Spinneret Diameter Research Articles

Mechanical Properties of PVA/Alginate Membranes Fabricated using Electrospinning as A Wound Dressing

Alginate is an interesting natural biopolymer due to its many benefits and good biological properties. Observing the mechanical properties of PVA/Alginate fibers made by electrospinning machines can help predict their behavior and measure their performance under various conditions including applied external forces. Therefore, this study investigated the elastic properties of PVA/Alginate membranes, specifically tensile strength and elongation. The fabrication material used is PVA / Alginate solution with a PVA solution concentration of 20% and alginate solution 2.5%. The electrospinning process is carried out by optimizing at a voltage of 25 kV, the distance between the spinneret end and the collector is 15 cm, the flow rate is 130, and the spinneret diameter variations are 0.4 mm, 0.6 mm, and 0.8 mm. To determine the morphology of the fiber surface, observations were made using ocular microscopes and SEM. From this observation, it is known that the morphology formed using a 0.4 mm spinneret has the tightest structure among the three sizes of spinneret diameter. To determine the effect of spinneret diameter on the value of tensile strength and elongation, tensile strength tests are carried out. The tensile strength and elongation values of the membrane obtained with variations in spinneret diameters of 0.4 mm, 0.6 mm, and 0.8 mm are 1.96 MPa, 3.77 MPa and 6.11 MPa respectively and the elongation values are 17%, 52.7%, and 97%. With medical material standards, it has a tensile strength value between 1 MPa – 24 MPa and an elongation value between 17% – 207%, so that PVA / Alginate fiber membranes have the potential to be applied as wound dressings.

Continuous Nanofiber Bundle Production Using Helical Spinnerets with Different Configurations in Needleless Electrospinning

This study investigates the production of continuous nanofiber bundles using needleless electrospinning with a focus on helical spinneret configurations. It delves into the effects of spinneret diameter, pitch length, and thickness on nanofiber bundle characteristics, employing polyacrylonitrile as the polymer. The research highlights the significant impact of these parameters on the nanofiber morphology, bundle width, productivity, and deposition properties of nanofiber bundles. Scanning electron microscopy imaging, bundle depositions analyses, and electric field modeling with COMSOL Multiphysics are applied for the nanofiber bundles electrospun by helical spinnerets. As the diameter of the spinneret increases, productivity, bundle width, deposition ratio, deposition intensity, and deposition homogeneity are increased significantly. Additionally, an increase in spinneret thickness leads to a decrease in average nanofiber diameter. Specifically, increasing the spinneret diameter from 30 to 50 mm, pitch length from 20 to 40 mm, and reducing thickness from 3 to 1 mm increases productivity by 170%, 72%, and 32%, respectively. As a result of practical and modeling studies on helical spinnerets, the optimized parameters are determined as 1 mm thickness, 40 mm pitch length, and 50 mm diameter.

Electrospun nanofibrous polyether-block-amide membrane containing silica nanoparticles for water desalination by vacuum membrane distillation

In this work, hydrophobic nanofibrous membranes based on polyether-block-amide (PEBAX-2533) were prepared by the electrospinning technique for using in the vacuum membrane distillation (VMD) process for water desalination applications. In the first part of this study, the influence of the electrospinning conditions like polymer concentration, surfactant concentration, applied voltage, spinneret to collector distance, feed injection rate and spinneret diameter on the morphology of the electrospun mats was investigated and optimized to obtain uniform, bead-less and defect-free nanofibrous PEBA membranes. In the second part, the electrospun nanofibrous SiO2/PEBAX-2533 membranes were fabricated by incorporating silica nanoparticles into the polymer solution. The morphology, structure, and surface properties of the prepared nanofibrous SiO2/PEBA membranes were characterized by the SEM, FTIR, OCA, and tensile strength tests. Likewise, the VMD performance of the prepared electrospun SiO2/PEBA membranes was studied for the desalination of NaCl aqueous solutions at various operating conditions. It was observed that the VMD performance of the prepared electrospun nanofibrous SiO2/PEBAX-2533 membrane containing 8 wt% of silica nanoparticles had the best separation performance in terms of the water flux, flux decline and TDS content of the permeate stream. Finally, a comparison between the prepared nanofibrous SiO2/PEBAX-2533 membrane and a commercial PVDF membrane revealed that the VMD separation performance and long-term stability of the electrospun membrane were much better than those of the commercial PVDF membrane.

Controlling Topography and Crystallinity of Melt Electrowritten Poly(ɛ-Caprolactone) Fibers.

