Preparation And Properties Of Phosphorylated And Cross-linked EVOH/(Bis-A)-epoxy Resin Proton Exchange Membranes

It is the goal of the designed proton exchange membranes (PEM) that can keep high proton conductivity under low humidity than Nafion(?), can be commercialized at the same time to have the most PEM properties, and can low the PEM cost. Usually, the development of the PEM is to functionalize membrane with the acid-group, however, this paper innova-tively choose the bisphenol-A epoxy resin E44(DGEBA) as a crosslinking agent, the poly-ethylene-polyvinyl alcohol block copolymer (EVOH) which had excellent film-forming and inexpensive as experimental material, then used the polyphosphate acid (PPA) as the acidifi-cation of the phosphate reagent which could be connected to the matrix membrane in the form of covalent bond and would not be easily leached out. The performance of the membrane had been tested comprehensively. The preparation and characterization of the cross-linked EVOH/DGEBA membranes and the phosphorylated and cross-linked EVOH/DGEBA films had been investigated, and the application of the membranes for Fuel Cell had been discussed.EVOH was crosslinked using DGEBA as a novel crosslinker and DMAc as the solvent. The crosslinking reaction was confirmed by FT-IR, XRD and TGA, me-chanical performance and the oxidation stability. The properties of cross-linked EVOH/DGEBA membranes, including thermal stability, mechanical performance, oxidation stability, surface morphology were systematically investigated. The results showed that the membranes were thermally stable up to200℃. The oxidative stability of membranes was well improved after crosslinking. The remaining weight in the Fenton’s agent increased as the crosslinked degree’s raised. The SEM showed that the membrane’s surface was very smooth, and its structure was hollow.Using polyphosphate acid (PPA) as a phosphorylation agent, then prepared a series of different phosphorylation membranes by control the reaction time. The phosphorylated mem-branes were confirmed by FT-IR and Element analysis, and verified that the phosphate acid was connected to the matrix membrane in the form of covalent bond. The properties of phosphorylated and cross-linked EVOH/DGEBA membranes including thermal stability, oxidation stability, surface morphology, water uptake, dimensional stability, state of water and conductivity were systematically investigated. The results showed that the membranes had excellent thermal stability and oxidation stability, the degradation tempera-ture reached200℃. The phosphorylated membrane in Fenton’s reagent might be maintained at least until about200h, and then completely dissolved. The dimensional stability got worse with increasing temperature, and ion exchange capacity increased with the phosphorylation time increased. The low temperature DSC measured the content of the two state of water in-cluding the free water and the bond-water, with the treatment time of cross-linked DGEBA/EVOH film in the phosphoric acid increased, the content of both bond-water and free water increased; the phosphate-membrane’s conductivity at room temperature increased as the hu-midity increased.