Effect Of Spinning Conditions Research Articles

The Effects of Electrospinning Structure on the Ion Conductivity of PEO-Based Polymer Solid-State Electrolytes

To overcome the safety hazard of the liquid electrolytes used in traditional lithium batteries, solid electrolytes have drawn more attention because of their advantages such as non-volatility, easy processing, good mechanical properties, and stability. In this paper, sodium alginate (SA) nanofiber membranes were used as the backbone of PEO-based solid electrolytes. SA nanofiber membranes were prepared by electrospinning with assistance from PEO and cross-linked with calcium ions to construct a nanofiber network skeleton, which provided a guarantee for the stability of the subsequent electrolyte preparation process. The effects of spinning conditions and crosslinking time on the structure and performances of the nanofiber membranes were investigated. Meanwhile, the relationship between the skeleton of nanofiber membranes cross-linked with calcium ions and ion conductivity was investigated. The optimal parameters of the electrospinning process including concentration, voltage, distance, and SA content were discussed, and the fiber diameter and its distribution were analyzed. Furthermore, Fourier transform infrared (FTIR) spectrometer, thermal gravimetric analyzer analysis (TGA), X-ray diffraction (XRD), and energy dispersive spectrometer (EDS) maps were used to characterize the nanofiber membranes and electrolytes. The results showed that the thermal performance of cross-linked nanofiber membranes improved and the crystallinity of the PEO matrix decreased. The ion conductivity of the electrolytes was characterized by electrochemical impedance spectroscopy (EIS) testing, and the results showed that the assembled lithium symmetric battery had a good ion conductivity of 6.82 × 10−5 S/cm at 30 °C.

Preparation of para-aramid aerogel fiber structurally colored by light scattering through wet spinning and supercritical drying

This research is an investigation of the preparation conditions for para-aramid aerogel fibers that are structurally colored by Rayleigh scattering, an angle-independent structural color. It is well known that structural color has the angle dependence of colors. However, there is currently a desire for materials with angle-independent structural color. During the fibers’ spinning process, the microstructures of the fibers are generated. The effect of spinning conditions is investigated by measuring the optical properties of the wet gel fibers. The neutralization speed of negatively charged PPTA fibrils has a significant impact on the formation of the dense microstructure. Spinning under the fast neutralization speed condition makes it possible to achieve the blue-colored fiber derived from Rayleigh scattering. The influence of neutralization speed on the microstructure of the fibers is confirmed by FE-SEM characterization. Furthermore, spinning using a narrow inner diameter needle decreases the whiteness component derived from Mie scattering of the fibers, resulting in a more vivid blue color. The angle-independent structurally colored fibers hold great promise for application in clothing, interiors, and industrial materials.

Preparation, oil adsorption behavior, and mechanism of micro/nanofibrous polycaprolactone membrane prepared through solution blow spinning

In this paper, biodegradable polycaprolactone (PCL) was used as the raw material to prepare micro/nanofibrous polycaprolactone membrane (PCLM) through solution blow spinning (SBS) technology. The effects of spinning conditions (distance, gas pressure, and spinning solution concentration) on PCLM structures were investigated. The obtained membranes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, water contact angle, and thermogravimetric analysis instrument. The oil adsorbency and reusability of PCLM were measured. The oil adsorption capacity of PCLM for motor oil, peanut oil, and diesel oil was 15.93, 14.81, and 12.86 g·g−1, respectively. After 10 times of reuse, the adsorption capacity for motor oil, peanut oil, and diesel oil could still remain at about 80% of the first cycle. The kinetic and thermodynamic studies showed that the adsorption conformed to the first‐order kinetic model and Freundlich model. Thermodynamic parameters for oil adsorption ΔGθ, ΔHθ, and ΔSθ indicated the oil adsorption of PCLM was a spontaneous and physisorption process.

The Impact of Shear and Elongational Forces on Structural Formation of Polyacrylonitrile/Carbon Nanotubes Composite Fibers during Wet Spinning Process.

