Electrospun nanofibers from a multihole spinneret with uniform electric field

This study presents a multihole spinneret with a metal flat electrode to obtain uniform electric field and meet a high production requirement. We demonstrate that the multihole spinneret produces finer fiber diameters and more concentrated fiber mat compared to the conventional multineedle electrospinnig system. This study focuses on the effect of the electric field distribution on the spinning process and the resultant nanofibers. The three‐dimensional electric field simulation results show that the multihole spinneret creates not only a more uniform electric field, but also a stronger electric field except for the area very close to the spinneret. The measurement of the electric field verifies the simulation results. This study shows that fine fibers, as well as concentrated and thick fiber mat can be obtained by this multihole electrospinning system at a high production rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3221–3228, 2013     

Polyurethane fibrous membranes tailored by rotary jet spinning for tissue engineering applications

Polymeric membranes have gained popularity as fibrous structures for tissue regeneration. This research focuses on the rotary jet spinning (RJS) process combined with a polymer as a strategy for designing membranes. To this end, RJS-polyurethane (RJS-PU) membranes with different microstructures were produced. Considering the effects of solution properties on fiber production, the viscosity of PU solutions was evaluated. Membrane morphology was studied based on scanning electron microscopy and 2D fast Fourier transform analysis. The chemical and thermal properties were characterized by Fourier-transform infrared spectroscopy and thermogravimetric analysis, respectively. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and Live/Dead cell assays were performed to determine the material cytotoxicity by assessment of the profile of proliferation and cell viability. The results indicated that the combination of PU and RJS was an effective one for the production of fibrous structures for tissue engineering applications, demonstrating good compatibility with the cultured osteoblastic cell line. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48455.     

Effect of the flow conditions of the spinning solution through the spinneret on the spinning of nitron fibre

Conclusions At various flow rates of spinning solution, breakage of the freshly spun yarn in the precipitation bath takes place at the very same value of true jet stretch, which does not depend on the diameter of the spinneret holes.The rate of take-up of the spun yarn from the precipitation bath or from the steam chamber exerts an effect on the uniformity of the fibre obtained.The limiting rates of yarn take-up from the precipitation bath and from the steam chamber have been found from carrying out a process of defect-free spinning of Nitron fibre.Translated from Khimicheskie Volokna, No. 3, pp. 24–26, May–June, 1983.     

异形喷丝孔壁面条件对纺丝液流动过程的影响

基于广义Navier模型建立了三叶形喷丝孔的全三维模型,用于分析异形喷丝孔内壁粗糙程度对纺丝液流动过程的影响,并对聚酰胺酸/二甲基乙酰胺(PAA/DMAC)体系纺丝液在异形喷丝孔内的粘弹性流动过程进行了模拟,分析了不同壁面滑移系数(Ks)条件下纺丝液的流动状态和速度分布。结果表明:减少壁面粗糙度,Ks减小,纺丝液在喷丝孔内流动的径向速度分布更趋均匀,但沿长轴和短轴方向的径向速度分布变化并不完全一致;纺丝液沿喷丝孔轴向的最大速度随Ks减小相应降低,Ks为1×108和1×105时,最高轴向速度分别为17.4,9.0 m/s。     

Recent development of centrifugal electrospinning

As a high‐output nanoscale fiber production method, centrifugal electrospinning (CES) has attracted increasing attention, and this has fostered its quick development. In this article, we review this technique and summarize its mechanism, characteristics, classification, and process equipment. Furthermore, we classify the effects of several CES process parameters on the fiber properties into three different categories. The mechanisms of these effects on the fiber characteristics are analyzed. Finally, the CES issues are summarized, and some strategic solutions and prospects are proposed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44578.     

