改性聚偏氟乙烯接枝共混聚苯乙烯磺酸膜的制备与性能

Preparation and Performance of Modified Poly(vinylidene fluoride) Grafted onto a Blended Polystyrene Sulfonated Acid Membrane

将苯乙烯添加到溶有原硅酸钠改性的聚偏氟乙烯(PVDF)N-甲基吡咯烷酮溶液中,以过氧化苯甲酰(BPO)作引发剂,苯乙烯直接接枝到原硅酸钠改性的PVDF链上,成膜后磺化制备了聚偏氟乙烯接枝苯乙烯(PVDF-g-PSSA)膜.采用傅立叶变换红外光谱(FT-IR)、扫描电镜(SEM)、能量扩散X射线(EDX)和多功能材料实验机表征了膜的结构、形貌及硫和硅的分布、机械强度、溶胀度,使用阻抗分析和气相色谱仪研究了苯乙烯含量(w)对PVDF-g-PSSA膜的质子导电性能和阻醇性能的影响.结果表明,苯乙烯加入后,原硅酸钠改性的PVDF与苯乙烯进行接枝共聚反应,苯乙烯磺化反应不只是在膜表面进行,同时渗入到膜中进行,机械性能得到了改善.质子电导率(σ)随苯乙烯质量分数的提高而升高.Na4SiO4为8%和苯乙烯为20%的PVDF-g-PSSA膜,在25℃时溶胀度仅为20.4%,甲醇透过系数在10-7cm2·s-1数量级上,比Nafion115膜的低一个数量级.该膜具有较高的选择性,在直接甲醇燃料电池中具有良好的应用前景.

A proton exchange membrane of poly（vinylidene fluoride） （PVDF） grafted onto polystyrene sulfonated acid （PVDF-g-PSSA） was prepared as follows. Styrene was first added to N-methyl pyrrolidone （NMP） solution containing PVDF that was modified with plain sodium silicate. Benzoyl peroxide （BPO） was then added as an evocating agent and polystyrene was directly grafted onto the PVDF that was modified with plain sodium silicate. Lastly, the formed membrane was sulfonated. The microstructures, morphologies, and mechanical properties of the membranes and the distributions of sulfur and silicon were investigated using Fourier transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, energy dispersive X-ray （EDX）, and a multifunctional material experiment machine. The influence of styrene content on the proton conductivity and methanol permeability of these membranes was studied using an impedance analyzer and a gas chromatograph. Results showed that, depending on the content of styrene, styrene was easily grafted onto the PVDF that was modified by plain sodium silicate. A sulfonation reaction was also found to occur in the membranes and the mechanical properties had improved. As the styrene content increased, the proton conductivity of the PVDF-g-PSSA membranes also increased. The degree of PVDF-g-PSSA swelling was20.4% at 20% （w, mass fraction） styrene content and 8% Na4SiO4 and at 25℃. The membranes possess a methanol permeability of around 10-7 cm^2· s^-1, which is about ten times as few as that of Nafion115. These composite membranes have high selectivity and are promising for use in direct methanol fuel cells.