聚酰亚胺中空纤维气体分离膜的物理老化现象

The Physical Aging Phenomenon of Polyimide Hollow Fiber Membranes for Gas Separation

以聚酰亚胺6FDA-mPDA为原料制备了单层非对称中空纤维膜,以聚酰亚胺Matrimid5218为分离层材料制备了双层非对称中空纤维膜,膜的致密层厚度为0.09-0.21μm。测试了中空纤维膜的O2、N2、CH4和CO2等气体渗透性能随时间的变化,研究了中空纤维膜物理老化现象。结果表明,随着老化的进行,气体渗透速率逐渐减小,分离系数逐渐变大,直至平衡。以自由体积扩散机理为基础,针对非对称中空纤维膜具有超薄皮层的特点,建立描述物理老化过程的数学模型。结果表明,该模型与实验结果相吻合,表明自由体积扩散机理可用来描述具有超薄皮层的中空纤维膜的物理老化现象。

The single-layer asymmetric hollow fiber membranes made from polyimide-6FDA-mPDA and the dual-layer asymmetric hollow fiber membranes with the selectivity layer made from polyimide-Matrimid⑧ 5218 were prepared with the thickness range of 0.09~0.21 μm. The physical aging phenomenon of the prepared asymmetric hollow fiber membranes was studied, and the gas permeability varying with time for gases of O2, N2, CH4 and CO2 were tested. Experimental results show that, during physical aging, the gas permeance decrease and the selectivities increase, while finally both come to a state of equilibrium. According to the characteristic of ultra-thin dense skins, a mathematical model based on the free volume diffusion mechanism was developed to describe the physical aging of the hollow fiber membranes. The results show that, according to the model developed, the results calculated agree well with the experimental results. It indicates that the free volume diffusion mechanism can be used to describe the physical aging phenomenon of the hollow fiber membranes with ultra-thin dense skins.