气流-静电纺丝法制备苯乙烯-丁二烯-苯乙烯嵌段共聚超细纤维

采用75%四氢呋喃(THF)和25%N,N-二甲基甲酰胺(DMF)的混合溶液作溶剂,通过气流-静电纺丝法制备了苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)超细纤维。利用扫描电镜(SEM),研究了溶液浓度、电压、接收距离(喷丝孔到接收板的距离)、喷丝孔内径对静电纺纤维的直径和形貌的影响。研究发现:溶液浓度对电纺纤维的直径和形貌有非常重要的影响,当溶液浓度由10%增加到18%时,电纺纤维平均直径随之成线性增加;当电压由23.8kV增加到33.8kV时,纤维平均直径先减小后增加。最佳工艺条件为:溶液质量分数为14%,电压为28.8kV,接收距离为20cm,喷丝孔内径为0.27mm,所得SBS电纺超细纤维平均直径为429nm。     

Electrospinning of polycarbonate urethane biomaterials

Polycarbonate urethane (PCU) nano-fibers were fabricated via electrospinning using N,N- dimethylformamide (DMF) and tetrahydrofuran (THF) as the mixed solvent. The effect of volume ratios of DMF and THF in the mixed solvent on the fiber structures was investigated. The results show that nano-fibers with a narrow diameter distribution and a few defects were obtained when mixed solvent with the appropriate volume ratio of DMF and THF as 1∶1. When the proportion of DMF was more than 75% in the mixed solvent, it was easy to form many beaded fibers. The applied voltage in the electrospinning process has a significant influence on the morphology of fibers. When the electric voltage was set between 22 and 32 kV, the average diameters of the fibers were found between 420 and 570 nm. Scanning electron microscopy (SEM) images showed that fiber diameter and structural morphology of the electrospun PCU membranes are a function of the polymer solution concentration. When the concentration of PCU solution was 6.0 wt-%, a beaded-fiber microstructure was obtained. With increasing the concentration of PCU solutions above 6.0 wt-%, beaded fiber decreased and finally disappeared. However, when the PCU concentration was over 14.0 wt-%, the average diameter of fibers became large, closed to 2 μm, because of the high solution viscosity. The average diameter of nanofibers increased linearly with increasing the volume flow rate of the PCU solution (10.0 wt-%) when the applied voltage was 24 kV. The results show that the morphology of PCU fibers could be controlled by electrospinning parameters, such as solution concentration, electric voltage and flow rate.     

Solution blowing of thermoplastic polyurethane nanofibers: A facile method to produce flexible porous materials

Solution blowing (SB) is a promising and scalable approach for the production of nanofibers. Air pressure, solution flow‐rate, and nozzle‐collector distance were determined as effective process parameters, while solution concentration was also reported as a material parameter. Here we performed a parametric study on thermoplastic polyurethane/dimethyl formamide (TPU/DMF) solutions to examine the effect of such parameters on the resultant properties such as fiber diameter, diameter distribution, porosity, and air permeability of the nanofibrous webs. The obtained solution blown thermoplastic polyurethane (TPU) nanofibers had average diameter down to 170 ± 112 nm, which is similar to that observed in electrospinning. However, the production rate per nozzle can be 20 times larger, which is primarily dependent on air pressure and solution flow rate (20 mL/h). Moreover, it was even possible to produce nanofibers polymer concentrations of 20%; however, this increased the average nanofiber diameter. The fibers produced from the TPU/DMF solutions at concentrations of 20% and 10% had average diameters of 671 ± 136 nm and 170 ± 112 nm, respectively. SB can potentially be used for the industrial‐scale production of products such as nanofibrous filters, protective textiles, scaffolds, wound dressings, and battery components. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43025.     

The use of Weber number to predict morphology in the electrospinning of poly(ethylene oxide) nanofibers

In the electrospinning of polymer nanofibers, an electrically driven jet of polymer solution travels to a grounded target to be collected. The morphology of the resulting nanofibers can be manipulated through process parameters, though little work has been done to correlate electrospinning parameters with those of the free‐jet flow of pure liquids. This is essential when the nanofibers hold entrained beaded structures indicative of jet breakup. The effects of applied voltage and solution concentration on the fiber morphology of electrospun aqueous solutions of poly(ethylene oxide) were investigated. Solution concentrations of 4–8 wt % were used along with voltages of 4.5–11 kV to produce nanofibers with and without entrained beads. It was determined that the calculated Weber number for each condition correlated well with the resulting morphology. These results may suggest that Weber number may also be used to predict nanofibers morphology in the electrospinning of other polymer systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

