Synthesis And Characterization Of Side Chain Crosslinked Proton Exchange Membrane Materials

Methanol fuel cell is widely concerned with its characteristics of cleaning and high efficiency.Proton exchange membrane,one of the core components of proton exchange membrane fuel cell,has gradually become a hotspot in the field of proton exchange membrane fuel cell.Nowadays,the commercialized proton exchange membrane is Nafion membrane prepared by DuPont,but the high permeation of methanol and high cost have become the bottleneck of Nafion membrane development.Therefore,the preparation of novel proton exchange membrane materials to replace Nafion and other perfluorosulfonic acid films has become a hot topic.Poly(aryl ether nitrile has good mechanical strength,and high temperature resistance,corrosion resistance,easy preparation,low cost of production has been extensive research,containing sulfonic acid groups of sulfonated poly(aryl ether nitrile is expected to use as the next generation of proton exchange membrane.In this paper,the crosslinking modification of sulfonated polyaryl ether nitrile was carried out in order to obtain proton exchange membrane which has high stability,good methanol prevention and high conductivity.Specific research work is as follows:1.The sulfonated polyaryl ether nitrile was synthesized by nucleophilic substitution reaction with 2,6-difluorobenzene,phenolphthalein and potassium sulfonate as raw materials.A series of sulfonated polyaromatic ether nitrile with different sulfonic acid content were obtained by adjusting the ratio of phenolphthalein and potassium sulfonate.The cross-linked proton exchange membrane was prepared by covalent crosslinking.TGA analysis showed that CSPEN-X series crosslinking membrane has excellent thermal stability,nitrogen environment,weightlessness near 5%of the temperature at 300?.It can be seen from the data of water uptake and swelling that the dimensional stability of the cross-linked membranes is improved effectively.In the aspect of methanol prevention,the infiltration of methanol has been reduced by about twice.The conductivity of cspen-70 polymer film with 70%of sulfonic acid content was the highest with the ratio of methanol permeability,which was about five times as high as that of Nafion.2.In order to obtain a crosslinked proton exchange membrane which has good methanol prevention,PVA as crosslinking agent was selected.At the same time,considering the addition of polyvinyl alcohol,some sulfonate groups were lost,and the concentration of sulfonate was diluted.Before the experiment,polyvinyl alcohol was sulfonated to obtain the sulfonated polyvinyl alcohol.The obtained crosslinking membrane also has excellent thermal stability.In the case of methanol prevention,the lowest value of the SPEN-SPVA-40%sample was 8.08×10^-8 cm²?s^-1,which was significantly lower than Nafion 117.At the same time,this series of crosslinked membranes has good mechanical properties,the tensile strength is greater than 43 Mpa,and the young's modulus is greater than 1450 Mpa.In terms of the ratio of conductivity to methanol permeability,spen-spva-40%has the highest value,and its value is approximately 1.51×10⁵ S·S·cm^-3,and it has about 3.35 times of Nafion 117membrane.3.As a crosslinking agent,sulfonated polyvinyl alcohol has inhibited of methanol,but it also has a great influence on the proton conduction of the membrane.In order to reduce the influence of crosslinking on conductivity,potassium sulfonate was selected as crosslinking agent,and it was hoped to compensate for the loss of conductivity by increasing the content of sulfonate in unit mass.After crosslinking,the conductivity is less affected,and also has better performance in the methanol prevention.Therefore,this series of proton exchange membrane is more excellent in comprehensive performance selectivity.The ratio of electric conductivity of SPEN-SHQ-5%to methanol permeability is about 11.9 times that of Nafion 117,and has great potential as proton exchange membrane for proton exchange membrane fuel cell.