Nanofibers from recycle waste expanded polystyrene using natural solvent

Summary A new recycling technique has been developed. In this method, EPS (expanded polystyrene), generally called Styrofoam, is dissolved with natural solvent, d-limonene and electrospun. This method can economically produce the nanofibers. The electrospinning process produces a nonwoven mat of long polymer fibers with diameters in the range of 10–500 nm and high surface areas per unit mass. PS (Polystyrene) polymer dissolved in different solvents such as THF (Tetrahydrofuran), DMF (Dimethylformaide), and DMAc (Dimethylacetamide) etc. may all be electrospun into nanofibers. These solvents cause environmental problem and difficulty of process handling. Natural solvent, d-limonene is used for dissolving PS. PS nanofibers are produced with PS solution using d-Limonene. This paper describes the use of polystyrene (PS) nanofibers electrospun from recycled EPS solution dissolved in d-limonene. The electrospun polystyrene nanofiber diameters vary from 300 to 900 nm, with an average diameter of about 700 nm.     

Processing and characterization of electrospun poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) nanofibrous membranes

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) nanofibrous membranes were first fabricated via electrospinning from chloroform (CHCl₃) or CHCl₃/dimethylformamide (DMF) polymer solutions. The electrospinning conditions such as the polymer concentration, the solvent composition, and the applied voltage were optimized in order to get smooth and nano-sized fibers. The crystalline structure, the melting behaviors and the mechanical properties of the obtained nanofibrous membranes were characterized. With pure CHCl₃ as the solvent in the electrospinning process, the finest smooth PHBHHx fibers were about 1 μm in diameter. When DMF is added to CHCl₃ as a co-solvent, the conductivity and volatility of the solution increased and reduced, respectively, and the electrospinnability of the polymer solution increased as a result. The averaged diameters of PHBHHx fibers could be reduced down to 300-500 nm when the polymer concentration was kept at 3 wt%, the ratio of DMF/CHCl₃ was maintained at 20/80 (wt%), and the applied voltage was fixed at 15 kV during electrospinning. WAXD and DSC results indicated that the crystallization of the PHBHHx nanofibers was restricted to specific crystalline planes due to the molecular orientation along the axial direction of the fibers. The crystallization behaviors of the electrospun nanofibers were significantly different from that of the cast membranes because of the rapid solidification and the one-dimensional fiber size effect in the electrospinning process. Mechanically, the electrospun PHBHHx nanofibrous membranes were soft but tough, and their elongation at break averaged 240-300% and could be up to 450% in some cases. This study demonstrated how the size of electrospun PHBHHx fibers could be reduced by adding DMF in the solvent and gave a clue of the presence of oriented molecular chain packing in the crystalline phase of the electrospun PHBHHx fibers.     

The morphology,mechanical properties,and flammability of aligned electrospun polycarbonate (PC) nanofibers

The electrospinning of the polycarbonate (PC) solutions was performed for the variable electrospinning parameters such as polymer concentration, solvent composition, applied voltage, flow rate, and take‐up velocity in order to evaluate changes of morphology, mechanical properties, and flammability of the aligned PC nanofibers as a function of the electrospinning parameters. It was found that the ratio of THF/DMF solvent in the electrospinning parameters had a major effect on the spinnability and fiber morphology. Furthermore, it was confirmed that the mechanical properties were dependent upon the fiber morphology. The spinnability of the PC solutions with a lower THF ratio in THF/DMF solvent was poor. The aligned electrospun PC fiber with the best morphology was made in the range of polymer concentration of 22%, solvent ratio of 50:50 THF : DMF, applied voltage of 14 kV, flow rate of 0.050 ml/m, and a take‐up velocity of 7.3 m/s. The ultimate strength and initial modulus of the 80% drawn 22% PC fiber were 64 ± 2 MPa (commercial 55–75 MPa) and 1.9 ± 0.1 GPa. The heat release capacity (HRC) of the 22 and 25% PC fiber were 275 ± 27 J/g K and 198 ± 1 J/g K. It was found that the flame resistance of the electrospun PC nanofiber was superior to that of the PC raw material (HRC ～360 J/g K). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Construction of hierarchical structures by electrospinning or electrospraying