气流-静电纺丝法制备聚对苯二甲酸乙二酯纳米纤维

采用50%苯酚和50%1,1,2,2-四氯乙烷的混合溶液为溶剂,通过气流-静电纺丝法制备了聚对苯二甲酸乙二酯(PET)纳米纤维。利用扫描电镜(SEM),研究了聚合物分子质量、溶液浓度、电压、接收距离(喷丝孔到接收板的距离)对电纺纤维形态结构的影响。结果表明:随着聚合物分子质量和溶液浓度增加,纤维平均直径也随之增加;纤维平均直径随电压的增加而减小;随接收距离的增加,纤维平均直径先减小后增加。最佳工艺条件为:聚合物特性黏度为0.818 dL/g,溶液质量分数为15%,电压为32 kV,接收距离为23 cm,所得PET电纺纳米纤维平均直径为85 nm。     

Polymeric nanofibers via flat spinneret electrospinning

Electrospun nanofibers are most often produced by needle electrospinning process, which has inherent disadvantages like clogging and low efficiency. In this study, an alternative needleless electrospinning process is reported for the fabrication of nanofibers based on a novel spinneret. Firstly, a spinneret with a 0.5‐mm diameter hole in the middle of a flat plastic cap was custom‐made that may be readily scaled up for mass production. Then, polyethylene oxide (PEO) aqueous solution with 6.0 wt% concentration was used to demonstrate the needleless electrospinning process. The processing window for the jet formation in the flat spinneret electrospinning process was determined. The relationships between various processing parameters (applied voltage, working distance, and flow rate) and the resultant PEO nanofibers were also investigated. It was found that stable fluid jet launched from the tip of the coned droplet anchored at the rim of the hole and formed fibers. The morphology and diameter of electrospun fibers were examined using scanning electron microscopy. The results show that PEO nanofibers produced by this needleless electrospinning have similar structure and morphology to those from the single needle source. Finally, the hole number of spinneret was increased to four holes, which was still able to produce smooth nanofibers with a higher production rate. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Foam electrospinning: A multiple jet,needle‐less process for nanofiber production

A multiple jet, needle‐less process to fabricate electrospun nanofibers from foamed columns, produced by injecting compressed gas through a porous surface into polymer solutions, capable of circumventing syringe electrospinning shortcomings such as needle clogging and restrictions in production rate is presented. Using polyvinyl alcohol and polyethylene oxide (PEO) as model systems, we identify key design, processing, and solution parameters for producing uniform fibers. Increasing electrode surface area produces thicker mats, suggesting charge distribution through the bulk foam facilitates electrospinning. Similar trends between foam and syringe electrospinning are observed for collection distance, electric field strength, and polymer concentration. Interestingly, the empirical correlation between polymer entanglement and fiber formation are found to be similar for both foam and traditional needle electrospinning, but the fiber crystallinity shows enhancement with foam electrospinning. In addition, foam electrospinning with a PEO‐nonionic surfactant system yields two orders of magnitude increase in production rate compared to syringe electrospinning. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1355–1364, 2014     

Concept of minimum electrospinning voltage in electrospinning of polyacrylonitrile N,N‐dimethylformamide system

Polyacrylonitrile solutions in N,N‐dimethylformamide (DMF) were electrospun into nanofibers by charging the polymer fluid in an electric field. Controlled experiments were performed using a needle type spinneret to investigate the effect of various electrospinning parameters on the percentage conversion of polymeric fluid into fibers and on fiber diameter obtained. It was found that when the polymeric fluid was continuously fed at a constant rate, application of a minimum electrospinning voltage (MEV) was necessary to “completely” convert the ejected fluid into nanojets to form nanofibers. Also, that the maximum amount of splitting or elongation that a polymeric fluid could undergo was primarily dependent on number of entanglements per chain in the fluid. This resulted in obtaining nanofibers with a particular diameter irrespective of the values of important electrospinning variables such as applied voltage, flow rates, and distance between the electrodes. On the other hand, MEV, necessary to obtain full conversion into nanofibers, was found to be strongly dependent on the spinning parameters and was unique for a given set of parameters. The significance of the MEV was evident from the fact that the square of the MEV, which is a measure of the electrical energy utilized by the system, was found to be directly proportional to the rate of formation of fiber surface area during the electrospinning process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚醚砜的静电纺丝研究

