Influence of Molecular Weight of Ultra-high Molecular Weight Polyacrylonitrile on Its Rheological Behavior in Dimethylsulfoxide

Ultra-high molecular weight polyacrylonitrile (UHMW-PAN ) was prepared by aqueous suspension polymerization, and the effect of molecular weight on its rheological behaviors hi dimethylsulf oxide (DMSO) and the spinning stability were investigated. It shows that, compared with common polyacrylonitrile ( C-PAN), UHMW-PAN/DMSO solution has smaller non-Newtonian index, larger structural viscosity index, much longer maximum relaxation time, and no first-Newtonian region appears in the flow curves under the same experimental conditions. The explanations for these phenomena are given in the view of chain-entanglements. The optimal technology of preparing UHMW-PAN fibers and hollow fiber membranes could be obtained based on the rheological study.     

EFFECT OF TEMPERATURE ON THE RHEOLOGICAL BEHAVIOR OF UHMW-PAN SOLUTION

UHMW-PAN is an important polymer material used to make high strength and high modules fiber as well as hollow fiber membrane with high mechanical strength to resist the backwash process.In this paper, the effect of temperature on non-Newtonian flow index, structural viscosity index,maximum relaxation time and zero shear viscosity of the UHMW-PAN solution has been studied.The relationship between parameters and spinnability has been discussed. On the basis of above works, the suitable temperature of spinning solution by gel-spinning has been found.     

纤维素-DMSO-PF浓溶液的粘弹性及其膜的研制和应用

把纤维素直接溶于二甲基亚砜(DMSO)和多聚甲醛(PF)中,能制成可纺性良好的纤维素浓溶液。测定其流变性能,首次直接得到纤维素浓溶液的粘流活化能等物理参数。以往这些物理参数都是间接地从纤维素酯、醚类的浓溶液获得,其准确性受酯、醚化条件的限制。我们研究了热力学和动力学条件与原液可纺性之间关系,获得最佳可纺性原液的热力学和动力学参数。在此基础上探讨了纤维素中空纤维膜的成形理论和成形工艺,首先用有机溶剂法纺制出纤维素中空纤维膜。调节原液条件和成形工艺参数,可在一定范围内调整中空纤维膜的透析能力。用溶剂法纤维素中空纤维膜组装成的人工肾透析器,具有良好的透析能力,能把血液中的低分子部分如尿素、肌肝等排出体外,而有用物质如B_(12)等则大部分保留,高分子部分如蛋白质、血球等则安全保留在血液中。经医院测定可在临床上进行应用。     

PAN基中空活性炭纤维的制备及性能研究

讨论了用聚丙烯腈（PAN）基中空纤维为原料，采用KOH活化法制备中空活性炭纤维（ACHF）的活化过程。考察不同KOH质量浓度对中空活性炭纤维性能的影响。测量了比表面积和得率，孔径分布，用碘吸附值、亚甲基兰吸附值测定了中空活性炭纤维的吸附性能，用SEM观察了其表面结构。结果显示，KOH活化法得到的中空活性炭纤维具有窄的孔径分布，较大的比表面积和较高的得率。     

Synthesis and Preparation of Polysulfone Hollow Fiber Chelating Membrane Modified with Thiourea

Several kinds of chloromethyl polysulfones （CMPF） with different chlorinity and reactive groups were synthesized by Friedel.crafts reaction, which could be utilized as reactively matrix membrane materials. The CMPF hollow matrix membranes were prepared with phase inversion by utilization of CMPF/additive/DMAC casting solution and CMPF as membrane materials. It was found that the effects of additive content, bore liquid and dry spinning distance on the structure of CMPF hollow fiber matrix membrane were different. A high qualified palysulfone hollow fiber chelating membrane modified with thiourea as chelating groups was prepared using CMPF as membrane matrix materials, through the reaction between thiourea and CMPF hollow fiber matrix membrane to afford the methyl iso-thiourium polysulfone. The experimental results showed that thermal drawing could increase the mechanical properties of matrix membrane, and the thermal treatment could increase the homogeneity and stability of the structure of polysulfoue hollow fiber chelating membrane modified with thiourea.     