To expand the application of electrospun fibers or electrosprayed beads, micro-nano hierarchical structures of polystyrene (PS) have been constructed through the adjustment of solvent, polymer concentration, environment humidity, electrospinning temperature, etc. Primary structures, such as fibers, beads and bead-on-string structure, as well as secondary structures, such as nanopores, nanopapilla and net-work structure, have been constructed. Solvent plays an important role in the construction of both primary structures and secondary structures. By using N,N-dimethylformamide (DMF), tetrahydrofuran (THF) and mixed solvent of DMF/THF, the micro-nano hierarchical structures can be controlled. Humidity is a key factor to the construction of secondary structures. The obtained fibers or beads have smooth surface at low humidity. While at high humidity, secondary structures tend to appear. For the PS/DMF system, vapor-induced phase separation may be the most pertinent mechanism to explain the formation of secondary structures. While for the PS/THF system, breath figure theory can explain the formation of uniform nanopores properly.     

Effect of solvent quality and humidity on the porous formation and oil absorbency of SAN electrospun nanofibers

In this study, nanofibrous mat with high oil sorption capability was prepared via one‐step electrospinning process without any further post‐treatments. For this purpose, the fabrication of styrene/acrylonitrile copolymer nanofibers was carried out using various dimethylformamide (DMF)/tetrahydrofuran and DMF/ethanol (DMF/EtOH) binary mixture ratios in an electrospining atmosphere with various relative humidity (RH) levels. Scanning electron microscope micrographs showed that DMF/tetrahydrofuran and DMF/EtOH ratio and RH value could considerably affect the diameter, surface, and interior morphology of the resultant nanofibers. The nanofiber morphology was dependent upon the polymer/solvent(s)/water ternary phase diagram behavior. In overall, the partial hydrophilicity of styrene/acrylonitrile copolymer resulted in electrospun nanofibers with wrinkled surface. In addition, the incorporation of nonsolvent in the spinning solution and using high RH atmosphere forced the polymeric solution jet to intensively phase separate and, therefore, produce the nanofibers with highly interior porous structure during drying process. The maximal capacity and rate of oil sorption (170 g/g) was observed for the nanofibrous mat prepared using EtOH/DMF (2/3: vol/vol) and RH value of 60% showing the highest internal porosity. The results showed that the oil sorption capability and mechanical strength of the fibrous mat are strongly dependent on nanofibers diameter and porous structure, which can be controlled through adjusting the RH and spinning solvent quality. The electrospun mat with highest Young's modulus (7.68 MPa) was prepared using EtOH/DMF (2/3) binary mixture and RH value of 45%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45586.     

Preparation of poly(ether sulfone) nanofibers by gas‐jet/electrospinning

Poly(ether sulfone) (PES) nanofibers were prepared by the gas‐jet/electrospinning of its solutions in N,N‐dimethylformamide (DMF). The gas used in this gas‐jet/electrospinning process was nitrogen. The morphology of the PES nanofibers was investigated with scanning electron microscopy. The process parameters studied in this work included the concentration of the polymer solution, the applied voltage, the tip–collector distance (TCD), the inner diameter of the needle, and the gas flow rate. It was found from experimental results that the average diameter of the electrospun PES fibers depended strongly on these process parameters. A decrease in the polymer concentration in the spinning solutions resulted in the formation of nanofibers with a smaller diameter. The use of an 18 wt % polymer solution yielded PES nanofibers with an average diameter of about 80 nm. However, a morphology of mixed bead fibers was formed when the concentration of PES in DMF was below 20 wt % during gas‐jet/electrospinning. Uniform PES nanofibers with an average diameter of about 200 nm were prepared by this electrospinning with the following optimal process parameters: the concentration of PES in DMF was 25 wt %, the applied voltage was 28.8 kV, the gas flow was 10.0 L/min, the inner diameter of the needle was 0.24 mm, the TCD was 20 cm, and the flow rate was 6.0 mL/h. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Control of structure and morphology of highly aligned PLLA ultrafine fibers via linear-jet electrospinning