Wet spinning of polyacrylonitrile/carbon nanotubes (PAN/CNT) composite fibers was studied and the effect of spinning conditions on structure and properties of as-spun fibers influenced by the presence of CNTs investigated. Unlike PAN fibers, shear force had a larger effect on crystalline structure and physical and mechanical properties of PAN/CNT composite fibers compared to the elongational force inside a coagulation bath. Under shear force CNTs induced nucleation of new crystals, whereas under elongational force nucleation of new crystals were hindered but the already formed crystals grew bigger. To our knowledge, this key effect has not been reported elsewhere. At different shear rates, strength, Young’s modulus and strain at break of PAN/CNT as-spun fibers were improved up to 20% compared to PAN fibers. Application of jet stretch had less influence on physical and mechanical properties of PAN/CNT fibers compared to PAN fibers. However, the improvement of interphase between polymer chains and CNTs as a result of chain orientation may have contributed to enhancement of Young’s modulus of jet stretched composite fibers.

Development and characterizations of polylactic acid (PLA) and polyglycolide acid (PGA) monofilaments for acupoint catgut embedding therapy applications

Polylactic acid (PLA) and polyglycolide acid (PGA) are known for good biocompatibility. These features have resulted into significant academic and industrial research interest in various areas. However, in the acupoint catgut embedding therapy field, the existing PLA and PGA can't satisfy usage requirements due to their poor properties. This work designed novel melt-spinning system to produce different PLA and PGA monofilaments, and effects of spinning conditions on their comprehensive performances were characterized. The results showed that samples had the smooth surfaces and diameters decreased with spinning parameters. PLA-2 (Strength = 78.63 cN; Elongation = 57.28%) and PGA-2 (Strength = 57.34 cN; Elongation= 18.42%) perform the best mechanical properties. All the samples were non-toxicity, and PLA group degraded much slower than that of PGA group. In conclusion, this melt-spinning system showed potential in ACET application the optimum parameters (v = 150 m/min, n = 6) were proved to have the higher prospect.

Study on the effect of spinning conditions on the performance of PSf/PVP ultrafiltration hollow fiber membrane

Asymmetric, porous ultrafiltration polysulfone (PSf) hollow fiber membranes were fabricated via the dry-wet phase inversion spinning technique specifically for haemodialysis membrane. The objective was to discover the suitable spinning condition for the fabrication of ultrafiltration hollow fiber membrane with desired sponge-like structure. During haemodialysis procedure, uremic toxins such as urea and creatinine range from size 10,000-55,000 Da needs to be excreted out from the blood. While, proteins such as albumin (66,000 Da) need to be retained. The physical structure or morphology of a fabricated membrane is a major concern in determining the efficiency of a dialysis membrane. Different type of membrane morphology will give a different result in term of its permeability and clearance efficiency. The phase inversion spinning technique is suitable in producing ultrafiltation (UF) membrane where the average pore size of the fabricated membrane is in the range of 0.001 – 0.1 µm. However, there is many factors need to be controlled and manipulated in the phase inversion technique. In this study, the effect of the PVP on membrane pore size and performances were analysed. The contact angle measurement was measured to determine the hydrophilicity of the fibers. The hydrophilic polymer is favorable to avoid fouling and increase its biocompatibility. Furthermore, the diameter of the hollow fibers was determined using a scanning electron microscope (SEM). The effects of different morphology of the hollow fibers on the performance of the membranes were evaluated by pure water flux and BSA rejection. Both techniques were tested using permeation flux system. Based on the results obtained, it is found that the finger-like macrovoids in PSf hollow fiber membranes were suppressed by adding 8% PVP (Mw of 360 kDa) into the spinning dope solution as the result of a drastic increase in dope viscosity. On top of that, fiber spun with 8% PVP show more porous structure which contribute to higher permeability of the membrane. The result of this study can benefit to the membrane field of research especially in membrane technology for haemodialysis application.

