天然纤维粉体对PVDF/DMAc体系热力学及膜结构的影响

考察天然纤维粉体/聚偏氟乙烯(PVDF)/N,N-二甲基甲酰胺(DMAc)铸膜液热力学性质,采用浸没沉淀相转化法制备了天然纤维粉体/PVDF共混膜,表征了共混膜的结构和性质。结果表明,按照棉花粉体、羊毛粉体、无粉体的顺序,制膜体系越来越容易发生液固分相;并且棉花粉体/PVDF共混膜、羊毛粉体/PVDF共混膜、PVDF膜的孔隙率和水通量依次降低,结晶度依次增加,但膜形态一致,均为致密皮层和多孔亚层。共混膜性质的差异主要是由于纤维粉体亲水性的不同,添加亲水性较好的羊毛粉体的铸膜液成膜速度慢,而添加亲水性较低的棉花粉体的铸膜液成膜速度较快。

Influence of Natural Fiber Powder on Thermodynamics of PVDF/DMAcCasting Solution and Membrane Structure

The thermodynamics of polyvinylidene difluorid(PVDF)/ N-N-dimethylacetamide(DMAc) casting solutions with different natural fiber powders was investigated,and blend membranes of fiber powder and PVDF were prepared via immersion precipitation phase inversion.It is found that the membrane-for ming systems tend to induce the solid-liquid demixing as the following order of the system with cotton powder,with wool powder and without any powder.The porosity and water flux of cotton powder/PVDF blend membrane,wool powder/PVDF blend membrane and PVDF membrane decrease gradually,while the crystallinity of three membranes increases gradually.Three membranes exhibit the same morphology with the dense skin layer and porous sublayer.The property discrepancy of blend membranes is caused by the hydrophilicity of fiber powder.The precipitation rate of casting solution with better hydrophilic wool powder is slower than that of casting solution with poorer hydrophilic cotton powder.