In this work, poly(l-lactic acid) (PLLA) ultrafine fibers with different morphology and structure were fabricated by a novel linear-jet electrospinning method which relies on a conventional electrospinning set-up with continuous rotating drum. To control the morphology and structure of PLLA electrospun fibers, different solution systems and electrospinning conditions were investigated. Two PLLA solution systems (PLLA/DMF/CH₂Cl₂ and PLLA/CH₂Cl₂) with different concentration and conductivity were used for the electrospinning and their influences on the formation of the linear electrospinning jet were discussed. Two types of collecting patterns with aligned buckling and linear structure were achieved under the linear electrospinning jet. Highly aligned PLLA electrospun fibers with porous surface could be formed by using the highly volatile solvent CH₂Cl₂. Here, it should be emphasized that the diameter and surface porosity of such highly aligned PLLA electrospun fibers can be fine tuned by varying the winding velocity. The results of SEM images and polarized FTIR investigations verified that the as-spun PLLA porous surface fibers were highly aligned and molecularly oriented, leading to the enhanced mechanical performance as compared to the non-woven PLLA electrospun fibers.     

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.     

Synthesis of ultrafine poly(styrene‐maleic anhydride) and polystyrene fibers by electrospinning

Fiber formation from atactic polystyrene (aPS) and alternating poly(styrene‐maleic anhydride) (PSMA) synthesized by free radical polymerization (AIBN, 90°C, 4 h) were investigated by electrospinning from various solutions. aPS was soluble in dimethylformamide (DMF), tetrahydrofuran (THF), toluene, styrene, and benzene, whereas PSMA was soluble in acetone, DMF, THF, dimethylsulfoxide (DMSO), ethyl acetate, and methanol. aPS fibers could be electrospun from 15 to 20% DMF and 20% THF solutions, but not from styrene nor toluene. PSMA, on the other hand, could be efficiently electrospun into fibers from DMF and DMSO at 20 and 25%, respectively. Few PSMA fibers were, however, produced from acetone, THF, or ethyl acetate solutions. Results showed that solvent properties and polymer–solvent miscibility strongly influenced the fiber formation from electrospinning. The addition of solvents, such as THF, generally improved the fiber uniformity and reduced fiber sizes for both polymers. The nonsolvents, however, had opposing effects on the two polymers, i.e., significantly reducing PSMA fiber diameters to 200 to 300 nm, creating larger and irregularly shaped aPS fibers. The ability to incorporate the styrene monomer and divinylbenzene crosslinker in aPS fibers as well as to hydrolyze PSMA fibers with diluted NaOH solutions demonstrated potential for post‐electrospinning reactions and modification of these ultrafine fibers for reactive support materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The change of bead morphology formed on electrospun polystyrene fibers

Polystyrene (PS) dissolved in the mixture of tetrahydrofuran (THF) and N,N-dimethyl formamide (DMF) was electrospun to prepare fibers of sub-micron in diameters. Electropinning parameters such as polymer concentration, applied voltage and tip-to-collector distance were controlled. From these parameters it was determined that while the surface tension of polymer solution had linear correlation with the critical voltage, throughput was dependent on electric conductivity. The electrospun PS fibers produced contained irregular beads and electrospinning certainly was enhanced with increasing DMF content. The bead concentration was also controlled by DMF content. The aspect ratio of the formed beads and the diameter of fibers were increased with increasing solution concentration. When PS was dissolved in only THF, an unexpected half hollow spheres (HHS) structure appeared. Also, different shape forms of PS non-woven mats have been prepared by controlling electrospinning parameters.     

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.     

Electrospinning of nanofibers from non-polymeric systems: polymer-free nanofibers from cyclodextrin derivatives