Melt electrowriting (MEW) is an aspiring 3D printing technology with an unprecedented resolution among fiber-based printing technologies. It offers the ability to direct-write predefined designs utilizing a jet of molten polymer to fabricate constructs composed of fibers with diameters of only a few micrometers. These dimensions enable unique construct properties. Poly(ɛ-caprolactone) (PCL), a semicrystalline polymer mainly used for biomedical and life science applications, is the most prominent material for MEW and exhibits excellent printing properties. Despite the wealth of melt electrowritten constructs that have been fabricated by MEW, a detailed investigation, especially regarding fiber analysis on a macro- and microlevel is still lacking. Hence, this study systematically examines the influence of process parameters such as spinneret diameter, feeding pressure, and collector velocity on the diameter and particularly the topography of PCL fibers and sheds light on how these parameters affect the mechanical properties and crystallinity. A correlation between the mechanical properties, crystallite size, and roughness of the deposited fiber, depending on the collector velocity and applied feeding pressure, is revealed. These findings are used to print constructs composed of fibers with different microtopography without affecting the fiber diameter and thus the macroscopic assembly of the printed constructs.

Preparation and Characterization of Poly(lactic acid) Micro- and Nanofibers Fabricated by Centrifugal Spinning

In this paper, poly(lactic acid) (PLA) micro- and nanofibers were successfully prepared by centrifugal spinning which is a more simple and effective approach to produce micro/nanofibers. The morphology of fibers was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), while their thermal properties by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The results showed that the diameter of PLA fibers increased significantly with increasing solution concentration and decreased slightly with increasing collection distance. It can be controlled below 500 nm at the optimal process parameters which were found to be spinning solution concentration of 6 %, spinneret diameter of 0.11 mm, rotational speed of 5500 rpm and collecting distance of 15 cm. Although the crystallinity of the PLA fibers was weaker than that of the PLA pellets due to the insufficient adjustment of the molecular chain in rapid solvent evaporation and short stretching time, it can be improved by increasing the rotational speed from 4500 to 7000 rpm. The glass transition temperature (Tg) and melting temperature (Tm) of the fibers were nearly keeping constant compared to the PLA pellets. Its good degradability was demonstrated by the loss of fibers structure completely within 5 hours of immersion in NaOH at pH 13.

Simulation of Jet Motion during Electrospinning Process through Coupled Multiphysics Method

A multiphysics model, used for predicting jet velocity by solving incompressible Navier-Stokes equations coupled with electric volume force, has been developed to simulate the three-dimensional polymer jet produced during electrospinning process. By varying the parameter values in the model, the effects of parameters, including flow rate and viscosity of polymer solution, spinneret diameter, and applied voltage on jet velocity are discussed. This model is validated by comparing with experimental results.

Characterization of the Properties of Electrospun Blended Hybrid Poly(Vinyl Alcohol)_Aloe Vera/Chitosan Nano-Emulsion Nanofibrous Membranes

The spinning solution of blended hybrid poly (vinyl alcohol) (PVA)_Aloe Vera (AV) with various concentrations (0%, 3%, 10% and 15%) of chitosan nanoemulsion (CSNe) were electrospun under optimized conditions of high DC voltage 15 kV, distance of spinneret tip to collector plate 16.5 mm and spinneret diameter 0.8 mm. This work aims to manufacture the blended hybrid PVA_AV/CSNe nanofibrous membranes and characterize the solution and fiber properties, and tensile properties of the nanofibrous membranes by varying CSNe concentrations. Scanning electron microscopy (SEM) results revealed that beads-free fiber structure featured in all electrospun membranes with relatively homogeneous fiber size distribution. An increase of CSNe concentration from 0% to 15% reduces the average fiber size from 366 nm to 180 nm and increase tensile strength from 2,52  0.54 MPa to 6.18  0.15 MPa and tensile modulus from 7.5  1.06 MPa to 21.9  9.88 MPa of the membranes, respectively. The tensile strength of the present blended hybrid PVA_AV/CSNE nanofibrous membranes with 15% CSNe concentration and tensile modulus of that with all CSNe concentrations are included in the range of the natural skin properties: i.e. (5.00 – 30.00 MPa) and (4.6 – 20.0 MPa) for tensile strength and modulus, respectively. Such data suggest the potential use of the membranes as wound dressing material in the near future.

