\ M5 & 130 & 17.4 \(\pm\) 2.0 & 235.5 \(\pm\) 18.3 \\ M6 & 130 & 9.9 \(\pm\) 1.1 & 145.1 \(\pm\) 13.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The thickness and mechanical properties of PVDF-\(g\)-SSS membranes. The vapor permeation (VP) of dimethyl methyl phosphonate (DMMP, a simulant for nerve agents) was measure using the same method as WVTR, and the results are shown in Figure 8 and Table 4. A decreasing trend of DMMP vapor permeation was observed as IEC increases from 0 to 2.29 mmol g\({}^{-1}\). The selectivity between water vapor was calculated by S = VPwater/VP\({}_{\text{DMMP}}\). As shown in Figure 9, when the IEC is below 1 mmol/g, the selectivity increases gradually from 1.28 to 16.08. Significantly enhanced selectivity could be achieved when the IEC exceed 1.5 mmol g\({}^{-1}\), e.g., 118.35 at 1.95 mmol g\({}^{-1}\) and 150 at 2.29 mmol g\({}^{-1}\), which are higher than that of a polystyrene sulfonic acid membrane (80) and a sulfonated poly(styrene-isobutylene-styrene) membrane (35) [14; 19]. The vapor permeation of 2-chloroethyl phenyl sulfide (CEPS, a simulant for blister agents) was measured using the same method as DMMP, and the results are shown in Figure 8 and Table 4. A decreasing trend of CEPS vapor permeation similar to DMMP was observed with increasing IEC values. The selectivity between water vapor was calculated by S = VPwater/VP\({}_{\text{CEPS}}\). As shown in Figure 9, when the IEC is below 1 mmol g\({}^{-1}\), the selectivity increases gradually from 10.71 to 138.43. Significantly enhanced selectivity could be achieved when the IEC exceeds 1.5 mmol g\({}^{-1}\), e.g., 1975.69 at 1.95 mmol g\({}^{-1}\) and 3066.70 at 2.29 mmol g\({}^{-1}\), which are much higher than DMMP and also higher than that of a polystyrene sulfonic acid membrane (1500) and Nafion (400) [14].