低温热致相分离法制备聚偏氟乙烯中空纤维多孔膜的研究

提出了一种低温热致相分离成膜方法(L- TIPS),通过干-湿法纺丝工艺制备了聚偏氟乙烯( PVDF)中空纤维多孔膜,考察了非溶剂致相分离法(NIPS)和热致相分离法(TIPS)两种成膜机理的竞争关系对膜形态结构和性能的影响.结果表明:低温热致相分离法在制备PVDF中空纤维膜的过程中同时发生了非溶剂致相分离机理和热致相分离机理,与单纯非溶剂致相分离机理成膜相比,膜断面未出现大的空穴,仅有少量指状孔,中部为球状结构,内外表面均有皮层,增强了膜的抗污染性能和强度;铸膜液浊点温度与凝固浴温差越大,壁厚越厚,热致相分离作用越明显,非溶剂致相分离作用相对减弱,膜的纯水通量和强度均有所提高,卵清蛋白截留率变化不大;低温热致相分离法比传统热致相分离法制膜温度低,能够添加常用的亲水性高分子添加剂(PVP、PEG、PVA).     

P84共聚聚酰亚胺湿法纺丝溶剂的选择

P84共聚聚酰亚胺能溶于常见的非质子溶剂进行湿法纺丝。良溶剂可以制得性能稳定的纺丝浆液,这对得到结构相对密实的聚酰亚胺纤维很重要。本文从聚合物和溶剂溶度参数的计算,P84共聚聚酰亚胺在不同溶剂中的特性黏度测试以及P84共聚聚酰亚胺/溶剂/水三元体系的相图三方面出发,比较分析了较适合P84共聚聚酰亚胺湿法纺丝的溶剂。结果表明,P84的溶度参数为10.35,与N-甲基吡咯烷酮(NMP)和N,N′-二甲基乙酰胺(DMAc)的溶度参数(分别为11.23和11.14)较接近;P84-NMP,P84-DMAc和P84-DMF的特性黏度分别是0.807,0.657和0.615;结合相图得到NMP、DMAc以及N,N′-二甲基甲酰胺(DMF)比较适合P84湿法纺丝,其中NMP最佳。     

聚合物PPES／PPEK／PPESK—NMP—H2O三元体系的相行为研究（Ⅱ）相图的计算

以Flory-HugginS理论为基础,详细推导了聚合物-溶荆-非溶剂三元聚合物成膜体系的双节线、旋节线和临界点求解方程,提供了方程的求解方法.根据此理论和方法,分别求解了聚合物杂萘联苯聚芳醚砜酮、杂萘联苯聚芳醚砜和杂萘联苯聚芳醚酮与H2O及NMP组成的三元体系在25℃时的相分离曲线.将计算结果与实验测定的浊点数据进行比较.分别优化校正了溶剂NMP与聚合物PPES、PPEK和PPESK之间的相互作用参数g23.提出二元Flory-HugginS相互作用参数值随温度变化的一般关系.并据此关系,以25℃时的相互作用参数为基准求解PPES/PPEK/PPESK-NMP-H2O三元体系在50℃和75℃时的相图,计算结果与浊点实验数据相吻合.     

非溶剂对成膜过程凝胶速率的影响

基于Flory-Huggins高分子溶液理论,计算了聚砜(PSF)-二甲基乙酰胺(DMAc)-非溶剂铸膜体系的三元相图,其中二甲基乙酰胺(DMAc)为溶剂,水、甘油、乙醇和正已烷为非溶剂．通过相图分析了不同非溶剂对凝胶时间的影响,同时考虑了扩散的影响．根据计算结果得到如下结论:双节线或旋节线与聚合物-溶剂轴的距离越近,凝胶时间越短;非溶剂与溶剂的相互扩散速度越快,凝胶时间越短;联结线的斜率越小,即分相时聚合物稀相中非溶剂的量越少,凝胶时间越短。     

PAN湿法纺丝中凝固成纤过程的研究进展

综述了PAN湿法纺丝中的凝固成纤过程的研究进展,主要介绍了成纤过程中溶剂与沉淀剂的双扩散的理论研究情况,讨论了凝固浴条件包括凝固浴温度、浓度及纺丝原液的固含量对双扩散及纤维结构与性能的影响,对PAN原丝及其碳纤维的发展与应用作了简单介绍.     