Influence of additive on structure of PVDF nanofibers electrospun via new spinneret design

Surface morphology and internal structure of polyvinylidene fluoride (PVDF) nanofibers were investigated in this study. PVDF nanofibers were electrospun by two types of spinnerets, nozzle and channel spinneret, with different contents of tetrabutylammonium chloride (TBAC) and at various take‐up velocities. The new spinneret design, channel spinneret, resulted in thicker fibers while high β‐phase content and small d‐spacing were obtained, especially in the case of low TBAC content. And high TBAC content led to finer PVDF nanofibers with high β‐phase content and small d‐spacing compared to low TBAC content regardless of spinneret types, while an increase in take‐up velocity did not have significant effect on both morphology and internal structure of PVDF nanofibers regardless of TBAC content. It suggests that electrostatic drawing acted dominantly rather than mechanically drawing in the system cooperating TBAC. However, the decreasing difference between two types of spinnerets was observed in terms of β‐phase content with an increase in TBAC content. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1752–1758, 2013     

环隙式离心萃取器流场研究进展

围绕工业应用,人们在环隙流场稳定性、水力学特性等方面做了大量研究,而对环隙的流场流动机理、泰勒涡流场结构等方面的研究较少,随着线性和非线性理论、计算流体力学和流动可视化技术的飞速发展,对环隙流场流动机理、涡流场的结构进行详细直观描述有了可能,主要从环隙流场可视化、环隙流场数值模拟2个方面对该研究进行了系统的分析总结,并为将来的研究工作提出了几点意见。     

Formation of melt and solution spun polycaprolactone fibers by centrifugal spinning

Nano‐ and microfibers have a myriad of applications ranging from filtration, composites, energy harvesting, to tissue engineering and drug delivery. Electrospinning, the most common method to produce such fibers, has many limitations including low fiber output and solvent dependency. Centrifugal spinning is a new technique that uses centrifugal forces to form nano‐ and microfibers both from solution and the melt. In this work, the effect of melt temperature, collector distance, rotation speed, and concentration (for polymer solutions) of polycaprolactone were evaluated with respect to fiber morphology, diameter, alignment, and crystallinity. The fiber diameter generally decreased with increasing rotation speed and reduced concentration. Crystallinity for spun fibers decreased compared to the bulk polymer. Fiber alignment was improved with rotation speed for the melt‐spun fibers. The fiber mats were evaluated as tissue scaffolds with neuronal PC12 cells. The cells adhered and extended neurites along the fibers for both melt and solution‐spun scaffolds. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41269.     

聚酯熔体在喷丝孔中剪切流动对纺丝动力学的影响

通过建立动力学模型,采用有限元的方法研究了喷丝孔结构对涤纶熔纺动力学的影响;通过改变喷丝孔微孔直径、增加微孔出口倒角,计算得到了喷丝孔内熔体的挤出速度和压力分布,以及纺程段丝条的速度、速度梯度、直径、温度、拉伸应力、取向和结晶分布;进一步讨论了微孔直径和微孔出口倒角对于喷丝孔内熔体的流动行为、压力降、挤出胀大以及纺程段丝条的结构性能的影响。结果表明:改变喷丝孔微孔直径能够有效地调控喷丝孔内熔体的挤出速度和压力降,从而改变挤出胀大比和拉伸应力;微孔出口倒角对喷丝孔内熔体流动影响不大,主要影响纺程段丝条的结构与性能;喷丝孔微孔带有出口倒角时,可以削弱纺丝过程的挤出胀大现象,纺程段丝条的拉伸应力、取向度和结晶度都有不同程度的提高,并且会使发生取向和结晶的位置更加靠近喷丝板。     

Antimicrobial activity of tellurium‐loaded polymeric fiber meshes

A series of poly(methyl methacrylate) solutions loaded with varying concentrations of tellurium particles are prepared and processed into continuous and smooth microfiber meshes. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy are used to study the morphology and surface elemental composition of the composite fibers. Fiber diameters range between 7 and 14 µm with surface nanopores on the fibers ranging between 100 and 200 nm. Energy‐dispersive X‐ray spectroscopy confirmed successful incorporation of tellurium particles into the fibers. The concentration of tellurium in the composite significantly influenced fiber diameter, pore size, and morphology. The antibacterial activity of the prepared fibers is tested using Escherichia coli K12. The fibers are incubated in bacterial suspensions for 24 h at 37 °C and 150 rpm. Antibacterial activity is assessed through the colony‐counting method and is found to be dose dependent. The fibers with 4 wt % tellurium exhibited the most potent antibacterial properties as a 1.16 log reduction was observed. © 2018 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46368.     