采用聚醚砜(PES)的良溶剂二甲基甲酰胺(DMF)和非良溶剂丙酮(AC)为共溶剂体系,研究了溶剂组成、纺丝成形条件对静电纺丝PES纤维的形貌及纤维直径的影响。结果表明:DMF/AC的配比对于静电纺丝PES纤维形貌具有直接的调控作用,随着DMF/AC混合溶剂中AC用量的增加,纤维平均直径变大,纤维毡中串珠数目明显减少,纤维均一性变好;随着纺丝液浓度的升高,纺丝电压的增大,纤维的平均直径变大;接收距离的变化对纤维平均直径影响不大;PES最佳纺丝工艺条件为纺丝溶液质量分数13%,纺丝电压15 kV,接收距离10 cm,mDMF/mAC为8.5/1.5,在此条件下,可以获得纤维平均直径为96 nm的PES纤维毡。     

Effect of air blowing on the morphology and nanofiber properties of blowing‐assisted electrospun polycarbonates

Polycarbonate (PC) nanofibers are prepared using the air blowing‐assisted electrospinning process. The effects of air blowing pressure and PC solution concentration on the physical properties of fibers and the filtration performance of the nanofiber web are investigated. The air blowing‐assisted electrospinning process produces fewer beads and smaller nanofiber diameters compared with those obtained without air blowing. Uniform PC nanofibers with an average fiber diameter of about 0.170 μm are obtained using an applied voltage of 40 kV, an air blowing pressure of 0.3 MPa, a PC solution concentration of 16%, and a tip‐to‐collection‐screen distance (TCD) of 25 cm. The filtration efficiency improvement of the air blowing‐assisted electrospun web can be attributed to the narrow distribution of fiber diameter and small mean flow pore size of the electrospun web. Performance results show that the air blowing‐assisted electrospinning process can be applied to produce PC nanofiber mats with high‐quality filtration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Solution blow spinning: A new method to produce micro‐ and nanofibers from polymer solutions

A solution blow spinning technique was developed using elements of both electrospinning and melt blowing technologies as an alternative method for making non‐woven webs of micro‐ and nanofibers with diameters comparable with those made by the electrospinning process with the advantage of having a fiber production rate (measured by the polymer injection rate) several times higher. The diameters of fibers produced ranged from 40 nm for poly(lactic acid) to several micrometers for poly(methyl methacrylate). This solution blow spinning method uses a syringe pump to deliver a polymer solution to an apparatus consisting of concentric nozzles whereby the polymer solution is pumped through the inner nozzle while a constant, high velocity gas flow is sustained through the outer nozzle. Analysis of the process showed that pressure difference and shearing at the gas/solution interface jettisoned multiple strands of polymer solution towards a collector. During flight, the solvent component of the strands rapidly evaporates forming a web of micro and nanofibers. The effect of injection rate, gas flow pressure, polymer concentration, working distance, and protrusion distance of the inner nozzle was investigated. Polymer type and concentration had a greater effect on fiber diameter than the other parameters tested. Injection rate, gas flow pressure, and working distance affected fiber production rate and/or fiber morphology. Fibers were easily formed into yarns of micro‐ and nanofibers or non‐woven films that could be applied directly onto biological tissue or collected in sheets on a rotating drum. Indeed, virtually any type of target could be used for fiber collection. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Efficient preparation of polymer nanofibers by needle roller electrospinning with low threshold voltage

A novel electrospinning system with needle roller as spinneret for efficient preparation of nanofibers was proposed. The results of finite element simulation indicate that the electric field is more concentrated at the tip of needle piece compared with that for disc and coil spinnerets, which can effectively reduce the threshold voltage of electrospinning. Using polyvinyl alcohol (PVA) as model polymer, the effects of spacing between needle pieces and concentration of spinning solution on fiber diameter and productivity of nanofibers were investigated. The results indicate that the average diameter decreases and the uniformity of diameter increases when increasing the spacing between needle pieces. When the spacing between the needle pieces is 14 mm, the average and standard deviation (SD) of fiber diameter is as small as 190 and 72 nm, respectively. The productivity of nanofibers slightly increases with the concentration of spinning solution, and it is as high as 12.8 g/h when the PVA concentration was 11 wt% for a needle piece spacing of 10 mm, which is much higher than the productivities of reported electrospinning systems. The proposed system has the potential for the preparation of uniform nanofibers with increased throughput and reduced cost. POLYM. ENG. SCI., 59:745–751, 2019. © 2018 Society of Plastics Engineers     

