Abstract:Abstract. Melt spinning of the fibers by supersonic air jet in the Laval nozzle is a novel, efficient and energy saving method of formation of super-thin fibers. In the process, polymer melt is extruded from a row of orifices and fast drawn by the pneumatic forces. In the modelling, air velocity, temperature and pressure distributions are computed from the k-ω aerodynamic model. Computations of the polymer air-drawing dynamics are based on the mathematical model of melt spinning in a single-, thin-filament app… Show more
“…Figure 2 provides an overview of current major nanofiber production technologies and the fiber diameters that have typically been achieved using those methods. Only the most common processes are mentioned and there are many variants of these methods that we do not discuss in detail [42–50]. Fig.…”
Section: Current Manufacturing Processes For Sub-microfibers and Nanomentioning
Sub-microfibers and nanofibers have a high surface-to-volume ratio, which makes them suitable for diverse applications including environmental remediation and filtration, energy production and storage, electronic and optical sensors, tissue engineering, and drug delivery. However, the use of such materials is limited by the low throughput of established manufacturing technologies. This short report provides an overview of current production methods for sub-microfibers and nanofibers and then introduces a new melt-electrospinning prototype based on a spinneret with 600 nozzles, thereby providing an important step towards larger-scale production. The prototype features an innovative collector that achieves the optimal spreading of the fiber due to its uneven surface, as well as a polymer inlet that ensures even polymer distribution to all nozzles. We prepared a first generation of biobased fibers with diameters ranging from 1.000 to 7.000 μm using polylactic acid and 6% (
w
/w) sodium stearate, but finer fibers could be produced in the future by optimizing the prototype and the composition of the raw materials. Melt electrospinning using the new prototype is a promising method for the production of high-quality sub-microfibers and nanofibers.
“…Figure 2 provides an overview of current major nanofiber production technologies and the fiber diameters that have typically been achieved using those methods. Only the most common processes are mentioned and there are many variants of these methods that we do not discuss in detail [42–50]. Fig.…”
Section: Current Manufacturing Processes For Sub-microfibers and Nanomentioning
Sub-microfibers and nanofibers have a high surface-to-volume ratio, which makes them suitable for diverse applications including environmental remediation and filtration, energy production and storage, electronic and optical sensors, tissue engineering, and drug delivery. However, the use of such materials is limited by the low throughput of established manufacturing technologies. This short report provides an overview of current production methods for sub-microfibers and nanofibers and then introduces a new melt-electrospinning prototype based on a spinneret with 600 nozzles, thereby providing an important step towards larger-scale production. The prototype features an innovative collector that achieves the optimal spreading of the fiber due to its uneven surface, as well as a polymer inlet that ensures even polymer distribution to all nozzles. We prepared a first generation of biobased fibers with diameters ranging from 1.000 to 7.000 μm using polylactic acid and 6% (
w
/w) sodium stearate, but finer fibers could be produced in the future by optimizing the prototype and the composition of the raw materials. Melt electrospinning using the new prototype is a promising method for the production of high-quality sub-microfibers and nanofibers.
“…Laval nozzles are important tools in other fields such as powder metallurgy, including gas-assisted atomization (Allimant et al, 2009 andSi et al, 2014), narrow size nanoparticle synthesis (Li et al, 2008 andJung et al, 2008), or inertial separation of particles (Kanaoka et al, 2001). These type of nozzles can be found as well as part of apparatuses developed for studies concerning spray deposition (Jen et al, 2006), formation of super thin fibers (Blim et al, 2014), hydrogen production (Du et al, 2012), laser cutting (Man et al, 1999), homogeneous or binary nucleation (Kim et al, 2004 andTanimura et al, 2010), infrared (Tanimura et al, 1996 andBenidar et al, 2000) or microwave spectroscopy (Oldham et al, 2014), or hypersonic astrophysical jets simulations (Tordella et al, 2011).…”
A detailed description of a new pulsed supersonic uniform gas expansion system is presented together with the experimental validation of the setup by applying the CRESU (French acronym for Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique to the gas-phase reaction of OH radicals with 1-butene at ca. 23 K and 0.63 millibars of helium (carrier gas). The carrier gas flow, containing negligible mixing ratios of OH-precursor and 1-butene, is expanded from a high pressure reservoir (337 millibars) to a low pressure region (0.63 millibars) through a convergent-divergent nozzle (Laval type). The novelty of this experimental setup is that the uniform supersonic flow is pulsed by means of a Teflon-coated aerodynamic chopper provided with two symmetrical apertures. Under these operational conditions, the designed Laval nozzle achieves a temperature of (22.4 ± 1.4) K in the gas jet. The spatial characterization of the temperature and the total gas density within the pulsed uniform supersonic flow has also been performed by both aerodynamical and spectroscopic methods. The gas consumption with this technique is considerably reduced with respect to a continuous CRESU system. The kinetics of the OH+1-butene reaction was investigated by the pulsed laser photolysis/laser induced fluorescence technique. The rotation speed of the disk is temporally synchronized with the exit of the photolysis and the probe lasers. The rate coefficient (k(OH)) for the reaction under investigation was then obtained and compared with the only available data at this temperature.
“…Hassan et al 19 found that applying air constrictors around the primary air jets could keep the maximum air velocity and temperature in a longer distance. Tan et al 20 and Blim et al 21 studied the characteristic of the Laval-die melt-blown air flow by CFD simulation. In addition, melt-blown dies with louvers were designed, 22 and the spinning experiment verified the better effect of fiber attenuation.…”
Section: Introductionmentioning
confidence: 99%
“…Tan et al . and Blim et al studied the characteristic of the Laval-die melt-blown air flow by CFD simulation. In addition, melt-blown dies with louvers were designed, and the spinning experiment verified the better effect of fiber attenuation …”
Melt streams were
attenuated into microfibers by high-speed airflow
during melt blowing. The present work explored the effect of air-slot
width on the fiber diameter and diameter evenness in flush sharp-die
melt blowing. The airflow in different die melt blowing was first
numerically simulated by the CFD approach. Then, the fiber dynamic
whipping was captured by high-speed photography. Finally, a spinning
experiment was implemented and the fiber diameters were measured.
The result reveals that the sharp die with a larger air-slot width
produces fibers with a larger diameter, but the uniformity is obviously
better. This study reveals that the air flow, fiber whipping, and
final fiber diameter are closely related to each other. The quality
control of melt-blown fiber can be carried out by controlling the
fiber whipping motion.
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