Stability and spinnability of modified melamine–formaldehyde resin solution for centrifugal spinning

Melamine microfibers were first prepared by centrifugal spinning. The stability and spinnability of a melamine–formaldehyde (MF) resin solution were improved as expected by adding various modifier combinations. Considering the storage stability of solutions characterized by visual inspection, turbidity tests, and viscosity measurements and combined with the fiber morphology, the optimal modifier combination was obtained. The spun fibers manifested a good morphology and thermal stability as measured by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Moreover, microfibers prepared by three spinning methods (centrifugal spinning, electrospinning, and centrifugal electrostatic spinning) were compared to choose the suitable spinning method for different fields in the future. This work provides systematic and scientific guidance on the synthesis of MF resin solutions and rapid mass production of melamine microfibers and also demonstrates that centrifugal spinning of melamine microfiber is a promising candidate for flame retardance and CO₂ adsorption at elevated temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46072.     

Thermal response of an electric heating rapid heat cycle molding mold and its effect on surface appearance and tensile strength of the molded part

Rapid heat cycle molding (RHCM) is a newly developed injection molding technology in recent years. In this article, a new electric heating RHCM mold is developed for rapid heating and cooling of the cavity surface. A data acquisition system is constructed to evaluate thermal response of the cavity surfaces of the electric heating RHCM mold. Thermal cycling experiments are implemented to investigate cavity surface temperature responses with different heating time and cooling time. According to the experimental results, a mathematical model is developed by regression analysis to predict the highest temperature and the lowest temperature of the cavity surface during thermal cycling of the electric heating RHCM mold. The verification experiments show that the proposed model is very effective for accurate control of the cavity surface temperature. For a more comprehensive analysis of the thermal response and temperature distribution of the cavity surfaces, the numerical‐method‐based finite element analysis (FEA) is used to simulate thermal response of the electric heating RHCM mold during thermal cycling process. The simulated cavity surface temperature response shows a good agreement with the experimental results. Based on simulations, the influence of the power density of the cartridge heaters and the temperature of the cooling water on thermal response of the cavity surface is obtained. Finally, the effect of RHCM process on surface appearance and tensile strength of the part is studied. The results show that the high‐cavity surface temperature during filling stage in RHCM can significantly improve the surface appearance by greatly improving the surface gloss and completely eliminating the weld line and jetting mark. RHCM process can also eliminate the exposing fibers on the part surface for the fiber‐reinforced plastics. For the high‐gloss acrylonitrile butadiene styrene/polymethyl methacrylate (ABS/PMMA) alloy, RHCM process reduces the tensile strength of the part either with or without weld mark. For the fiber‐reinforced plastics of polypropylene (PP) + 20% glass fiber, RHCM process reduces the tensile strength of the part without weld mark but slightly increases the tensile strength of the part with weld mark. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Application of response surface methodology to evaluate the effect of dry‐spinning parameters on poly (ε‐caprolactone) fiber properties

Poly (ε‐caprolactone) fibers were prepared by dry‐spinning method. The effect of processing parameters on linear density, mechanical, and morphological properties of fibers was investigated using the response surface methodology (RSM). This method allowed evaluating a quantitative relationship between polymer concentrations, spinning speed, and draw ratio on the properties of the fibers. Polynomial regression model was fitted to the experimental data to generate predicted response. The results were subjected to analysis of variance to determine significant parameters. It was found that all three parameters had significant effect on linear density of fibers. Combined effect of concentration and spinning speed was observed in which the linear density of fiber was more sensitive to changes in the solution concentration at lower spinning speed. Polymer concentration had the largest influence on the mechanical properties of fibers. An average cross‐sectional radius of fibers was affected by concentration and draw ratio in opposite manner. Among all three parameters, only polymer concentration had significant effect on circularity of fiber cross sections. By applying the RSM, it was possible to obtain a mathematical model that can be used to better define processing parameters to fabricate dry‐spun PCL fiber in a more rational manner. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42113.     