A novel theoretical model for mass transfer of hollow fiber hemodialyzers

Hemodialyzers have been applied to hemodialysiswidely. In order to get accurate mass transfer coefficient and clearance to determine treatment time, their masstransfer models have been studied deeply. The domesticstudy on hemodialyzers is later, focuses on experiment, and seldom refers to theoretical mechanism[1,2], but theoverseas research is more in-depth. Simple one-dimensional models have been used to simulate mass transfer in hemodialyzers by many re-searchers[3—7]. Their models assumed …     

A novel theoretical model for mass transfer of hollow fiber hemodialyzers

A novel theoretical model for mass transfer of hollow fiber bundles in hemodialyzers is presented. In the model, a hemodialyzer is considered as a porous zone which is composed of two non-interpenetrating porous flow zones.Firstly, the dialysate side (shell side) is thought as a porous medium zone. Then by solidifying the dialysate flow zone and the occupied zone by hollow fiber membrane, the rest zone of bemodialyzer (i.e. blood side or lumen side) is considered as a porous medium zone too. Finally, the interface of the two flow zones is the fiber membrane through which mass transfer is performed. The dialysate and blood flows are all described by Navier-Stokes equations with Darcy momentum source terms. Kedem-Katchaisky equations as other source terms are added into Navier-Stokes equations to simulate the permeating flux through the membrane. All equations must be coupled together in the process of computing. The model is validated by the experimental data in literature. The simulative results show that the predicted clearances agree well with the experimental data, and the model in this paper is better than other models for the forecast of clearance.     

双膜分散法制备超细氧化锌颗粒

以氯化锌和氢氧化钠为反应物,中空纤维膜为分散介质,采用双膜分散法制备氧化锌颗粒。研究了两膜组件间距、分散相流速及表面活性剂对颗粒尺寸和形貌的影响。所得产物的SEM和粒度分布分析结果表明:两膜组件间距对颗粒平均尺寸无明显影响;无表面活性剂时,颗粒尺寸随着分散相流速的增大而增大,当流速从10 mL/min增大到40 mL/min时,平均粒径从307 nm增大到476 nm;表面活性剂的加入能有效抑制颗粒的生长,且颗粒尺寸随着分散相流速的增大而减小,当分散相流速由20 mL/min增至70 mL/min时,颗粒平均粒径由182 nm减小到45 nm。     

纺丝工艺对医用PAN中空纤维超滤膜性能的影响

采用干一湿法纺丝,制得性能良好的聚丙烯腈(PAN)中空纤维膜。分析了纺丝工艺对 PAN中空纤维超滤膜性能的影响。实验证明增加干纺程长度有利于改善 PAN 膜的的超滤性能。研究表明 PAN 中空纤维是一种具有多空基质的不对称膜,存在紧密的皮层,改变纺丝过程中的挤出速率、填充液压力、卷绕速率和拉伸倍数可以调节中空纤维的内外径和壁厚。     

静电纺丝法制备高分子纳米纤维的成因研究

对静电纺丝法制备高分子纳米纤维的成因进行了探究,主要通过分析高分子的结构与纺丝条件,寻找到静电纺丝法制备纳米纤维材料的一般规律。通过扫描电子显微镜(SEM)观察了高分子结构、分子量、溶液浓度和溶剂对高分子纳米纤维形貌的影响。实验结果表明:决定能否形成纤维的主要因素是高分子的结构和分子量,纤维的直径随着高分子溶液浓度的增加而增加,溶剂的挥发速率对纤维的形貌有决定性的影响。因此,利用静电纺丝法制备纳米纤维时应着重考虑以上四个因素的影响。     

Fabrication of a Polyamide/Polysulfone Hollow Fiber Composite Membrane

Introduction Appliedtomembraneseparationtechnology,components canbeseparatedmechanicallywhenasolutiongoesthrough asemipermeablemembrane.Themembranecanbesheet,spiralwound,tubeorhollowfiber,amongwhichhollow fiberisofthehighestspecificsurfaceandthusthemost effective.Thebestknownliquid phasemembraneprocessesare reverseosmosis(RO),ultrafiltration(UF),microfiltration(MF),dialysis,andelectrodialysis(ED).However,over thepastfewyears,anewmembraneprocesscalled nanofiltration(NF)hasemergedthatpromise…     

红细胞压积对血液透析器传质性能的影响

从理论和实验两方面研究了红细胞压（Ｈｃｔ）对ＳＴ１５中空纤维透析器尿素清除率的影响，结果表明，在临床范围内，Ｈｃｔ的变化（Ｈｃｔ＝０．２－０．４）仅影响血液测传质阻力和而对总传质阻力及溶质清降率影响较小，此外还讨论了提高中空纤维透析器溶质甭除率的可能窗径以及Ｈｃｔ对较大分子（肌酐，尿酸）清除率影响的特点及理论研究方法。     

Effect of Extractant and Cold-drawing on the Structure and Performance of HDPE Hollow Fiber Membranes Fabricated via Thermally Induced Phase Separation Method

IntroductionMicroporous membrane is widely used in filter ,oxygenator , contactor and battery separator . Traditionally ,polymer membranes shaped as porous hollow fibres , areprepared using the diffusion induced phase separationtechnique or DIPS[1].Inthis process ,a polymer solution ofa polymer and a solvent is contacted with a non-solvent forthe polymer . Because of initial interdiffusion of solventand nonsolvent ,the concentration in the polymer solutionchanges and, finally , phase separat…     