Electric current as a control variable in the electrospinning process

In the electrospinning process submicron‐diameter polymer fibers can be produced when a high potential difference is applied to a polymer drop suspended at the tip of a capillary. The electrospinning process is affected by a wide range of parameters, because of which controlling the properties of the fibers is difficult. This is the major hurdle in the development of practical applications of electrospun fibers along with its low productivity. Here we are proposing to use the electric current in the electrospinning process to control the “quality of the fibers”. Electrospinning of a solution of polyacrylonitrile in dimethylformamide (PAN/DMF) was done by applying a programmed variable flow rate at different constant voltages. The electric current in the process was measured in real time. Four types of jet regimes were observed, electric current and the morphology of the fibers corresponding to these regimes were analyzed. A relation between the electric current, type of jet and morphology of the fibers has been established. The mechanical properties of electrospun fiber mats were also measured by a tensile testing method. POLYM. ENG. SCI. 46:954–959, 2006. © 2006 Society of Plastics Engineers     

Investigation on jet stability,fiber diameter,and tensile properties of electrospun polyacrylonitrile nanofibrous yarns

Electrospinning is a flexible and efficient method for producing nanofibers by using relatively dilute polymer solution. However, there are many parameters related to material and processing that influence the morphology and property of the nanofibers. This study investigates the influence of electric field and flow rate on diameter and tensile properties of nanofibers produced using polyacrylonitrile (PAN)‐dimethylformamide (DMF) solution. Stability of the spinning jet is investigated via fiber current measurement and an image system at different electric fields and solution flow rates. It is observed that a set of electric field and flow rate conditions favor producing thinnest, strongest, and toughest nanofibers during electrospinning process. Other conditions may lead to instability of the Taylor cone, discontinuous jet, larger diameter fiber, and lower mechanical properties. Finally, a simple dynamic whipping model is adopted to correlate the nanofiber diameter with volumetric charge density and is found to be excellent validating our experimental results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41918.     

Double‐nozzle air‐jet electrospinning for nanofiber fabrication

A novel double‐nozzle air‐jet electrospinning apparatus was developed to fabricate nanofibers on a large scale. The distribution of the electric field at different nozzle distances was simulated to analyze the jet path, productivity, and deposition area of nanofiber webs and the nanofiber morphology. Our experiments showed that the bubbles usually ruptured intermittently on the top surface of the two nozzles and the jets traveled in a straight path with a high initial velocity. A continuous and even thickness of the nanofiber webs were obtained when the nozzle distances was less than 55 mm. At nozzle distances of 55 mm, the received fibers were thin with the lowest standard deviation. Experimental parameters involving the applied voltage, collecting distance, and air flow rate were also investigated to analyze the nanofiber morphology at a nozzle distance of 55 mm. The results show that the nanofibers presented a finer and thinner diameter at an applied voltage of 36 kV, a collecting distance of 18 cm, and an air flow rate of 800 mL/min. The nanofiber production of this setup increased to nearly 70 times that with a single‐needle electrospinning setup. On the basis of the principle of this air‐jet electrospinning setup, various arrangements of multinozzle electrospinning setups could be designed for higher throughput of nanofibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40040.     

Transparent poly(methyl methacrylate‐co‐butyl acrylate) nanofibers

Nanofibers of n‐Butyl Acrylate/Methyl Methacrylate copolymer [P(BA‐co‐MMA)] were produced by electrospinning in this study. P(BA‐co‐MMA) was synthesized by emulsion polymerization. The structural and thermal properties of copolymers and electrospun P(BA‐co‐MMA) nanofibers were analyzed using Fourier transform infrared spectroscopy–Attenuated total reflectance (FTIR–ATR), Nuclear magnetic spectroscopy (NMR), and Differential scanning calorimetry (DSC). FTIR–ATR spectra and NMR spectrum revealed that BA and MMA had effectively participated in polymerization. The morphology of the resulting nanofibers was investigated by scanning electron microscopy, indicating that the diameters of P(BA‐co‐MMA) nanofibers were strongly dependent on the polymer solution dielectric constant, and concentration of solution and flow rate. Homogeneous electrospun P(BA‐co‐MMA) fibers as small as 390 ± 30 nm were successfully produced. The dielectric properties of polymer solution strongly affected the diameter and morphology of electrospun polymer fibers. The bending instability of the electrospinning jet increased with higher dielectric constant. The charges inside the polymer jet tended to repel each other so as to stretch and reduce the diameter of the polymer fibers by the presence of high dielectric environment of the solvent. The extent to which the choice of solvent affects the nanofiber characteristics were well illustrated in the electrospinning of [P(BA‐co‐MMA)] from solvents and mixed solvents. Nanofiber mats showed relatively high hydrophobicity with intrinsic water contact angle up to 120°. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4264–4272, 2013     

Preparation of atactic poly(vinyl alcohol)/silver composite nanofibers by electrospinning and their characterization