Cylindrical-electrode-assisted solution blowing for nanofiber spinning

In this article, a novel process called cylindrical-electrode-assisted solution blowing spinning (CSBS) for producing excellent quality nanofibers with simultaneous electrostatic force and air stretching is reported. The originality of this work is in a new apparatus. With a cylindrical electrode, the solution jets were noncontact charged because of electrostatic induction; this is different from traditional solution-blowing spinning (SBS). Poly(ethylene oxide) nanofibers were fabricated by the CSBS technique for the first time. The scanning electron microscopy results prove that the nanofiber mats produced by CSBS and formed by individual cylindrical-shaped fibers presented a more regular morphology than SBS ones. Compared with that of SBS fibers, the CSBS fiber diameter standard deviation decreased by 21%, and the mean diameter decreased by 6.17%. Their thinner and more uniform fibers may make CSBS fiber webs a better candidate for filtration and other uses compared with SBS ones. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47087.     

Predicting poly(vinyl pyrrolidone)'s solubility parameter and systematic investigation of the parameters of electrospinning with response surface methodology

The solubility parameters were used to choose the solvent for poly(vinyl pyrrolidone) (PVP) in electrospinning. In this study, a novel method for predicting the contribution value of the pyrrolidone group (a typical part of the PVP molecular structure) was proposed. The solubility parameters of PVP were calculated by this method, and accordingly, ethanol was chosen as the solvent for PVP. What is more, response surface methodology was used to facilitate a systematic investigation on the influence of the PVP solution concentration, feed rate, distance between the tip and collector, and operating voltage on the fiber diameter and morphology in electrospinning. The predicted fiber diameters by the response regression model, and the experimental values were in close proximity. The solution concentration and feed rate both had significant effects on the PVP fiber diameter, and there was some interaction between the solution concentration and the feed rate in this system. In addition, this study provided a train of thought for the electrospinning of polymer fibers with controllable and predictable fiber diameters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40304.     

Numerical investigation of spinneret geometric effect on spinning dynamics of dry‐jet wet‐spinning of cellulose/[BMIM]Cl solution

In this study, the effect of spinneret geometry, including the entrance angle α of the entrance channel, the length L_s, and the diameter D₀ of the exit channel, on the spinning dynamics of dry‐jet wet‐spinning of cellulose/1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) solution was simulated by using finite element method. Based on the mathematical model of dry‐jet wet‐spinning established in our previous work (Xia et al., Cellulose 2015, 22, 1963) the radial and axial profiles of velocity, pressure, and shear rate in the spinneret and the profiles of diameter, temperature, and tensile stress in the air‐gap region were obtained. From the simulated profiles, the effect of spinneret geometric parameters on the flow behavior and the pressure drop of polymer solution in the spinneret and the die‐swell ratio near the spinneret was discussed. The entrance angle α of the entrance channel mainly influences the flow behavior of polymer solution in the spinneret and the die‐swell effect near the spinneret. As the decrease of the entrance angle α of the entrance channel, the vortices in the spinneret could be removed and the die‐swell ratio decreases. The increase of the length L_s of the exit channel results in the increase of pressure drop in the spinneret and the decrease of the die‐swell ratio. It is also found that the increase of the diameter D₀ of the exit channel reduces the flow velocity of polymer solution and decreases the pressure drop in the spinneret at a constant mass flow rate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43962.     

干喷湿法PAN原丝喷头稳定性探讨

分别从喷头原液均一性、喷丝板及其内部组件、空气层高度、凝固浴液面波动等角度出发,探讨了不同原因对干喷湿法PAN原丝喷头稳定性的影响。指出干喷湿法喷头的稳定对PAN原丝生产线的稳定性起着决定性意义。