复合热致相分离制膜方法

系统介绍了北京坎普尔环保技术有限公司自主创新研发成功的复合热致相分离(complex Thermally Induced Phase Separation,简称为c-TIPS)制膜方法,并与经典的热致相分离(TIPS)制膜方法和修正热致相分离(m-TIPS)制膜方法作了比较.c-TIPS法以水溶性良溶剂和水溶性添加剂组成的混合物作为"复合稀释剂",在加热搅拌罐中,于聚合物熔点(Tm)以下的温度(一般为90～170℃)下形成聚合物/复合稀释剂体系的均相溶液,在相同温度或低5～10℃的温度下纺丝,通过控制芯液和冷却液的组成,利用同时或先后发生的热致相分离(TIPS)和非溶剂致相分离(NIPS)过程的复合相分离过程,制备了强度高、通量大、外表面有皮层(超滤膜)和没有皮层(微滤膜)的新型中空纤维(毛细管)多孔膜.该方法适用于几乎所有半结晶性和非结晶性制膜材料,例如,PVDF,PES,PS,PVC,PAN,PMMA,CA,等,所得膜的综合性能大大优于用NIPS法制备的同样材料的膜性能.     

热致相分离法制备乙烯三氟氯乙烯共聚物微孔膜——混合溶剂的选择

研究了混合溶剂对热致相分离法制备乙烯三氟氯乙烯共聚物(ECTFE)微孔膜的影响,考察了不同非溶剂对ECTFE/癸二酸二丁酯(DBS)体系结晶趋势的影响.通过相容性分析及ECTFE微孔膜断面结构的观察,非溶剂亚磷酸三苯酯(TPP)的加入能使ECTFE/DBS体系从固液相分离转变为液液相分离.当非溶剂与溶剂的质量比比例(TPP∶DBS)为4∶6时,可制得孔径均匀的双连续结构ECTFE微孔膜.此比例下的热力学相图显示,ECTFE/DBS/TPP三组分体系具有较宽的液液相分离区,该体系偏晶点所对应的ECTFE质量分数高达50%.     

湿法纺丝条件对临界凝固时间的影响

以聚丙烯腈-二甲基亚砜-水体系为研究对象,通过建立数学模型,对聚丙烯腈湿法纺丝凝固的初期阶段进行研究。借助MATLAB软件,采用有限元法对数学模型进行求解。利用数学模型考察纺丝条件对纺丝液临界凝固时间的影响。结果表明:(1)凝固浴浓度在一定程度上决定凝固进程;纺丝液临界凝固时间随凝固浴浓度升高而增加,且增加的趋势是越来越快,当浓度大于60%尤为明显;(2)纺丝液临界凝固时间随纺丝液中水含量的增加而减小,使纺丝液凝固时发生瞬时相分离的趋势增大;(3)随着喷丝孔直径的增加,纺丝液临界凝固时间会延长。     

稀释剂种类对聚偏二氟乙烯多孔膜性能的影响

以聚偏二氟乙烯(PVDF)为原料,邻苯二甲酸二丁酯(DBP)和二苯甲酮(DPK)为稀释剂,通过不同的相分离机理(固-液相分离或液-液相分离)制备了不同结构和性能的多孔膜.建立了聚合物/稀释剂体系的二元相图,同时采用扫描电子显微镜(SEM)、孔隙率和水通量测试、差示扫描量热仪(DSC)和X射线衍射仪(XRD)对多孔膜的结...     

热致相分离法制备聚偏氟乙烯微孔膜的微观结构研究

以邻苯二甲酸二丁酯(DBP)和十二醇组成的混合溶剂为稀释剂,采用热致相分离法(TIPS法)制备了聚偏氟乙烯(PVDF)微孔膜.测试了不同体系的固-液相分离温度,研究了稀释剂、冷却条件、聚合物浓度对膜断面微观结构的影响.     

