聚全氟乙丙烯中空纤维膜研究

以聚全氟乙丙烯(FEP)为成膜聚合物,复合无机粒子为成孔剂,邻苯二甲酸二辛酯(DOP)为稀释剂,采用熔融纺丝工艺制备得到FEP中空纤维膜.分析和讨论了不同成膜体系对FEP中空纤维膜热性能、动态力学性能和力学性能的影响,并对膜的纯水通量和孔径分布进行表征.用扫描电子显微镜(SEM)观察了膜的横断面和表面形貌.结果表明,所得FEP中空纤维膜为由溶出微孔和界面微孔组成的海绵状孔结构.随着成孔剂含量的增加,成孔剂在成膜体系中分散程度变差,容易发生团聚,最终导致膜孔径变大,孔径分布变宽.成孔剂和稀释剂对FEP中空纤维膜的热性能和动态力学性能影响较小.当FEP含量增加到70 wt％时,膜表面容易形成一层致密层,降低了膜的通透性.     

熔融纺丝-拉伸法制备PVDF中空纤维膜及其油-水分离性能

以聚偏氟乙烯(PVDF)为成膜聚合物, 聚全氟乙丙烯(FEP)为添加剂, 聚乙二醇(PEG)和氯化钙(CaCl₂)为复合成孔剂, 采用熔融纺丝-拉伸法制备了PVDF中空纤维膜. 在制膜过程中未使用其它溶剂和稀释剂, 实现了制膜过程的相对绿色化. 分析和讨论了拉伸比对PVDF中空纤维膜结构与性能的影响, 测试了纤维膜的孔径分布、 力学性能和油-水分离性能等. 结果表明, 进行拉伸后处理的膜的孔径分布较窄, 在油包水乳液分离测试中, 分离效率均在97%以上, 表现出良好的油-水分离效果.     

界面预湿处理对异质增强型PVDF中空纤维膜结构与性能的影响

以熔融纺丝聚氯乙烯(PVC)中空纤维多孔膜为增强体,聚偏氟乙烯(PVDF)为成膜聚合物,聚乙烯吡咯烷酮(PVP)为添加剂,N,N-二甲基乙酰胺(DMAc)为溶剂,配置铸膜液,采用同心圆牵引-涂覆法制备了异质增强型PVDF中空纤维膜.制备过程中,采用预湿溶液对增强体基膜表面进行预处理,研究了预湿溶液组成及含量对异质增强型PVDF中空纤维膜结构与性能的影响.结果表明,未经预湿处理的异质增强型PVDF中空纤维膜具有较厚的致密界面层;预湿溶液可对基膜表面孔起到保护作用,使异质增强型PVDF中空纤维膜的界面层变薄或形成多孔界面层,有益于改善增强型PVDF中空纤维膜的通透性能;与二甲基乙酰胺(DMAc)水溶液相比,以乙醇水溶液为预湿溶液所得异质增强型PVDF中空纤维膜的性能较优;当预湿液中乙醇含量为60 wt%时,所得增强型PVDF中空纤维膜的渗透性能较优,拉伸强度可达8.61 MPa.     

熔融-拉伸法制备亲水聚丙烯/聚乙烯醇缩丁醛中空纤维膜

以聚丙烯(PP)为基材,聚乙烯醇缩丁醛(PVB)为亲水改性剂,聚丙烯接枝马来酸酐(PP-g-MAH)为增容剂,通过熔融-拉伸法(MS-S)制备亲水PP/PVB中空纤维膜.采用差示扫描量热(DSC)和水接触角(WCA)测试考察了PVB添加量对PP/PVB共混物结晶行为及亲水性的影响;采用广角X射线衍射(WAXD)和小角X射线散射(SAXS)研究了PP/PVB中空纤维热处理后片晶微观结构;采用场发射扫描电镜(FESEM)观察了PP/PVB中空纤维膜内表面孔结构的变化,测试了PP/PVB中空纤维膜的孔隙率及纯水通量.研究结果表明,随着PVB含量的增加,PP/PVB共混物的WCA从103°降低到76°,表明PP/PVB共混物亲水性得到明显改善.同时,PVB可以起到异相成核作用,但由于MAH与PVB发生键合作用,过量添加PVB会阻碍PP分子链段运动,导致晶体结构不完善,这与WAXD和SAXS分析结果相同.PP/PVB2.5(PVB质量分数为2.5%)中空纤维膜热处理后结晶度、片晶取向度、厚度及Shish-kebab结构完善度均高于纯PP样品.对应膜孔隙率为66%,纯水通量达到320 L/(m2·h),比纯PP膜提高了76.8%.     

