Air plasma treatment of polyacrylonitrile porous membrane

The effect of plasma treatment of porous polyacrylonitrile membranes is discussed. It is shown that air plasma increases the surface polarity at low-energy treatment and gradually diminishes it when the energy is increased. When the plasma is set at energies of 12, 30 or 60 W, etching of polymers dominates. Pore diameters of the membranes increase and their distribution functions become broader. When plasma of higher energies (120 or 180 W) is used, the effect of changes of the pore distribution disappears. Membranes modified with plasma of 60, 120 or 180 W do not differ in their porous structure. A simple method of an evaluation of pore diameter distribution function is presented.     

紫外键联马来酸酐表面改性聚丙烯腈超滤膜

采用紫外光法将马来酸酐（MAH）单体键联到聚丙烯腈（PAN）超滤膜表面,考察了紫外光强度、辐射时间、光敏剂浓度以及单体浓度对MAH反应率的影响。采用衰减全反射-傅里叶红外光谱（ATR /FT-IR）、扫描电镜（SEM）和水接触角（CA）对改性膜和原膜进行表征,结果表明单体MAH已成功键联到PAN膜表面,膜表面的亲水性得到提高。蛋白质静态污染以及超滤实验表明马来酸酐键联改性对PAN膜水通量影响不大,但抗污染性能得到明显提高,且由于MAH含有酸酐基团,使PAN膜的可反应性大大提高,使PAN膜易于进一步改性。     

Modification of polyacrylonitrile fibre to reduce combustibility

Flame-resistant PAN fibre was obtained by impregnating the finished fibre with solutions of flame retardants (FR) in different ratios of components. The oxygen index of the modified samples increased to 34.5 vol. %. The presence of a reaction between the PAN fibre and the FR due to both chemical and van der Waals and hydrogen bonds was established by calculating the effectiveness factor of the sorption reaction. The effect of FR on pyrolysis of the modified fibres was investigated. Cyclization processes began in the modified fibre at lower temperatures than for the initial PAN fibre, took place at a lower rate, and were accompanied by a high yield of coke residue. Translated from Khimicheskie Volokna, No. 6, pp. 17–19, November-December, 2008.     

Modification of polyacrylonitrile fibres with halogen-containing polymers

Conclusions The physicomechanical and relaxation properties of fibres based on mixtures of polyacrylonitrile with halogen-containing polymers — polyvinyl chloride, chlorinated polyvinyl chloride, and Ftorlon — have been studied.It has been found that on introducing small additions of HCP, the physicomechanical properties of the fibres rise in an extreme fashion.Translated from Khimicheskie Volokna, No. 2, pp. 44–45, March–April, 1984.     

Modification of polyacrylonitrile fibre with hydrolyzed wastes

Conclusions Principles governing the alkaline hydrolysis of wet Nitron fibre waste and their solubilities in 51.5% aqueous sodium thiocyanate solution have been studied. It has been found that the best solubility is attained at an SEC of 0.17–0.20 meq/g. The solutions obtained on addition of these wastes are characterized by reduced viscosity, better filterability, and a reduced gel-particle content.It has been found that stable spinning and preparation of fibre with better physicomechanical characteristics are achieved when 5% by wt. of the hydrolyzed products is added to the spinning solution.Translated from Khimicheskie Volokna, No. 1, pp. 10–11, January–February, 1989.     

Synthesis of emulsion-templated porous polyacrylonitrile and its pyrolysis to porous carbon monoliths

PolyHIPEs are emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). The miscibility of acrylonitrile (AN) with water has made it difficult to synthesize PAN-based polyHIPEs. This paper describes the successful synthesis of PAN-based polyHIPEs by crosslinking through copolymerization with divinylbenzene (DVB), by stabilization with a polyglycerol polyricinoleate surfactant, and by initiation with both oil- and water-soluble initiators. The PAN-based polyHIPEs had porosities of over 86% and porous structures that were different from those of typical polyHIPEs. This paper also describes the production of porous carbon monoliths through the pyrolysis of these PAN-based polyHIPEs. Pyrolysis did not produce significant changes in the porous structures, which were quite similar to those of the original polyHIPEs. The porosities were around 95% and the carbon monoliths were largely macroporous and mesoporous, with some microporosity. These results indicate that PAN-based polyHIPE templates can be used for the a priori design of porous carbon monoliths.     