Helical hollow fibers via rope coiling: Effect of spinning conditions on geometry and membrane morphology

Helical hollow fiber membranes from poly(ether sulfone) were spun via dry-wet spinning, making use of the liquid rope coiling phenomenon. The polymer solution composition was changed by varying the coagulation value and adding PEG400 as pore former. The bore liquid composition, outer coagulation bath temperature, air gap, polymer dope and bore liquid flowrates were varied to map the conditions where helical fibers form. It was observed that increasing air gap changed fiber geometry from straight to helical. Increasing the outer coagulation bath temperature caused helical geometries to become irregular or straight under identical spinning conditions, possibly due to the higher water vapour absorption in the air gap. Regularly helical fibers could, however, be spun with a coagulation bath at 50 °C under a variety of conditions. Comparing fibers spun under the same conditions with different solutions, it was observed that as the solution's viscosity increased, the geometry shifted towards helical. Increasing the bore liquid solvent strength so as to form the skin on the bore side yielded straight fibers due to the fast solidification of the fibers before curling and all helical fibers fabricated had a denser skin on the shell side. During filtrations of yeast suspensions, the helical fibers experienced less fouling with the feed on either the bore or the shell side of the membrane, which shows that using liquid rope coiling to spin helical fibers is a promising, practical method of alleviating fouling in membrane filtrations.

Effect of melt spinning conditions on the fiber structure development of polyethylene terephthalate

The effects of spinning conditions on fiber properties are not well explained by the fiber structures because the birefringence, crystallinity, and SAXS patterns are often similar. In this study, the effects on the fiber structure development of polyethylene terephthalate after necking was analyzed by simultaneous WAXD/SAXS measurements. An X-shaped SAXS pattern was observed for all fibers drawn at the minimum draw ratio. In contrast, by drawing under a drawing stress of 100 MPa, the strong diffraction of the smectic phase and an obviously larger long period less than 1 ms after necking were observed for fibers spun at 500–1500 m/min, while almost no smectic phase was observed for fibers spun at 2000 m/min. A higher crystallization rate and clear draw ratio dependence of crystallization rate were also observed for the fiber spun at 2000 m/min. The clear differences in structure development can explain their differences in tensile strength and thermal shrinkage.

Controlling micro‐ and nanofibrillar morphology of polymer blends in low‐speed melt spinning process. Part III: Fibrillation mechanism of PLA/PVA blends along the spinline

ABSTRACTThe effects of spinning conditions on the fibrillation process of poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) polymer blends in an elongational flow within the fiber formation zone are systematically and thoroughly investigated. By considering the relationship between the changes in filament parameters with the focus on the maximum axial strain rate (ASR) and tensile stress at maximum ASR and the morphological evolution of the dispersed PLA phase along the spinline, the fibrillation process from rod‐like to nanofibrillar structures of the dispersed PLA phase in a binary blend with PVA matrix is elucidated. The final morphology of the dispersed PLA phase in PLA/PVA blends is controlled by the changes in the spinning conditions. The lengths and diameters of the PLA fibrils are caused not only by the deformation of their initial sizes but also by the combination of the deformation, coalescence, and break‐up process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44259.

Recent progress in polymeric hollow-fibre membrane preparation and applications

Hollow-fibre membranes are of great commercial interest, with many applications. This article reviews recent progress made – mostly during the last eight years – in polymeric materials for hollow-fibre spinning, the spinning method and the effects of spinning conditions. It was found that amongst the large number of available polymers only a limited number has been used for membrane development. Hollow-fibre surface modification and the incorporation of nanoparticles in mixed-matrix membranes have been attempted to enhance performance. Attempts have also been made to use hollow-fibre membranes in relatively novel membrane-based separation processes, such as membrane distillation and forward osmosis, and in membrane contactors. Progress in these areas is also summarised.

Fabrication of PVDF hollow fiber membranes: Effects of low-concentration Pluronic and spinning conditions

Due to the unique properties of amphiphilic Pluronic block copolymers, they have been blended with other polymers such as PVDF to prepare membranes. Considering the stability issue, the strong pore-forming ability of Pluronic F127, and the mechanical strength of the resultant membranes, Pluronic/LiCl mixed additive consisting of a very low concentration of Pluronic has been used in this study. The effects of spinning conditions on PVDF hollow fiber fabrication have also been studied. It is found that the use of merely 0.2wt% of Pluronic is sufficient to impose significant impacts on the morphology, filtration performance, and mechanical properties of the resultant fibers. Hollow fibers spun using higher coagulant temperature, higher take-up speed, and water as the bore fluid exhibit better mechanical properties and filtration performance. PVDF hollow fiber membranes with PWP of 1180L/m2hMPa and MWCO of 5kDa were obtained when spun with optimized spinning conditions and using 3wt% of LiCl and 0.2wt% of Pluronic as the mixed additive. The fibers can withstand a pressure of 0.55MPa from the lumen.

