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溶剂对PVDF铸膜液相转化和微孔膜皮－亚两层结构的不同影响

期刊名称：高分子学报， (6).522-528, 2008，
时间：0
分类：TQ028.8[化学工程] TP393[自动化与计算机技术—计算机应用技术;自动化与计算机技术—计算机科学与技术]
作者机构：[1]武汉科技学院新型纺织材料绿色加工及其功能化教育部重点实验室,武汉430073, [2]浙江大学高分子科学研究所,杭州310027
相关基金：国家自然科学基金（基金号50433010）重点资助项目和武汉科技学院青年基金（基金号20063124）资助项目.
相关项目：聚合物纤维和薄膜制备中多层次结构控制的研究

关键词： PVDF非对称膜, 皮-亚分步凝固, 相分离, 动力学传质, 分相时间, PVDF asymmetrical membrane, Skin-sublayer two step precipitation, Phase separation, Kinetic mass transfer, Demixing time

中文摘要：

采用皮-亚分步凝固成膜机理分析了3种不同溶剂对聚偏氟乙烯（PVDF）铸膜液相转化和膜结构的影响,采用浊度法测定铸膜液体系的热力学性质,沉淀速度采用光透射仪测定.结果显示,3种膜的皮层分相主要由热力学性质控制,均发生延时液固分相,生成了相互融合的球粒组成的致密皮层.3体系的亚层分相行为由动力学扩散过程控制;对于二甲基亚砜（DMSO）、N,N-二甲基乙酰胺（DMAc）体系亚层发生瞬时液液分相,结晶化对动力学过程影响小,表现为光透射曲线上分相时间t2短,生成了大孔结构为主的亚层,膜厚度、孔隙率和气通量均高、结晶度低;N,N-二甲基甲酰胺（DMF）体系亚层发生延时液液分相,结晶化对动力学过程影响大,t2长,生成蜂窝状孔结构亚层,其膜厚度、孔隙率和气通量较低,但膜的结晶度高.

英文摘要：

Poly（vinyldiene fluoride）（PVDF） asymmetrical membranes using three solvents N,N-dimethylforamide（DMF）,N,N-dimethylacetamide（DMAc）, and dimethylsulfoxide（DMSO） were prepared by phase inversion process.The thermodynamic properties of the casting solutions and the kinetic diffusion during membrane-forming processes were investigated via cloud point determination and light transmittance measurements.It was found that the thermodynamic stability of the casting solutions was enhanced gradually from DMSO/PVDF/water,DMF/PVDF/water to DMAc/PVDF/water,the delayed demixing due to the decrease of kinetic diffusion rates was easier to occur as the solvents were changed from DMF,DMAc to DMSO.The characterization of membranes showed that membranes containing a macrovoid structure were fabricated with higher porosity and lower crystallinity when DMSO and DMAc were used as solvent,but the honeycomb-structure membranes with higher crystallinity and lower porosity were prepared from DMF solvent,which indicated that the three membranes morphologies and properties were not controlled by the thermodynamic property or kinetic process uniformly.As a result,based on the theory of ＂the predominance on the growth of preformed nucleus＂ and the macrovoid development,the influences of the three solvents on the phase separation behavior of PVDF casting solutions,PVDF aggregate structure and membrane structure were discussed by the membrane formation mechanism of skin-sublayer two step precipitation.The results showed that for the three membrane-forming systems using DMF,DMAc and DMSO as solvent respectively,the delayed solid-liquid demixing took place in the skin layer under the control of the thermodynamics of casting solutions,and the dense skin layer formed with spherical particles.The delayed time was controlled by the kinetic diffusion.Mutual diffusion coefficient of solvent and non-solvent （Dm） increased gradually in the order of DMSO,DMAc,DMF,therefore,the delayed time decreased following the sequence of DMS