扫描电镜用于PTFE拉伸微孔膜的形态结构研究--研制中PTFE拉伸微孔膜的SEM鉴定

运用扫描电镜(SEM)图像研究了聚四氟乙烯(PTFE)粉料经过推挤、辊压和拉伸得到的微孔膜的形态结构,观察到膜是由网状纤维及由它所连接的结点所组成.单相和双向拉伸显著影响到膜结构的改变,而未经热处理的拉伸膜的丝状纤维在放置中收缩改变了膜的微孔形态结构,但在孔径测定中没有显著变化.认为纤维丝是PTFE粉料在推挤和辊压中形成的结点在拉伸中伸展引出的并产生孔隙,而由于从SEM仅能观察到1 nm深度的膜表面层,厚度达数十微米多孔膜的孔径分布应是很错杂的.     

无机粒子杂化FEP微孔膜结构与性能研究

以聚全氟乙丙烯(FEP)为成膜聚合物,复合无机粒子(由微纳米级Si O2、Na Cl及界面处理剂等构成)为成孔剂,邻苯二甲酸二辛酯(DOP)为增塑剂,用热压法制得了具有界面孔结构特征的均质FEP/无机粒子杂化平板膜.研究了复合无机粒子含量对FEP平板膜结构与性能的影响,并对其渗透性能,截留率,孔隙率及机械性能进行测试表征.结果表明,FEP杂化膜表层无机粒子分布较少,大部分都被基质相包裹.由于FEP的低表面能,FEP易与无机粒子发生界面相分离,水溶性无机粒子经溶解后形成微孔结构.随无机粒子含量增加,膜孔数量增加,孔隙率和渗透性能明显提高,而碳素墨水截留率有所降低,力学性能呈先增大后减小的趋势.     

TiO_2/PVDF复合中空纤维膜的制备和表征

采用相转化法制备了二氧化钛 (TiO2 ) 聚偏氟乙烯 (PVDF)复合中空纤维膜 .应用牛血清白蛋白截留实验、扫描电子显微镜、热重分析、X射线衍射分别对复合膜的分离性能、微观结构、热稳定性和晶相组成进行了分析 .结果表明复合膜的性能与纯PVDF膜的相比有显著的改善 ,其中对牛血清白蛋白的截留率从 3 2 7%提高到 86 6 7% ,单根纤维的断裂应力从 3 35MPa提高到 4 70MPa ,提高了 4 0 3% .氮气吸附实验测定的孔径分布进一步表明复合膜的孔径分布变窄 ,孔径变小 .     

增强复合静电纺纳米纤维膜

静电纺丝纳米纤维膜具有孔隙率高、孔径小、透气性好等优良性能。但由于纤维太细,且纤维间没有有效的粘结,其强度较低,严重限制了它的应用。本文采用高/低熔点热熔性的两种高聚物进行混合静电纺丝,制备了聚丙烯腈/聚偏氟乙烯-六氟丙烯(PAN/PVDF-HFP)、聚偏氟乙烯/聚偏氟乙烯-六氟丙烯(PVDF/PVDF-HFP)复合纳米纤维膜,并通过110℃、3MPa、5min的热压后处理,使PVDF-HFP部分熔融,制得具有点粘结的增强复合纳米纤维膜。测试结果显示,较处理前,增强PAN/PVDF-HFP、PVDF/PVDF-HFP复合纳米纤维膜的拉伸断裂强度分别提高了923.1%和665.7%,达到17.8MPa和26.9MPa,且同时保留了优良的孔隙率与透气性能。     

纤维编织管增强型中空纤维膜研究

采用二维编织技术将聚丙烯腈(PAN)长丝编织成中空纤维编织管作为增强体,分别以聚丙烯腈(PAN)和聚偏氟乙烯(PVDF)为成膜聚合物,N,N-二甲基乙酰胺(DMAc)为溶剂,聚乙烯吡咯烷酮(PVP)为添加剂,调制铸膜液,采用同心圆挤出-涂覆法制备了PAN纤维编织管同质增强型PAN中空纤维膜和异质增强型PVDF中空纤维膜.研究表明,所得PAN纤维编织管增强型中空纤维膜断裂强度最大可超过75 MPa,在伸长率10%范围内,表面分离层与增强体之间界面结合良好;表面分离层具有类似于非对称膜的结构,铸膜液可浸入纤维编织管纤维空隙中,铸膜液浸入部分固化后未影响膜的通透性能;随成膜聚合物浓度增加,膜纯水通量减小,牛血清白蛋白(BSA)截留率增大;随添加剂PVP浓度增加,膜的纯水通量先增大后减小,在8 wt%左右达最大值,BSA截留率随PVP浓度增加而单调增加;同质增强型中空纤维膜界面结合程度优于异质增强型.     