Surface modification of polyacrylonitrile based ultrafiltration membrane

Ultrafiltration membrane based on polyacrylonitrile prepared by phase inversion method using zinc chloride as an additive showed more than 90% rejection for BSA and 90–110 lm^?2 h^?1 water flux. The surface modification of this membrane was studied using ethanolamine, triethylamine, sodium hydroxide, and potassium hydroxide solutions. The effect of base treatment time and temperature on water flux and rejection was investigated. The membranes exhibited swelling by NaOH treatment followed by deswelling by HCl post‐treatment, similar to pH responsive membranes. The treatment by organic as well as inorganic bases improved water flux with a slight lowering in BSA rejection by dead‐end mode type treatment. A 230% increase in water flux was achieved by sodium hydroxide treatment in crossflow mode without a noticeable pore swelling by SEM. The contact angle of the modified membranes was decreased as compared to the unmodified one indicating appreciable surface modification. As the treatment time or temperature increased, the ESCA analysis showed increased population of Na‐carboxylate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4378–4385, 2006     

大分子抗菌剂前驱体共混改性聚丙烯腈纤维

通过水相沉淀聚合方法制备了3-烯丙基-5,5-二甲基己内酰脲/丙烯腈共聚物。将不同配比的共聚物和聚丙烯腈溶解于硫氰酸钠水溶液中配成纺丝液,采用两步法纺制了聚丙烯腈共混纤维。随共聚物含量增加,共混纤维的强度略有降低,断裂伸长率增加;而共混纤维的比电阻和热分解温度降低。仅含质量分数10％共聚物的共混纤维经氯漂后,对大肠杆菌的杀灭率可达97.5％。     

Low-surface-free-energy polybenzoxazine/polyacrylonitrile fibers for biononfouling membrane

We blended poly(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine) (PBA) into polyacrylonitrile (PAN) to generate low-surface-free-energy fibers without fluorine and silicon elements for electrospinning. Liquid-state BA at room temperature can be solidified in electrospinning process using PAN as a medium through their miscible behavior. Results indicate that the mixing below 50 wt% BA into PAN matrix for electrospinning has no significant dropping beads, indicated a miscible PAN/BA system. Above 70 wt% BA in PAN solution could not be solidified completely after electrospinning, revealed apparent beaded fibers. The PAN/PBA blend fibers, obtained after curing at 300 °C, generated a superhydrophobicity because of the low-surface-free-energy PBA. In addition, laser scanning confocal microscope (LSCM) measurements were included to determine the relative amount of antibody that adsorbed to these PAN/PBA fibers to examine the biofouling-resistant property. The results showed an obviously decreased protein adsorption with increasing PBA fraction. The correlations between PAN and PBA would provide insight into the designing and developing of low-surface-free-energy fibers without fluorine and silicon elements to improve biofouling-resistant property.     

Performance evaluation of polyvinylchloride/polyacrylonitrile ultrafiltration blend membrane

Polyvinylchloride (PVC) membranes were modified by blending with polyacrylonitrile (PAN) as a second polymer. The miscibility of PVC/PAN blend was examined using an incompressible regular solution (CRS) model in no need to make a membrane. The results showed that the PVC/PAN blend was immiscible for all compositions at a temperature range of ?25 to 225 °C. Furthermore, the prediction of the phase behavior of a PVC/PAN/DMF ternary system showed that the blend of two polymers was highly incompatible even in their common DMF solvent. However, this incompatibility led to a remarkable increase in the porosity of the blend membrane and pure water flux compared to those for pure PVC membrane. The pure water flux of the PVC membrane (37.9 ± 1.5 L/m² h) increased about 41 and 76% by adding 10 and 20 wt% PAN, respectively. The blend membranes also showed an enhanced flux recovery ratio (FRR) compared to a pure PVC membrane, although the PVC membrane rejection for Bovine serum albumin (BSA) was decreased after blending with PAN. The PVC/PAN (90/10) blend membrane was subjected to hydrolysis with NaOH alkaline solution at three different concentrations and contact times to further enhance its performance. The membrane, which was hydrolyzed with a 0.5 mol/L NaOH solution for 0.5 h, showed a highest pure water flux of 75.6 ± 7.2 L/m² h due to its increased hydrophilicity. This membrane also revealed an improved FRR and better thermal and mechanical properties compared to an unmodified membrane.     