The effect of process parameters on the electrospun polystyrene fibers

Electrospinning is one of the methods for obtaining nano/microfibers, using polymeric solutions. These nanofibrous membranes are highly porous with interconnected pores, having high specific surface area and small pore size, making them a suitable candidate for filtration applications. The properties of electrospun fibers are influenced by polymer solution, solvent, solution concentration, viscosity, electrical conductivity, electrical voltage, spinneret to collector distance etc. Expanded polystyrene is a polymeric product that is usually used for insulation and packaging. Recycling expanded polystyrene into nanofibers with applications in filtration could be useful from an economic point of view. The purpose of this study was to investigate the influence of expanded polystyrene polymer solution characteristics (concentration, viscosity) and the process parameters (applied voltage, distance between the tip and the collector plate, flow rate of the polymer solution) on the morphology and the properties of the obtained electrospun fibers. Therefore, three EPS solutions with 10, 15 and 20% wt. concentration were prepared and were electrospun under processing conditions with an applied voltage of 12, 15 and 18 kV, a spinneret-to-collector distance of 20 cm, a flow rate of solution of 1.5 and 2 mL/hour, a spinneret diameter of 0.8 mm and stationary copper substrate. The morphology of the electrospun fibers was observed by scanning electron microscopy. The mechanical properties were evaluated by tensile strength and elongation tests.

Recycled fiber from straw waste: effect of take-up speed and spinneret diameter to linear density and tenacity

Recycled fiber has a great potential as a solution to meet overgrowing synthetic fiber demand and reduce plastic waste in the same time. In the previous research, bottle cap waste is used as the material of the recycled fiber. The result shows that fiber tenacity of recyled fiber from bottle cap waste has low tenacity, different polymer. This phenomena may have been caused by the present of pigment molecule. This research focused on producing recycled fiber from straw waste which has low pigment content. Straw waste was washed and cleaned before the cutting process. Then, the waste was processed in the experiment melt spinning machine with plunger system and single hole orifice in various diameter, 4 mm, 10 mm and 15 mm. The processing temperature was 140° C temperature in three take-up speed, 3.00 m/minutes, 10.30 m/ minutes and 19.16 m/ minutes. The diameter and cross section shape of recycled polyethylene fiber were obtained by using electric microscope with software assistance. The linear density of the recycled fiber was analysed by calculating it with denier and the mechanical strength of the fiber was measured in accordance with the ASTM D 3379-75 standard. High take-up speed leads to higher linear density and take-up speed value is proportionally linear with the tenacity of fiber produced. Moreover, the spinneret diameter is proportionally linear with linear density but it is inversely linear with the tenacity of the fiber produced.

Optimization of rotating-jet electrospinning process using response surface methodology

Rotating-jet electrospinning method is one of the efficient techniques for producing aligned nanofibers. This paper reports an accurate investigation on the influence of collector diameter (CD), voltage, polymer concentration (PC), and insulator length (IL) of spinneret on the degree of fiber alignment (DFA), production rate of fiber, and fiber diameter. The polymer solution was a mixture of polyacrylonitrile and N,N-dimethylformamide. The ranges of independent variables were 20–50 cm for CD, 10–22 kV for voltage, 13–19 wt% for PC, and 0.5–3 cm for IL. To minimize the number of required experiments for a complete evaluation, response surface methodology (RSM) and central composite rotatable design were applied by means of Expert Design Software. After defining the upper and lower bounds of the above independent variables in the software, 30 unique experiments were delivered. The recommended operating conditions by the software were exactly applied in the laboratory and the corresponding values for the DFA, production rate, and fiber diameter were measured. The nanofiber morphology was examined by scanning electron microscopy (SEM). By applying the least-squares method in the DX7.0.0 software, well-fitting polynomial correlations to the experimental results were obtained, and using these correlations, the influence of independent variables and responses was comprehensively studied. Finally, the best values of independent variables for optimizing the responses were determined using RSM.

Preparation and characterization of hollow Fe2O3 ultra-fine fibers by centrifugal spinning

In this paper, the hollow Fe2O3 ultra-fine fibers were successfully prepared by the centrifugal spinning followed by the calcination process. Several spinning parameters including the concentration of FeCl3, rotational speed and diameter of spinneret were discussed for determination of optimum spinning condition. The resultant as-spun fibers and hollow Fe2O3 ultra-fine fibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), FT-IR spectra and X-ray photoelectron spectroscopy (XPS). The results showed that the diameters of the as-spun fibers and the hollow Fe2O3 ultra-fine fibers were 1.0–6.0μm and 0.5–5.0μm, respectively. The concentration of FeCl3 had an impact on as-spun fibers hardly, but on diameters of the hollow Fe2O3 ultra-fine fibers. The diameters of the as-spun fibers become smaller and the hollow Fe2O3 ultra-fine fibers become more fragile when the rotational speed increased or the inner diameter of the spinneret decreased.