Preparation of porous polyacrylonitrile fibers by electrospinning a ternary system of PAN/DMF/H2O

Polyacrylonitrile (PAN) porous fibers were prepared in one step by electrospinning a ternary system of PAN/N, N-dimethylformamide (DMF)/water at ambient environment. The formation of porous structures was mainly due to the spinodal decomposition phase separation occurred during the electrospinning process. The concentration of PAN varied from 3 to 10 wt.% with the water content changing from 2 to 8 wt.%. When PAN concentration was above 5 wt.%, the composition of the ternary system was close to the “cloud point” and fibers with porous structures were obtained. In addition, the surface tension and viscosity of PAN solutions increased with water which may lead to the diameter increase of the fibers. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers obtained from 8 wt.% PAN solution containing 7 wt.% of water was 46.4 m² g⁻¹, which was 3 times higher than that of nonporous PAN nanofibers prepared under the same conditions from a solution without water.     

高分子量聚丙烯腈中空纤维膜铸膜液流变性能的研究

采用气压式毛细管流变仪对聚丙烯腈/二甲基乙酰胺/聚乙烯吡咯烷酮(PAN/DMAc/PVP)中空纤维铸膜液的流变性能进行了研究.实验结果表明,该铸膜液属假塑型流体.物料性质,如PAN分子量、PAN质量分数、添加剂质量分数会影响体系的流动性能.PAN分子量为Mη=13.1×104、PAN质量分数为14%、添加剂PVP质量分数为10%时,该铸膜液的流动性最好.另外,温度对体系的流动性也有影响.对特定的PAN铸膜体系来说,升高温度使体系的黏度降低,流动性变好;而当体系中PAN分子量增大、PAN质量分数增加时,体系的黏度增大,活化能变大,因而对温度的敏感性也增强.     

低温等离子体液相接枝NVP改性PAN膜

采用液相等离子体接枝技术改性聚丙烯腈(PAN)膜,在PAN膜表面引入亲水性单体氮乙烯吡咯烷酮(NVP).通过傅立叶红外光谱、DSC、XPS对PAN改性膜进行了表征,研究了单体浓度、温度、接枝时间对PAN改性膜纯水通量的影响,考察了在不同单体接枝温度下,PAN改性膜对NaCl、MgSO4混合盐体系的分离性能.     

湿法纺丝Amid-CNT/PAN复合纤维的结构与性能

通过溶液聚合得到胺化碳纳米管（Ami-CNT）/聚丙烯腈（PAN）复合溶液, 采用湿法纺丝技术制备了Amid-CNT/PAN复合纤维。利用红外光谱、 拉曼光谱、 差示扫描量热仪、 热失重仪和扫描电镜等方法分析Amid-CNT对PAN纤维结构的影响。结果表明: Amid-CNT与PAN大分子之间有很强的化学作用力; Amid-CNT在复合纤维中具有很高程度的取向, 使PAN纤维中氰基的取向从1.61提高到了2.30; 复合纤维在空气中的起始放热温度相对PAN纤维从212.30℃提前到206.01℃, 反应放热量从3054J/g降低到2346J/g; 复合纤维比PAN纤维的起始失重温度提前了3.7℃, 在700℃时的剩余质量提高了13.5%; 复合纤维的断面比PAN纤维具有更多的絮状结构。      

Crosslinking of electrospun polyacrylonitrile/hydroxyethyl cellulose composite nanofibers

The electrospinning of polyacrylonitrile (PAN)/hydroxyethyl cellulose (HEC) was performed with glutaraldehyde as a cross linker to fabricate highly hydrophile nanofibers. The concentration of the spinning solution and the ratio of HEC/PAN were varied and adjusted to get smooth nanofibers. The nanofibers were characterized by SEM, FT-IR and contact angle. SEM images showed that the scope of the diameters was 100–300 nm. The nanofibers became thick with the ratio of the HEC/PAN increasing. FT-IR indicated that there could be interactions between HEC and PAN. Contact angle measurement revealed that the increased ratio of HEC and the crosslinking led improvement in the hydrophilicity of PAN/HEC composite nanofibers.     

小分子物质M对聚丙烯腈溶液性质和膜结构的影响

通过小分子物质M对聚丙烯腈(PAN)溶液改性,利用流变仪、紫外可见分光光谱、相变分析、扫描电镜等研究了其对PAN溶液性质、凝固过程及PAN膜结构的影响.结果表明,小分子物质的加入,改变了聚合体系的作用力,PAN溶液的复数黏度提高,低剪切作用下剪切模量提高;小分子物质的加入,提高了聚合物的亲水性,PAN溶液出现浑浊的水用...     