超滤洋葱伯克霍尔德菌CF-66发酵液提取抗菌物质的研究

对洋葱伯克霍尔德菌（Burkholderia cepacia）CF-66进行摇床培养,获得具有活性的抗菌物质。对其发酵液中抗菌物质的提取采用截留分子量为10 000的双酚A型聚砜中空纤维膜超滤。结果表明,在室温、膜两侧压差0.02～0.03 MPa、料液体积流量为14 L·h^-1时超滤,抗菌活性物质均截留在浓缩液中,超滤浓缩的体积比为2.0%～3.6%,清洗后的膜通量可恢复至97%以上。     

凝胶纺壳聚糖分散碳纳米管/聚丙烯腈纤维的研究

多壁碳纳米管(MWNTs)通过壳聚糖衍生物处理后与超高分子量聚丙烯腈进行复合,将得到的复合材料通过凝胶纺丝法制备出不同复合比例的MWNTs/聚丙烯腈纤维.将不同纺丝方法以及不同比例MWNTs对拉伸强度、模量、取向度、结晶结构的影响进行比较研究,同时通过电镜观察MWNTs的分散状况.结果表明:相比于湿法纺丝,通过凝胶纺丝法制备的复合纤维,MWNTs取向更好,分散更为均匀,纤维拉伸强度、模量都得到显著提高.对比未加MWNTs的对照样,在这个体系中加入质量分数为0.5%的MWNTs复合时,拉伸强度提高37%,弹性模量提高11.68%,并且声速取向度维持在相当高的水平(92.5%).     

腹水超滤中膜的污染及清洗

以人血清白蛋白溶液模拟腹水,采用聚砜中空纤维膜进行滤浓缩,实验考虑了不同截留相对分子质量膜的污染情况及膜清洗方法,并将优选出的实验条件用于腹水浓缩实验。结果表明,由于腹水中多种蛋白质的存在,造成膜的吸附污染较严重;用一般的化学清洗法清洗后通量可以恢复80％。     

后处理对聚丙烯中空纤维膜性能的影响

采用熔融挤出拉伸法制备了聚丙烯中空纤维膜，详细探讨了中空纤维的机械性能，尤其是各种条件对其弹性恢复性能的影响，研究发现后处理(热处理条件和牵伸比)对膜材料的孔隙率，平均孔径和气体的穿透性能有很大的影响，采用片晶和微纤模型可以很好地解释中空纤维膜的实验现象和成孔机理。     

中空纤维透析器管外传质系数的计算

假定中空纤维管空间排布服从正三角形和正方形排布,纤维管半径服从Gauss分布的前提下,从理论上推导出中空纤维透析器管外传质系数表达式,并分析管外液体流速、压降及流量恒定时纤维管半径的分散性对管外传质系数的影响. 结果表明,纤维管半径的分散性导致了中空纤维透析器传质系数的下降,且在高填充密度下,纤维管半径分散性的影响更加显著. 在相同的纤维管半径分散性下,正三角形排列方式要优于正方形的排列方式. 这对提高中空纤维透析器的透析效率以及对中空纤维透析器医疗器械的改进有重要意义.     

聚乙烯二甲基硅氧烷-聚偏氟乙烯复合分离膜的性能

为预测和评价聚偏氟乙烯(PVDF)和聚乙烯二甲基硅氧烷(PVDMS)多孔中空纤维复合膜的气体分离性能,提出了孔分布模型·通过比较模拟和实验结果,证明理论预测和实验结果具有很好的一致性·应用干 湿相转化法制备了PVDF多孔中空纤维膜,并且采用浸涂技术在PVDF中空纤维膜上制成厚度约为5～12μm的PVDMS致密膜层·通过气体渗透测试估计PVDF多孔基底膜的结构参数,同时也以氮气/氧气为介质对PVDMS PVDF复合中空纤维膜的分离性能进行了评价·实验结果表明,该复合膜具有较高的分离选择性,要制得致密无缺陷的复合膜,PVDMS致密涂层厚度不应小于5μm·     

Structure and Properties of Polyurethane/Polyvinylidene Difluoride Blending Hollow Fiber

IntroductionMembrane with the property of pressure-responsibili-ty ,PR,is one kind of membranes , and the pores of thismembrane can be changed reversibly with pressure in a se-paration system. This thus provides the membrane with agreat deal of advantages . For example ,the first is that thePR membranes can separate different masses by varyingpressures relating to its varying pore sizes ,and the secondis the regeneration of a fouled PR membrane easily becausethe pores could be enlargedin cle…