Adsorption of heavy metal ions from aqueous solutions by porous polyacrylonitrile beads

The adsorption of Cu(II), Ni(II), Zn(II), and Pb(II) from aqueous solutions on acrylonitrile copolymer sorbents was studied. We prepared five types of sorbents from polyacrylonitrile by varying its concentration in the initial polymer solution and the composition of the coagulation bath, aiming to achieve a different porous structure. The specific area, pore volume, and pore radius of the sorbents were determined on a porosimeter. The porous structure was studied by scanning electron microscopy. Modification of sorbents with sodium hydroxide and hydroxylamine was carried out to form amidooxyme and carboxylic groups with proven complex‐forming properties toward heavy metal ions. The optimal pH of the sorption of metal ions was found. The adsorption kinetics were investigated. The order of polymer sorbents toward the sorption of Pb(II), Cu(II), Ni(II), and Zn(II) ions, and the order of heavy metal uptake were determined for all types of sorbents. The effectiveness of heavy metal desorption and the coefficient of recovery of sorption ability were determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3036–3044, 2002; DOI 10.1002/app.2334     

聚醚砜／聚丙烯腈共混膜的制备及性能表征

以聚醚砜(PES)和聚丙烯腈(PAN)为膜材料,通过液-固相转化法制备PES/PAN共混膜.研究了制膜过程中的几个主要因素对膜孔径、孔隙率、纯水通量、牛血清蛋白(BSA)截留率以及膜微观结构的影响.通过正交实验结果分析,得到优化的制膜条件为:PES和PAN总质量分数为16%,m(PES):m(PAN)=8:2,添加剂为氯化锂(LiCl)和聚乙烯吡咯烷酮(PVP),LiCl和PVP总质量分数为8%,m(LiCl):m(PVP)=2:8.在压力0.2 MPa条件下,所制备的PES/PAN膜的纯水通量为320.57L/m2·h,高出PES膜近1倍,BSA截留率变化不大.     

Modification of porous copolymers network based on acrylonitrile

Summary The preparation of a chelating ion-exchange network based on acrylonitrile was carried out by chemical modification with hydroxylamine. The beads of resin were synthesized by aqueous suspension copolymerization of acrylonitrile (AN), styrene (STY) and divinylbenzene (DVB). The influence of diluent used in the suspension polymerization on the structure of the resulting copolymers was evaluated. The diluents employed were heptane (HEP), toluene (TOL) and anisole (ANI). It was found that the AN incorporation into copolymer structure was dependent on the diluent used. Conversion of nitrile groups into the amidoxime was conducted by treatment with hydroxylamine under alkaline solution. The resins were characterized by apparent density, surface area, average pore diameter, elemental analysis (CHN), FTIR and optical microscopy. Based on the results obtained, it was possible to control the porosity by diluent employed in the synthesis and to modify chemically a resin containing nitrile groups by hydroxylamine reaction. Received: 6 October 2001/Revised version: 2 April 2002/ Accepted: 11 April 2002     

Wood-inspired polyacrylonitrile foam with hierarchically aligned porous structure for application in water purification

The main purpose of this study is to verify the excellent absorption efficiency of polyacrylonitrile (PAN) foam which has a hierarchically aligned porous structure similar to wood for water purification. Ice template and freeze drying method was employed to prepare the PAN foam, and the performance of the prepared sample was characterized by advanced technology. Experimental data revealed that the micromorphology, absorption efficiency, and mechanical properties were tunable by controlling the polymer concentration in solution. The PAN foam prepared at 7 wt% not only had excellent absorption efficiency, but also had great water flux. The highest absorption efficiency of the PAN foam prepared at 7 wt% for the model dye, methylene blue, reached 97.83%. Therefore, a new strategy for water purification by filtration using a scaffold with a hierarchically aligned porous structure is possible.