Investigation of the Coupled Effect of Liquid and Solid Inorganic Additives on Thermal Stability and Water Retention of PFSA Composite

Here, investigation of the high-temperature water retention property of new composites, which contain perfluorosulfonic acid (PFSA) polymer as matrix, a mineral acid, and MgF 2 nanoparticles as inorganic additives, is done based on structural analysis. The composite shows an improvement in the water removal temperature from 50 to 250 °C because the crystalline water molecules were attached on the surface of solid inorganic additives at 250 °C. To optimize the water retention property, the 1 wt % of sulfuric acid and 3–15 wt % of MgF 2 -coated glass particles in PFSA polymer composites as additives were investigated. From the Fourier transform infrared-attenuated total reflection studies of these composite membranes, two major phenomena related to structural details of PFSA polymer as a function of the polymer and the weight ratio of the solid additives are observed: (1) sulfonic acid group released the proton even with low humidity and (2) the conformation and/or the degree of the crystallinity of the poly(tetrafluoroethylene) hydrophilic domains change in the membrane. It is found that the sulfuric acid connects the sulfonic acid groups of the polymer and MgF 2 nanoparticles, coated on the surface of acidic glass particles, by direct bonding among them.