Additive manufacturing of fibrous sub-micron poly(e-caprolactone) scaffolds for tissue engineering

Event Abstract Back to Event Additive manufacturing of fibrous sub-micron poly(ε-caprolactone) scaffolds for tissue engineering Gernot Hochleitner1, Tomasz Jüngst1, Toby D. Brown2, Kathrin Hahn1, Claus Moseke1, Franz Jakob3, Paul D. Dalton1 and Jürgen Groll1 1 University of Würzburg, Department for Functional Materials in Medicine and Dentistry, Germany 2 Queensland University of Technology, Institute of Health and Biomedical Innovation, Australia 3 University of Würzburg, Orthopedic Center for Musculoskeletal Research, Germany Introduction: The field of additive manufacturing (AM) has attracted increasing interest over the last decade, in part for tissue engineering (TE) approaches. In our study we use an emerging type of AM technology, termed Melt Electrospinning Writing (MEW), a process that combines the characteristic benefits of 3D printing and electrospinning. When using an electrohydrodynamic drawing process, thermoplastic melts can be deposited to well defined scaffold structures, even with sub-micron sized fiber diameters (817 ± 165 nm) as we recently observed[1],[2]. Materials and Methods: A custom-built device was used to manufacture scaffolds made of poly(ε-caprolactone) (PCL), a biodegradable polymer with a history of clinical use. In order to investigate the influence of the instrumental parameters, the feeding pressure (0.5–4.0 bar), heating temperature (80–120°C), acceleration voltage (2.0–10.0 kV), spinneret diameter (21 G; 23 G; 25 G; 27 G; 30 G; 33 G), collector distance (1–10 mm) and collector speed (1000–9000 mmmin-1) was systematically varied and optimized. To confirm cell adhesion to the scaffolds, we printed scaffolds directly onto hydrophilized (NCO-sP(EO-stat-PO)coated) glass slides and seeded primary human mesenchymal stromal cells (hMSC) to them afterwards[1]. Results and Discussion: Through the adjustment of instrumental parameters, PCL fibers with diameters ranging from 50 µm to the sub-micron level (817 ± 165 nm) can be deposited to highly uniform scaffolds (figure 1 A, B, C). Thus, MEW can be used to tailor scaffold architecture and to define its specific surface, which is of high interest for degradation or cell-interaction processes. Figure 1: A, B & C: MEW PCL scaffolds with a box structure consisting of 2x50 layers of sub-micron fliaments. D: HMSCs adhered to a scaffold after 4 days in vitro[1]. We observed excellent scaffold adhesion to the microscope slide that could withstand media changes and up to 2 weeks in vitro. The MSCs adhered well on the scaffolds, forming circular structures, even when the box spacing is only 90µm (figure 1 D). Further, the hydrophilic coatings of the glass slides not only prevented cell adhesion to the underlying surface, so that specific scaffold cell interactions could be observed[1]. Conclusion: While common AM methods, such as fused deposition modeling, allow a fabrication of fibers in a range of 100 µm microns and more, MEW can print sub-micron fibers with medical grade polymers. In contrast to solution electrospinning, drawing fibers from melts enables manufacturing without the use of often toxic solvents highly interesting for TE or medical approaches[1]. German Academic Exchange Service (DAAD, project No. 54417792); European research council (ERC consolidator grant Design2Heal, contract No. 617989); Professor Dietmar W Hutmacher from Institute of Health and Biomedical Innovation (Queensland University of Technology) for his support of TDB for MEW device construction; Björn Schulte from the Dept of Macromolecular Chemistry (RWTH Aachen) for SEC analysis

Additive manufacturing of scaffolds with sub-micron filaments via melt electrospinning writing

The aim of this study was to explore the lower resolution limits of an electrohydrodynamic process combined with direct writing technology of polymer melts. Termed melt electrospinning writing, filaments are deposited layer-by-layer to produce discrete three-dimensional scaffolds for in vitro research. Through optimization of the parameters (flow rate, spinneret diameter, voltage, collector distance) for poly-ϵ-caprolactone, we could direct-write coherent scaffolds with ultrafine filaments, the smallest being 817 ± 165 nm. These low diameter filaments were deposited to form box-structures with a periodicity of 100.6 ± 5.1 μm and a height of 80 μm (50 stacked filaments; 100 overlap at intersections). We also observed oriented crystalline regions within such ultrafine filaments after annealing at 55 °C. The scaffolds were printed upon NCO-sP(EO-stat-PO)-coated glass slide surfaces and withstood frequent liquid exchanges with negligible scaffold detachment for at least 10 days in vitro.