Preparation and Performance of Polysulfone Hollow Fiber Ultrafiltration Membranes

Polysulfone (PSF) hollow fiber ultrafiltration membranes were successfully prepared by dry-wet spinning technology. Dimethylacetamide (DMAC) was used as a solvent, water was used as bore liquid and coagulation bath, polyvinylpyrrolidone (PVP) was used as polymeric additive. The effects of spinning conditions on membrane structures and properties were investigated in present study. The results indicated that with the increase of PVP concentration, pure water flux increased and developed finger-like pores were formed. High coagulation bath temperature restricted pure water flux, 30°C was the best for the preparation of high-performance ultrafiltration membranes. When the air length was 11cm, the membrane comprehensive performance was the best.

Solution blowing nylon 6 nanofiber mats for air filtration

Solution blowing process is a new nanofiber fabricating method with high productivity. In the present study, nylon 6 nanofiber mats were solution blown and the effects of spinning conditions on nanofibers morphology were investigated. The fiber diameter ranged from 150 to 750 nm which was affected by solution concentration, gas pressure and solution feeding rate. The solution blown fibers were three-dimensional curly which made loose construction in bulk. The filtration performance of solution blown mats was evaluated. The tested solution blown nanofiber mats showed high filtration efficiency of 83.10 % to 93.45 % for 0.3 µm particles filtration and extremely low pressure drop of 15.37 to 30.35 Pa. The results indicate the solution blown nanofiber mats will find potential application of high efficiency and low resistance filter.

Fabrication of silk sericin nanofibers from a silk sericin-hope cocoon with electrospinning method

In this study, silk sericin nanofibers from sericin hope-silkworm, whose cocoons consist almost exclusively of sericin were successfully prepared by electrospinning method. Scanning electron microscopy (SEM) was used to observe the morphology of the fibers. The effect of spinning conditions, including the concentration of sericin cocoon solution, acceleration voltage, spinning distance and flow rate on the fiber morphologies and the size distribution of sericin nanofibers were examined. The structure and physical properties were also observed by Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The optimum conditions for producing finely thinner fibrous sericin nanofibers without beads were the concentration of sericin solution above 6–8wt%, acceleration voltage ranging from 25 to 32kV, spinning distance above 9cm, and flow rate above 0.06cmmin−1. The mean diameter of as spun sericin fibers varied from 114 to 430nm at the different spinning conditions. In the as-spun fibers, silk sericin was present in a random coil conformation, while after methanol treatment, the molecular structure of silk sericin was transformed into a β-sheet containing structure. Sericin hope nanofiber demonstrated thermal degradation at lower temperature than the sericin hope cocoon, which probably due to the randomly coiled rich structure of the sericin hope nanofiber.

Effect of spinning conditions on the structure and performance of hydrophobic PVDF hollow fiber membranes for membrane distillation

Microporous hydrophobic poly(vinylidene fluoride) (PVDF) hollow fibers were prepared via dry-jet wet phase-inversion method using N,N-dimethylacetamide (DMAc) as solvent, LiCl and PEG-400 as non-solvent additives in the polymer dopes. The effects of various preparation conditions, including the concentration of polymer and additives, bore liquid temperature, air gap, take-up speed and dope extrusion rate on the morphology and properties of membrane were studied. The prepared membranes were characterized through scanning electron microscopy (SEM) observation, gas permeation measurement, and tensile property test. The permeate flux of membrane in both vacuum membrane distillation (VMD) and direct contact membrane distillation (DCMD) for desalination was tested. It is found that the permeation property of membrane is mainly determined by membrane porosity, especially effective porosity. The formation of the sponge structure reduced VMD flux more fiercely than DCMD flux. Under the synergetic effect of PEG-400/LiCl, high permeate flux and relatively high mechanical strength of membrane can be simultaneously achieved. There exist the best ranges of bore liquid temperature and of air gap distance for relatively high permeate flux of membrane.