电活性聚乳酸纳纤膜的形态调控及高效捕集PM0.3性能

通过静电喷雾沸石咪唑框架-8(ZIF-8)分散液对同步电纺聚乳酸(PLA)纳米纤维进行表面功能化,以增强PLA/ZIF-8纳米纤维膜(简称纳纤膜)表面的电荷俘获及储存能力,从而提高静电吸附效果和过滤性能.通过在分散液中添加不同量的ZIF-8来调控锚定于纤维表面的ZIF-8负载量,探究ZIF-8含量与纤维膜形态和性能演变之间关系.采用扫描电子显微镜(SEM)对纤维膜的微观形态进行表征,并结合傅里叶变换红外光谱(FTIR)和X射线衍射谱(XRD)分析了纤维膜的化学性质、界面相互作用和晶体结构的演变机理.采用静电测试仪、电介质测试仪和静电计分别评价表面电势、相对介电常数和输出电压,表征纤维膜的电活性和摩擦电输出性能.通过万能试验机测试聚乳酸纳米纤维膜的力学性能,并使用自主搭建的空气过滤测试平台探究纤维膜高效过滤机理.结果表明,PLA/ZIF-8纳纤膜具有高电活性、高过滤效率、低空气阻力和优异的力学性能:其表面电势和最大开路输出电压分别可达5.9 kV和30.9 V,与纯PLA对比样相比分别提升5.6倍和5.3倍,同时拉伸强度和拉伸韧性增幅分别高达78%和111%.更重要的是,PLA/ZIF-...     

Structure and microporous formation of cellulose/silk fibroin blend membranes: Part II. Effect of post-treatment by alkali

Blend membranes (RCF1) were prepared from mixture solution of cellulose and silk fibroin (SF) in cuoxam by coagulating with acetone–acetic acid (4:1 by volume). The blend membranes were subjected to post-treatment with 10% NaOH aqueous solution, and their structure and properties were characterized by FT-IR, X-ray diffraction, DSC, SEM and DMTA. In previous work, cellulose/SF blend membranes (RCF2) prepared by coagulating with 10% NaOH aqueous solution formed a microporous structure, in which the SF as a pore former was almost completely removed from the membrane. However, when the blend membranes RCF1 were immersed in 10% NaOH aqueous solution for post-treatment, a strong hydrogen bonding between cellulose and SF inhibited the removal of SF. Although alkali is a good solvent for SF, the blend membranes RCF1 such obtained from cellulose and SF were alkali resistant. The crystallinity and the mean pore size of the blend membranes slightly decreased with increasing post-treatment time. This work provided a cellulose/silk blend membrane, which can be used under alkaline medium.     

泡压-滤速法研究聚丙烯微孔膜的孔径及其分布

膜科学与膜技术作为新兴的材料科学分支之一,在国民经济中发挥着越来越重要的作用．近年来,高分子微孔膜的研究与应用正引起人们日益增长的关注．采用双轴拉伸方法制备的聚丙烯微孔膜同时具备了良好的力学性能和透过性能［１］,克服了单轴拉伸方法各向异性的缺点,是一...     

A novel polypropylene microporous film

The structure and properties of a polypropylene microporous film prepared by biaxial stretching of non-porous polypropylene film of high β-crystal content were investigated. The porosity of these films can be as high as 30–40%, and the average pore size was around 0.05 μm. The films were found to have the structure of a two-phase interpenetrating network; both the polypropylene and the pore regions were three-dimensionally continuous. The advantages of the biaxially stretched microporous films are the combination of high permeability to fluids with good mechanical properties and almost circular pore shape with narrow pore size distribution. The application of this microporous film for battery separators, filtration membranes and substrates of functional polymer composites is discussed.     

MICROPOROUS INORGANIC MEMBRANES

Recent development in microporous inorganic membranes represents a significant advance in materials for separation and chemical reaction applications. This paper provides an in-depth review of synthesis and properties of two groups (amorphous and crystalline) of microporous inorganic membranes. Amorphous microporous silica membranes can be prepared by the sol-gel and phase separation methods. Flat sheet, tubular and hollow fiber amorphous carbon membranes have been fabricated by various pyrolysis methods from polymer precursors. A large number of synthesis methods have been developed to prepare good quality polycrystalline zeolite membranes. Several techniques, including vapor and liquid approaches, are reviewed for pore structure modification to prepare microporous inorganic membranes from mesoporous inorganic membranes. Chemical, microstructural and permeation properties of these microporous membranes are summarized and compared among the several microporous membranes discussed in this paper. Theory for gas permeation through microporous membranes is also reviewed, with emphasis on comparison of theoretical with the experimental data. These inorganic microporous membranes offer excellent separation properties by the mechanisms of preferential adsorption, selective configurational diffusion or molecular sieving.     