Effect of Statistical Scatter of Spinneret Diameter on the Dynamics of Formation and Uniformity of Elementary Filaments

The method of statistical modeling is used to determine the relationship between the thickness of filaments and the coefficients of variation for time and density. It is shown that the standard deviation of the outgoing flow is directly proportional to these coefficients individually and in combination. The mathematical model which was constructed allows these relationships to be used to design new systems for controlling the passage of a polymer solution through a spinneret.

Electrospun precursor carbon nanofibers optimization by using response surface methodology

Ultrafine fibers were electrospun from Polyacrylonitrile and N,N-dimethylformamide solution to be used as a precursor for carbon nanofibers. An electrospinning set-up was used to collect fibers with diameter ranging from 104 nm to 434 nm. Morphology of fibers and its distribution were investigated by varying Berry's number, charge density, spinning angle, spinneret diameter and collector area. A more systematic understanding of process parameters was obtained and a quantitative relationship between electrospinning parameters and average fiber diameter was established by using response surface methodology. It was concluded that; Berry's number, charge density and spinneret diameters played an important role to the diameter of nanofibers and its standard deviation. Spinning angle and collector area had no significant impact. Based on response surface methodology the optimum Polyacrylonitrile average fiber diameter of 280 nm and 28 nm standard deviation, were collected at 1.6 kV/cm charge density, 8 Berry's number and 0.9 mm spinneret diameter.

Optimization of Process Parameters of Wet-Spun Solid PVDF fibers for Maximizing the Tensile Strength and Applied Force at Break and Minimizing the Elongation at Break using the Taguchi Method

PVDF polymer is well known with its high strength, toughness and piezoelectric properties. It is commonly used in film form for sensor applications, mechanical actuators, energy harvesters, artificial muscles, and membranes. PVDF polymer is also used as hollow fiber membranes in filtration applications, such as nanofiber-web produced using electrospinning and as solid PVDF fiber produced using melt spinning for research purposes. According to a literature study, research on PVDF solid fiber production using wet spinning is limited. This article is about the optimization of the process parameters of wet-spun solid PVDF fibers for maximizing the tensile strength and applied force at break and minimizing the elongation at break using the Taguchi Method. According to the results, the highest applied force at break was achieved when PVDF fiber made from the process parameters of 12 rpm pump speed, 1.5 mm spinneret diameter, 1.0 draw ratio, and 40°C draw temperature. The highest tensile strength was achieved when PVDF fiber was made from the process parameters of 8 rpm pump speed, 1mm spinneret diameter, 2.0 draw ratio, and 40°C draw temperature. The minimum elongation at break was achieved when PVDF fiber was made from the process parameters of 4 rpm pump speed, 1.5 mm spinneret diameter, 2.0 draw ratio, and 25°C draw temperature. These results may prove that process parameters could be used for the further production of the PVDF fibers. Additionally, the Taguchi method was found to be reliable for optimizing the wet spinning of PVDF fibers.

폴리아크릴로니트릴 공중합체의 극세 섬유제조 및 그 물성

The conditions of wet spinning were considered in order to prepare the fine denier of acrylic fiber. Polyacrylonitrile copolymer was synthesized by the copolymerization of acrylonitrile (AN) and methyl acrylate (MA) initiated by an aqueous sulfite-chlorate redox system. Acrylic fiber was manufactured through wet-spinning in a dimethyl formamide (DMF) system. The conditions of wet-spinning were investigated by i-value, spinning speed, diameter of spinneret, draw ratio, water content of spinning dope and morphology of protofiber. The physical properties of fibers were investigated by Instron. In this experiment, the minimum i-value decreased with the decreasing spinneret diameter, an increased spinning speed, and an increased coagulation bath (CBC) concentration. The maximum draw ratio increased with an increased CBC. The optimum CBC and water content of the spinning dope were 60%-65% and 3.5%, respectively. The tenacity at the breaking point increased with a decreased fineness of fiber. The elongation at breaking point was almost the same value as a function of the fineness of fiber.