Supramolecular structures and dyeing properties of poly(ethylene terephthalate) industrial yarns for seat‐belt webbings

The effects of spinning conditions and additives on the physical and dyeing properties of poly(ethylene terephthalate) industrial yarns were investigated by analysing their supramolecular structures. Four poly(ethylene terephthalate) yarns for seat-belt webbing were prepared with different formulations and under different spinning conditions. Instrumental characterisation of the internal morphologies and physical properties confirmed that the structural characteristics are influenced by the draw ratio, heat-setting temperature and copolymer added, and that there are close correlations between the supramolecular structure and the physical and dyeing properties. In particular, the draw ratio was the most dominating factor, influencing both the mechanical properties and the dyeability.

Optimization of membrane structure using the spin-coating method

Spin-coating is a preferred method for application of thin and uniform films on flat substrates, it is used extensively in microlithography. For polymeric membranes prepared by the immersion-precipitation method, the solvent-nonsolvent mass transfer kinetics always governs the ultimate membrane structure to a large extent. In this paper, the effects of spinning conditions on the mass transfer kinetics and thus the structure and performance of very thin and smooth membranes were investigated. The results indicated that the membrane structures can be regulated in a relatively large range through adjusting the spinning conditions (spinning speed, spinning time, acceleration process). With proper control, formation of membranes with round-pore surfaces or nodular surfaces can be achieved.

Effect of spinning conditions on the mechanical properties of PA6/MWNTs nanofiber filaments

Carbon nanotube (CNT ) reinforced composite materials is a hot research issue now , but CNT/polymer composite nano-scale fibers still cannot be obtained readily, not mention to successfully prepare continuous CNTs/polymer composite nano-scale fiber filaments manufactured by electrospinning. In this paper, continuous filaments constructed of nano-scale PA6/MWNTs fibers in single-axis orientation were obtained by an improved wet-electrospinning technique. The effects of the concentrations of MWNTs, spinning speed and post-drawing on the mechanical properties of PA6/MWNTs nanofiber filaments were studied. The results show that when the concentrations of MWNTs is below 0.8 wt%, the increase of MWNTs content enhances the Young’s modules and breaking stress but reduces the breaking strain, while the breaking stress decreases when the MWNTs concentration exceeds 0.8 wt%. The Young’s modules and breaking stress increased as the spinning speed raised at the range of 1.8–9.0 m/min, but declined when the speed exceeded 9.0 m/min. The mechanical properties of the as-spun filaments can be improved by either dry or wet post-drawing, and the breaking stress of the wet post-drawn filaments was improved 2.64 times while that of the dry post-drawn filaments 2.28 times.

Effect of spinning conditions on the mechanical properties of polyacrylonitrile fibers modified with carbon nanotubes

AbstractCarbon nanotubes (CNTs) were used to modify polyacrylonitrile (PAN) polymer. The PAN/CNT composite fibers were spun from dimethylformamide solutions containing different types of CNTs. The effect of nanotube addition to the fiber precursor on the resulting mechanical properties is discussed. In this study, we examined the relationship of the rheological properties of PAN spinning solutions containing various types of CNTs and the tensile strength of the resulting PAN fibers. The presence of CNTs in the PAN spinning solution enhanced its deformability during the drawing stage. This effect resulted in a higher tensile strength in the fibers containing nanotubes, as compared to the pure fibers. The use of a three‐stage drawing process resulted in a significant increase in the tensile strength of PAN fibers modified with multiwalled nanotubes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effects of spinning conditions on convergent point in rotor-spun composite-yarn spinning process

The forces acting on the components in rotor spinning system cannot shift the convergent point, which can be changed, however, by adjusting speeds of the components. Experimental verification is made, and the result is useful for machine users and engineers.