PREPARATION AND CHARACTERIZATION OF PVDF-HFP MICROPOROUS MEMBRANE BY TEMPLATE METHOD

Porous poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF-HFP） membranes were successfully prepared using dibutyl phthalate （DBP）, polyvinylpyrrolidone （PVP-K30）, polyethylene glycol 200 （PEG200） as templates. SEM was used to examine the morphology of the PVDF-HFP porous membranes. It was found that these membranes have an asymmetric structure and the blends of PVDF-HFP/DBP formed nanoporous membranes, whereas the blends of PVDF- HFP/PVP-K30 formed ＂sponge-like＂ and microporous membranes. Moreover, the average pore size and porosity was about 0.3 μm and 48.7%, respectively. The crystallinity, thermal stability and mechanical strength of membranes were characterized by XRD, DSC, TGA and stress-strain tests. The results showed that the membranes are a crystals with excellent thermal stability. It was an effective way to regulate pore size and morphology of the PVDF-HFP membranes.     

微孔型聚丙烯腈固体电解质的结构与导电性能研究

用蒸汽相沉析法和液相沉析法分别制备了两类高孔隙率的聚丙烯腈 (PAN)微孔膜 .用扫描电子显微镜对微孔膜的形态进行了观察 ,发现前者为均匀的蜂窝状结构 ,而后者则具有不对称的三层次结构 .又用这两类微孔膜分别制备了两个系列的微孔型PAN电解质 .电性能测试表明前者的室温电导率较高 ,可以达到 4×10 - 3 S cm ,后者的电导率则相对较低 .微孔膜本身诸因素对微孔型PAN电解质电导率的影响顺序为微孔膜结构—孔隙率—微孔孔径     

Is condensation the cause of plasma leakage in microporous hollow fiber membrane oxygenators

Extracorporeal membrane oxygenators are comprised of large bundles of microporous hollow fiber membranes (HFMs) across which oxygen and carbon dioxide are transferred to and from blood. Long term use of extracorporeal oxygenators is limited by plasma leakage through the pores of the HFM walls, requiring replacement of the oxygenator. Condensation of water vapor on the pore walls is thought to be a possible precursor to plasma leakage. To explore this mechanism, a simple theoretical analysis is used to examine the temperature of the gas flow through the HFMs. For conditions representative of two commercially available oxygenators, the analysis predicts that the gas heats up to the temperature of blood flow outside of the fibers after passing through less than 0.5% of the fiber lengths. Once the gas temperature and hence the fiber wall temperature equilibrates with the blood, condensation of water vapor is no longer possible. In vitro testing of microporous HFMs under gas flow rates and temperature conditions similar to those of extracorporeal oxygenators but with the fibers submerged in water is also presented. The fibers showed negligible degradation in carbon dioxide transfer over a four-day period. These results of both the theoretical and experimental analyses indicate that the condensation of water vapor within the pores of the HFMs is unlikely to be the cause of plasma leakage in clinically used extracorporeal oxygenators.     

Preparation of microporous membranes by paste method

Microporous membranes were prepared by the paste method. Certain properties of the resultant microporous membranes such as porosity, pore size, specific surface area, and N₂ gas permeability were estimated. Furthermore, the membrane structure was observed with the aid of scanning electron microscopy. It was elucidated that the membranes consist of aggregates of minute spherical particles, made up of poly(styrene-divinylbenzene) with micropores.     

纳米Fe3O4/PVDF磁性复合膜的原位制备及表征

通过膜相渗透原位化学沉积法制备了聚合物基Fe3O4/聚偏氟乙烯（PVDF）磁性纳米复合膜，研究了复合膜制备的适宜条件，采用红外光谱（FT-IR）、差热分析（DSC）、X射线衍射、扫描电镜（SEM）等手段对复合膜的组成、结构进行了表征和分析，通过气体渗透法测定了复合膜的孔径随制备条件的变化情况. FT-IR和XRD图谱结果表明，在基膜中原位生成Fe3O4后不影响基膜PVDF的分子结构；复合膜中的Fe3O4粒子尺寸为68 nm左右，复合膜的磁化率达0.044 cm3•g－1；复合膜的磁化率、平均孔径、最大孔径及孔径分布范围随反应条件的改变而有明显变化.