Experimental research on thermo-direct fiber drawing technique

Given inspiration from the natural hair receptors of animals, sensors based on micro/nano fibers are considered as a significant and promising solution for improving the intelligence and automation of micro robots in the future. In order to develop a novel fabrication method for producing suspended micro polymeric fibers with piezoelectric property between specific positions as a sensitive element of bio-mimetic sensors, this paper introduces the concept and experimental research results of the thermo-direct drawing technique. Piezoelectric fibers are processed by extending viscous volatile PVDF solution within drawing time window and formed after solidifying. The setup and detailed fabrication process of this technique are first presented. The relationship between drawing ratio and the produced fiber diameter as well as the influence of the spinneret diameter are analyzed by both CFD simulation and drawing experiments. At last, an empirical drawing model is discussed based on the simulation and experimental results in order to underlie the fiber fabrication of the future research.

Three-jet electrospinning using a flat spinneret

Electrospinning is a simple but highly versatile technology to produce nanofibers from solutions or melts mostly of polymers using electrostatic forces. A primary challenge facing electrospinning is its low productivity mainly limited by flow rate. In this work, a custom-made three-hole spinneret instead of conventional needles was adopted to enhance the flow rate of electrospinning. Three-jet formation, nanofiber deposition, nanofiber morphology and size were characterized by digital camera and scanning electron microscopy (SEM) as the effects of several governing parameters in electrospinning, including applied voltage from 19.8 to 21.0 kV, working distance from 15.2 to 16.8 cm and flow rate from 6.0 to 9.0 mL/h. It was found that three simultaneous stable jets were ejected from the three-hole spinneret under suitable operating conditions. Moreover, it was found that the fibers collected from the jets from each hole deposited separately in circular spots on a stationary collector. The resultant fibers mostly have an average diameter of less than 300 nm. It has been proved that simple holes on a flat surface can be used to electrospin nanofibers. The three-hole spinneret produces nanofibers at flow rates greater than that in single needle electrospinning. Flow rate has the potential to be easily scaled up by increasing the spinneret diameter and the number of holes.

Velocity, acceleration & jerk in electrospinning

Electrospinning can produce nano-fibers by drawing a polymer jet through a virtual spatio-temporal orifice. The diameter of the virtual orifice at any time or space depends on the velocity at that point, the velocity being determined by the continuity equation. Velocity profiles on silicone jet reveal that acceleration is not a constant, whereas the values fit the model for jerk. The findings should give a handle on the optimization of process parameters. To investigate the other factors that influence velocity (and hence the fiber diameter), the thinning and solidification are modeled. Results reveal that the jet thins drastically in the early stages, for both solution & melt electrospinning; however, thinning can continue till the end of the flight. In solution electrospinning, solvent evaporation during flight results in further thinning of the jet. The model reveals that solution electrospun fibers deposited on the collector could be retaining some residual solvent, limiting its applications. The kinematic model for melt electrospinning computes velocity, fiber diameter, viscosity & temperature. The field gradient expressed in V/m is shown to be equivalent to N/C. In the range where the voltage matches the flow rate (and viscosity), a steady state is attained, resulting in continuous fibers. In this range, the process parameters of flow rate, viscosity or the voltage could be varied to give fibers of uniform diameter. The spool speed has to match the terminal velocity, for producing continuous fibers, to ensure dimensional stability of the product. INTRODUCTION Spinning is the process used for drawing a fiber-forming polymer into filaments by passing through a spinneret. Solution spinning (wet or dry) and melt spinning are the major spinning techniques used in the production of fibers. In dry spinning the solvent evaporates in a spinning tower, resulting in solid fibers; in melt spinning the polymer melt solidifies to give the fiber. Conventional fiber-forming techniques are dependant on the spinneret diameter which may not be reduced indefinitely, due to limitations of the tools used for fabricating them. The major technique that can be used to make fibers thinner than 100 m is electrospinning; the process is capable of giving very long continuous fibers 1-4 . Electrospinning produces very thin fibers by electrostatically drawing a polymer jet through a virtual spatio-temporal orifice. The diameter of the virtual orifice at any time or space depends on the velocity at that point. The velocity is determined at any point by the continuity equation: Q = π r 2 v, where Q is the volumetric flow rate, r is the fiber radius and v is the velocity. END-OF-FLIGHT VELOCITY Dalton et al., have melt electrospun poly-(ethylene glycolblock-e-caprolactone) 5 ; with scanning electron microscopy, they have determined the diameter of the fibers. Using their data and the continuity equation, we have computed the terminal velocities (Table 1). Whether the velocity is built up by constant acceleration or by jerk is investigated in this paper; the findings should give a handle on the optimization of process parameters. Velocity, acceleration & jerk in electrospinning