High molecular weight polymers and high polymer concentrations are desirable for the electrospinning of nanofibers since polymer chain entanglements and overlapping are important for uniform fiber formation. Hence, the electrospinning of nanofibers from non-polymeric systems such as cyclodextrins (CDs) is quite a challenge since CDs are cyclic oligosaccharides. Nevertheless, in this study, we have successfully achieved the electrospinning of nanofibers from chemically modified CDs without using a carrier polymer matrix. Polymer-free nanofibers were electrospun from three different CD derivatives, hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD) in three different solvent systems, water, dimethylformamide (DMF) and dimethylacetamide (DMAc). We observed that the electrospinning of these CDs is quite similar to polymeric systems in which the solvent type, the solution concentration and the solution conductivity are some of the key factors for obtaining uniform nanofibers. Dynamic light scattering (DLS) measurements indicated that the presence of considerable CD aggregates and the very high solution viscosity were playing a key role for attaining nanofibers from CD derivatives without the use of any polymeric carrier. The electrospinning of CD solutions containing urea yielded no fibers but only beads or splashes since urea caused a notable destruction of the self-associated CD aggregates in their concentrated solutions. The structural, thermal and mechanical characteristics of the CD nanofibers were also investigated. Although the CD derivatives are amorphous small molecules, interestingly, we observed that these electrospun CD nanofibers/nanowebs have shown some mechanical integrity by which they can be easily handled and folded as a free standing material.     

Characterization and application of electrospun alumina nanofibers

Alumina nanofibers were prepared by a technique that combined the sol–gel and electrospinning methods. The solution to be electrospun was prepared by mixing aluminum isopropoxide (AIP) in ethanol, which was then refluxed in the presence of an acid catalyst and polyvinylpyrolidone (PVP) in ethanol. The characterization results showed that alumina nanofibers with diameters in the range of 102 to 378 nm were successfully prepared. On the basis of the results of the XRD and FT-IR, the alumina nanofibers calcined at 1,100°C were identified as comprising the α-alumina phase, and a series of phase transitions such as boehmite → γ-alumina → α-alumina were observed from 500°C to 1,200°C. The pore size of the obtained γ-alumina nanofibers is approximately 8 nm, and it means that they are mesoporous materials. The kinetic study demonstrated that MO adsorption on alumina nanofibers can be seen that the pseudo-second-order kinetic model fits better than the pseudo-first-order kinetic model.     

Effects of processing parameters on morphology of electrospun polystyrene nanofibers

This study focused on the preparation of electrospun polystyrene (PS) nanofibers. PS solutions were prepared in single (dimethylformamide; DMF, dimethylacetamide; DMAc or tetrahydrofuran; THF) and mixed solvent (DMF/THF and DMAc/THF) systems with and without tetrabutylammonium bromide (TBAB) salt. The effects of PS concentration, solvent system, the addition of salt, appearance and diameter of PS fibers were examined. The average diameter of the as-spun fibers increased upon increasing PS concentration. The morphology of the fibers significantly depended on the properties of the solvents. The obtained fibers were smooth without any beads and their diameters were affected by the amount of THF in the solvent and PS concentration. The beads in the fibers disappeared and the fiber diameter significantly decreased after the addition of TBAB. The smallest diameter and the narrowest diameter distribution of PS nanofibers (376±36 nm) were obtained from 15% PS solution in DMAc with 0.025% w/v TBAB.     

Electrochemical properties of polypyrrole/sulfonted SEBS composite nanofibers prepared by electrospinning

The electrochemical behavior of electrospun polypyrrole (PPy)/sulfonated-poly(styrene-ethylene-butylenes-styrene) (S-SEBS) composite nanofibers was investigated, compared to PPy/poly(styrene-ethylene-butylenes-styrene) (SEBS) fibers prepared by a casting method. The electrospun PPy/S-SEBS (E-PSS) fibers were about 300 nm in average diameter, while PPy/SEBS composite (C-PS) prepared by a casting method showed the granular macroporous structure. The effect by both electrospinning and sulfonation results in higher electrochemical capacity due to the increase of doping level, high electrical conductivity, low interfacial resistance, and high reversibility by easy intercalation of Li ion. In addition, sulfonated SEBS induces higher elongation force to jet in the processing of electrospinning due to the role of dopant.     

Electrostatic polymer processing of isotactic poly(4-methyl-1-pentene) fibrous membrane

Isotactic poly(4-methyl-1-pentene) (P4M1P) is a widely used polymer in industrial applications and specifically, in medical products. Producing micro- or nanofibers would expand the usefulness of P4M1P to a broad range of medical applications. The choice and quality of solvent for the solution used for electrospinning can have a dramatic effect on the spinnability of fibers and on their morphological appearance. In this study, four solvent systems: cyclohexane, cyclohexane/acetone mixture, cyclohexane/dimethyl formamide (DMF) mixture and cyclohexane/acetone/DMF mixture have been investigated. As demonstrated by FE-SEM, electrospun fibers with different morphologies including round, twisted with a roughened texture, curled and twisted-ribbon shapes were formed. The fiber shape and morphology depended strongly on the type and amount of non-solvent used.     

