PTFE辐射接枝对苯乙烯基三甲氧基硅烷制备质子交换膜

A PROTON EXCHANGE MEMBRANE PREPARED BY RADIATION GRAFTING OF p-STYRYLTRIMETHOXYSILANE INTO PTFE MEMBRANE

采用聚四氟乙烯(PTFE)膜室温下共辐射接枝单体p-苯乙烯基三甲氧基硅烷(StSi),之后经磺化和水解缩聚制备了含有亲水性的—Si—O—Si—交联结构和Si—OH基团的质子交换膜.研究了溶剂、吸收剂量、吸收剂量率以及单体浓度等参数对接枝率的影响,并对质子交换膜的离子交换容量(IEC)、吸水性、尺寸稳定性及电导率等性能进行了分析.结果表明,实验条件下接枝率随吸收剂量和单体浓度增加而增加,采用<3mol·L-1的单体浓度减少均聚物;吸收剂量率为10～43Gy·min-1时,接枝率随剂量率变化不明显;以甲苯做溶剂可获得较高接枝率并保持膜的机械强度;IEC值、吸水性和电导率随接枝率增加而增大,是—SO3H、—Si—O—Si—交联结构和Si—OH基团共同作用的结果.接枝率72.5%时膜的IEC值为1.53mmol·g-1,高于Nafion117(0.89mmol·g-1),90℃吸水率为63%,尺寸稳定(优于Nafion117),质子电导率达1.5×10-2S·cm-1,获得了低于Nafion117的甲醇透过性,接枝率50.1%时甲醇透过系数0.82×10-6cm2·s-1.

A proton exchange membrane （ PEM） was produced by simultaneous radiation grafting of p- styryltrimethoxysilane （ StSi ） into polytetrafluoroethylene （ PTFE ） membranes,followed by sulfonation,hydrolyzation and condensation.The effects of solvent,absorbed dose,absorbed dose rate and monomer concentration on the degree of grafting （ DOG） were studied.Toluene was chosen for its higher boiling point and giving a higher DOG with acceptable mechanical strength.DOG increased with increasing the absorbed dose and monomer concentration and changed little with the absorbed dose rate at 10 ～ 43 Gy·min -1.Monomer concentration of 3 mol·L -1 was better for reducing the copolymer.The degree of sulfonation （DOS） was as high as 92% ～ 97% at DOG 23% ,making the properties of the PEM rely much on the DOG.Scanning electron microscopy （SEM） gave imagines of radiation grafting happened through the surface to the centre of the membrane.The ion exchange capacity（ IEC）,water uptake,dimension expansion and proton conductivity grew up with the increase of DOG for more hydrophilic —SO3H,—Si—O—Si— crosslinking structure,and Si—OH groups were incorporated in the PEM.In addition,proton conductivity got better with temperature increase due to the good water uptake.Most of the grafted membranes exhibited lower methanol permeability than Nafion .The prepared PEM in this work showed a good combination of high IEC （1.53 mmol·g -1 ）,dimension stability （dimension changed less than Nafion 117 at 90℃ ）,acceptable water uptake （ 63% at 90℃ ） and proton conductivity （ 1.5 × 10 -2 S·cm -1 at 90℃ and DOG 72.5% ）,and low methanol permeability （0.82 × 10 -6cm2·s -1 at DOG 50.1% ）.