Poly(vinyl alcohol) (PVA)/silver composite nanofibers were successfully prepared by the electrospinning method. Water‐based colloidal silver in a PVA solution was directly mixed without any chemical or structural modifications into PVA polymer fibers to form organic–inorganic composite nanofibers. The ratio of silver colloidal solution to PVA played an important role in the formation of the PVA/silver composite nanofibers. We prepared two different atactic PVA/silver nanocomposites with number‐average degrees of polymerization of 1700 and 4000 through electrospinning with various processing parameters, such as initial polymer concentration, amount of silver colloidal solution, applied voltage, and tip‐to‐collector distance. The PVA/silver composite nanofibers were characterized by field emission scanning electron microscopy and transmission electron microscopy (TEM). TEM images showed that silver nanoparticles with an average diameter of 30–50 nm were obtained and were well distributed in the PVA nanofibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrospinning of uniform polystyrene fibers: The effect of solvent conductivity

By means of the electrospinning technique, micron- and nanofibers can be obtained from polymer solutions under a very high electrical field. A special challenge is to produce bead-free uniform fibers since any minor changes in the electrospinning parameters such as slight variations in the polymer solutions and/or electrospinning experimental parameters may result in significant variations in the final nanofiber morphology. Furthermore, it is often not trivial at all to obtain reproducible uniform electrospun nanofibers for the optimized electrospinning conditions. Here we report that the conductivity of the solvent is the key factor for the reproducible electrospinning of uniform polystyrene (PS) fibers from dimethylformamide (DMF) solutions. It is shown that even slight changes in the conductivity of the DMF solutions can greatly affect the morphology of the resulting electrospun PS fibers. Here, we have carried out a thorough and systematic study on the effect of solution conductivity on the electrospinning of bead-free polystyrene (PS) fibers when dimethylformamide (DMF) was used as the solvent. Interestingly, we found out that different grades of solvent as-received (DMF) from various suppliers have slightly different solution conductivities. Consequently, the polymer solutions prepared with the same PS concentration have different conductivities, which are shown to have significant changes on the morphology of the PS fibers resulting in beaded or bead-free uniform fibers when electrospun under the identical electrospinning conditions. Such as, bead-free PS fibers were obtained from PS solutions in the range of 20% (w/v) through 30% (w/v) depending on the DMF grade used. In brief, it was observed that solutions with a higher conductivity yielded bead-free fibers from lower polymer concentrations, which confirms that the solution conductivity plays a very significant role in producing bead-free uniform PS fibers.     

Needleless Electrospinning from a Tube with an Embedded Wire Loop

Enhancing the production rate while maintaining control in electrospinning has been a challenge for years. This work proposes a novel spinneret from a tube with a single wire loop embedded in its one end. With the feeding of solution precisely controlled and the spinning process stablized, multiple polymer jets can be continuously generated from the wire loop. The as‐spun fibers show nanofibrous structure and its fiber diameter is greatly affected by the applied voltage and polymer concentration. As compared to needle electrospinning, the wire loop spinneret generates a stronger electric field with a larger spinnable area due to its special geometrical structure and a higher applied voltage it is connected to. Slightly coarser nanofibers are fabricated as compared to the nanofibers from needle electrospinning and the production rate is as high as 0.48 g h^?1.     

Influence of processing conditions on polymorphic behavior,crystallinity, and morphology of electrospun poly(VInylidene fluoride) nanofibers

The polymorphism and crystallinity of poly(vinylidene fluoride) (PVDF) membranes, made from electrospinning of the PVDF in pure N,N‐dimethylformamide (DMF) and DMF/acetone mixture solutions are studied. Influence of the processing and solution parameters such as flow rate, applied voltage, solvent system, and mixture ratio, on nanofiber morphology, total crystallinity, and crystal phase content of the nanofibers are investigated using scanning electron microscopy, wide‐angle X‐ray scattering, differential scanning calorimetric, and Fourier transform infrared spectroscopy. The results show that solutions of 20% w/w PVDF in two solvent systems of DMF and DMF/acetone (with volume ratios of 3/1 and 1/1) are electrospinnable; however, using DMF/acetone volume ratio of 1/3 led to blockage of the needle and spinning process was stopped. Very high fraction of β‐phase (～79%–85%) was obtained for investigated nanofiber, while degree of crystallinity increased to 59% which is quite high due to the strong influence of electrospinning on ordering the microstructure. Interestingly, ultrafine fibers with the diameter of 12 and 15 nm were obtained in this work. Uniform and bead free nanofiber was formed when a certain amount of acetone was added in to the electrospinning solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42304.