Novel polyacrylonitrile/Na-MMT/silica nanocomposite: Co-incorporation of two different form nano materials into polymer matrix

Polyacrylonitrile (PAN)/Na-montmorillonite (Na-MMT)/SiO₂ nanocomposites were synthesized via in-situ emulsion polymerization. The X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) observations show that the Na-MMT layers were exfoliated in polymerization and the nano materials are well dispersed in the polymer matrix. The thermogravimetric analysis (TGA) suggests that co-incorporating Na-MMT and SiO₂ into the polymer matrix significantly enhances the thermal stability of the polymer. At same nano material loading, the PAN/Na-MMT/SiO₂ nanocomposites show superior thermal stability with respect to the PAN/Na-MMT and PAN/SiO₂ nanocomposites. The mechanical properties of the nanocomposites were also examined. It was found that the PAN/Na-MMT/SiO₂ nanocomposites exhibit considerably enhanced moduli compared with the PAN/Na-MMT and PAN/SiO₂ nanocomposites due to the synergistic reinforcing effect.     

电纺制备聚丙烯腈/聚偏氟乙烯复合纤维膜及其空气过滤性能

以聚偏氟乙烯(PVDF)为芯层,聚丙烯腈(PAN)为皮层,通过同轴法静电纺丝技术制备PAN/PVDF纳米复合纤维膜。通过向纤维膜的皮层中加入纳米硅粉、气相白炭黑、硅溶胶三种不同的纳米粒子和改变皮芯层溶液挤出速度对PAN/PVDF纳米纤维膜进行结构优化。同时,采用BET、SEM、水接触角、纤维强度仪等对纤维膜的孔结构参数、表面形貌、亲水性、力学性能等进行研究。结果表明:在皮层中加入硅溶胶后的溶液导电能力达到32.90 μL/cm,PAN/PVDF纤维膜力学性能最好,纵向断裂强度达到13.02 MPa。含有硅溶胶的口罩布的品质因子达到0.0236,远大于纯聚丙烯(PP)无纺布的品质因子(0.0127),过滤性显著提高。      

CA－PAN－DMAc溶液相转变及凝固过程

通过ＣＡ溶液、ＰＡＮ溶液及两者共混溶液的凝胶固化过程的显微摄影及聚合物－溶剂－沉淀剂的三元相图，揭示了ＣＡ－ＰＡＮ－ＤＭＡｃ溶液的相转变特性及影响共混膜结构和性能的内在因素。结果表明，共混溶液中，ＣＡ和ＰＡＮ以不同的速度发生相转变，由于ＣＡ和ＰＡＮ间的相互作用，使膜断面呈现指状结构和不对称网络结构；相转变点受温度及共混比等条件的影响，膜断面形态亦相应变化；共混膜的水通量和平均孔径均大于纯组分。     

Electrospinning of PAN/DMF/H2O containing TiO2 and photocatalytic activity of their webs

Polyacrylonitrile (PAN) nanofiber webs containing titanium dioxide (TiO₂) were prepared via electrospinning. Either dimethyl formamide (DMF) or its mixture with small amount of water (3 and 5%w/w.) was employed to prepare 5%w/w.PAN/DMF or PAN/DMF/H₂O solution, respectively. Introducing non-solvent water in PAN/DMF/H₂O solution was attempted to induce phase separation, which may lead to formation of porous structure on nanofibers surface. Different amounts of TiO₂ (1 to 3 wt.%) were added into PAN/DMF/(H₂O) solutions and then electrospun into nanofiber webs. From SEM, nanofibers possessed rough surfaces and had averaged diameters in ranges of 170–430 nm., showing tendency to increase with amount of TiO₂ and water. Porous structure on fiber surfaces was not clearly observed, which was suspected to be due to insufficient amount of water employed. Less homogeneity in polymer solution due to presence of TiO₂ disfavored increasing water content higher than 5%w/w. EDS data confirmed presence of TiO₂ in electrospun webs. From photocatalysis evaluation, webs containing 2 and 3 wt.% TiO₂ showed good photocatalytic activity such that 80 percent of 10 ppm. methylene blue degraded in 24 hours. Slight increase in photocatalytic activity was observed in webs obtained from PAN/DMF/H₂O solutions.