单轴拉伸对Nafion 结构及性能的影响

²H NMR 和PFG-NMR 用于研究拉伸过程中Nafion 结构的改变以及对溶剂分子运动性质的影响．²H 谱表明单轴拉伸Nafion 膜在拉伸比率较低情况下（L < 5）,通道排列取向程度随着拉伸比率变大而增大,同时扩散实验表明水分子的运动能力也得到增强,表明取向化的通道网络有助于增强材料取向方向质子的导电能力,可以用于提高质子膜材料性能．在取向达到最大值后（L≥5）继续拉伸,膜内水分子的移动能力相比略有降低．溶胀实验表明取向膜的溶胀行为呈各向异性,拉伸作用致使膜内通道沿拉伸方向取向排列,通道的取向效应使得其在垂直拉伸方向（Y）和膜厚度方向（Z）溶胀更为显著．拉伸Nafion 膜对甲醇的吸附能力随着拉伸比率的增加而增强,同时甲醇的扩散数据显示,甲醇的运动能力在该通道网络中也随着拉伸比率的变大而不断增强,甲醇燃料在该类质子膜内的渗透效
应得以增强,不利于其在直接甲醇燃料电池中的应用．

Effects of Stretching on Nafion Morphology and Properties

²H NMR and PFG NMR were performed on uniaxially stretched Nafion membrane to evaluate the deformation effects on its morphology and properties. We
conducted a systematic study on Nafion over draw ratio range from 1 to 7. Uniaxial deformation was found to lead a strong alignment of the hydrophilic channel, and enhance the water mobility along the draw direction before reaching the max orientation (L<5). These effects could be used for improving the PEMs´ properties. The deformation after the max orientation (L≥5) led to a decrease of mobility of the water molecules. This stretching effect also led to anisotropic swelling of the membranes in solvent as the channels align along the draw direction. The absorption and mobility of methanol increased as the draw ratio, hindering its application in DMFC.