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     

溶剂及溶液中无机盐对电纺纤维的影响

采用二甲基乙酰胺(DMAc)与丙酮的混合溶剂,对醋酸纤维素(SCA)电纺过程中溶液性质对纤维直径及形态的影响进行研究。不同的溶液性质具体表现为不同的溶度参数、黏度、表面张力、挥发度等,而纤维直径的细化是以上参数共同作用的结果。而本文中,由于丙酮对溶液的挥发度起了决定性作用,使电纺纤维的直径的改变受其影响最大。当DMAc∶丙酮的混合比为20∶80时,纤维表面会充满凹陷的小孔。另外,无机盐的加入也会导致溶液黏度、表面张力呈先下降后上升的趋势,电导率和电荷密度随之上升。在其他条件一定时,SCA/LiCl体系的纤维直径要小于SCA/CaCl2体系;无机盐含量超过2%时,纤维直径会有一定程度的增加。     

Molecular orientation and mechanical property size effects in electrospun polyacrylonitrile nanofibers

Electrospinning of polymeric solutions entails high jet velocities which could orient the polymer molecules along the jet direction. Polarized Fourier Transform IR spectroscopy (FTIR), Wide angle X-ray diffraction (WAXD) and Microelectromechanical System (MEMS)-based single nanofiber mechanical property experiments were employed to investigate the molecular orientation and crystallinity in electrospun polyacrylonitrile (PAN) nanofibers produced under different electrospinning conditions with diameters mainly varying between 100 and 300 nm. FTIR measurements with nanofibers fabricated at three different electrospinning distances, but under the same electric field intensity, revealed an enhanced molecular orientation only for the longest electrospinning distance. At long electrospinning distances the fiber solvent content is substantially reduced resulting in high viscosity, and, therefore, sustained shear stresses, which, in turn, allows for permanent molecular orientation. The orientation factors from polarized FTIR were in good agreement with the mechanical property trends obtained from individual nanofibers, where high elastic moduli and yield strengths were recorded from nanofibers with diameters smaller than 300 nm, which were fabricated at the longest electrospinning distance. WAXD studies on bundles of aligned PAN nanofibers showed small crystallinity which did not follow the trends in the mechanical properties and varied rather non-monotonically from 7%, for fibers spun at the shortest distance, to 17% for fibers spun at the longest distance used in this study.     

Studies on the synthesis of electrospun PAN‐Ag composite nanofibers for antibacterial application

We have successfully synthesized polyacrylonitrile (PAN) nanofibers impregnated with Ag nanoparticles by electrospinning method at room temperature. Briefly, the PAN‐Ag composite nanofibers were prepared by electrospinning PAN (10% w/v) in dimethyl formamide (DMF) solvent containing silver nitrate (AgNO₃) in the amounts of 8% by weight of PAN. The silver ions were reduced into silver particles in three different methods i.e., by refluxing the solution before electrospinning, treating with sodium borohydride (NaBH₄), as reducing agent, and heating the prepared composite nanofibers at 160°C. The prepared PAN nanofibers functionalized with Ag nanoparticles were characterized by field emission scanning electron microscopy (FESEM), SEM elemental detection X‐ray analysis (SEM‐EDAX), transmission electron microscopy (TEM), and ultraviolet‐visible spectroscopy (UV‐VIS) analytical techniques. UV‐VIS spectra analysis showed distinct absorption band at 410 nm, suggesting the formation of Ag nanoparticles. TEM micrographs confirmed homogeneous dispersion of Ag nanoparticles on the surface of PAN nanofibers, and particle diameter was found to be 5–15 nm. It was found that all the three electrospun PAN‐Ag composite nanofibers showed strong antibacterial activity toward both gram positive and gram negative bacteria. However, the antibacterial activity of PAN‐Ag composite nanofibers membrane prepared by refluxed method was most prominent against S. aureus bacteria. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012