High-speed Spinning Process Research Articles

A critical review on recent developments and solutions in the high-speed ring spinning process

Twist plays an important role in textile technology, particularly in the production of staple yarn structures. Due to the higher yarn quality and flexibility of the process, most short staple fiber yarns are produced in the ring spinning process in comparison to other high-speed spinning processes, such as rotor or air jet spinning. To impart twist in the yarn, the ring/traveler system, rotor and air jet nozzle are used in the ring, rotor and air jet spinning processes respectively. However, the productivity of the ring spinning process is limited significantly due to the frictional heat generated between the ring and traveler, especially at higher angular spindle speeds, which is crucial for the spinning of man-made fibers. This paper aims to describe the recent developments and solutions for increasing productivity in the ring spinning process in a systemic way. To reduce the friction, different topologies and surface modifications in the ring/traveler system were made to increase the angular spindle speed of maximum 23,000 rpm. To eliminate the friction, the twisting element was made of an air bearing or magnetically elevated rings were developed by replacing the ring/traveler system completely, thus permitting a higher angular spindle speed of up to 50,000 rpm. Further approaches deal with cap, loop and nova spinning or Nu-Torque technology to reduce yarn tension or residual torque in the yarn, respectively. The results of the presented work reveal the potential of different developments, especially in the field of twisting system, so that the productivity of ring spinning can be increased drastically.

Influence of Chain Extenders on Recycled Standard and Opaque PET Rheology and Melt-Spun Filament Properties

This work aims to evaluate the spinnability of recycled poly(ethylene terephthalate) (rPET) modified by chain extenders. Pyromellitic anhydride (PMDA), JONCRYL ADR 4400, 2,2′-bis(2-oxazoline) (BOZ), and 1,3-phenylene-bis-oxazoline (PBO) were used from 0.1 to 1 wt% on transparent postconsumer PET bottle flakes and opaque rPET flakes containing TiO2 particles. The created molecular architectures were characterized in the first section. Second, their spinnability was assessed via a pilot high-speed spinning process. The corresponding shear rheology, intrinsic viscosity, and elongational rheology were reported. It was observed that PMDA and JONCRYL induce a more drastic increase in melt strength and melt elasticity than BOZ and PBO due to chain branching. In a second step, melt-spun filaments were produced with a low content of chain extenders on standard rPET and opaque rPET matrices. Finally, their degree of crystallinity, molecular orientation, and mechanical properties were determined. PMDA and JONCRYL strongly decrease the spinnability and, consequently, the properties of filaments. However, BOZ improves the opaque rPET filaments’ tenacity while decreasing their degree of crystallinity.

An in situ surface modification method of ultra-high molecular weight polyethylene fiber on the basis of dry gel-spinning technique

A novel in situ surface modification strategy of ultra-high molecular weight polyethylene (UHMWPE) fiber is proposed, which is related to the dry gel-spinning technique and the directional entrapping modification. The surface modification, with poly (ethylene oxide) monooleate (OEO) as the modifier, applied a short entrapping time combined with a long storage period to match the high-speed spinning process. Swelling treatment, contact angle and XRD results show that the swollen fibers with swelling degrees between 6.4 and 9.6 wt% are suitable for the surface modification, via which modifier molecules can be facilely embedded into the amorphous regions of swollen surfaces. The modified surface acquires high polarity with a contact angle of 57.2° under conditions of the entrapping time of 60 s and storage period of 12 h. Large micelles of the OEO modifier, induced by great modifier concentrations and high storage temperatures, are proved to be helpful for the surface modification. The introduction of vinyl group in the modifier (oleate of OEO) together with the utilization of benzoyl peroxide (BPO) in the surface modification greatly reinforces the modifier fixation in modified surfaces. The modified fibers give rise to 43.5% elevation of the impact strength of epoxy resin composite relative to unmodified fibers, because of the polar acquirement on fiber surfaces.

Aminolysis of Various Aliphatic Polyesters in a Form of Nanofibers and Films.

Surface functionalization of polymer scaffolds is a method used to improve interactions of materials with cells. A frequently used method for polyesters is aminolysis reaction, which introduces free amine groups on the surface. In this study, nanofibrous scaffolds and films of three different polyesters–polycaprolactone (PCL), poly(lactide-co-caprolactone) (PLCL), and poly(l-lactide) (PLLA) were subjected to this type of surface modification under the same conditions. Efficiency of aminolysis was evaluated on the basis of ninhydrin tests and ATR–FTIR spectroscopy. Also, impact of this treatment on the mechanical properties, crystallinity, and wettability of polyesters was compared and discussed from the perspective of aminolysis efficiency. It was shown that aminolysis is less efficient in the case of nanofibers, particularly for PCL nanofibers. Our hypothesis based on the fundamentals of classical high speed spinning process is that the lower efficiency of aminolysis in the case of nanofibers is associated with the radial distribution of crystallinity of electrospun fiber with more crystalline skin, strongly inhibiting the reaction. Moreover, the water contact angle results demonstrate that the effect of free amino groups on wettability is very different depending on the type and the form of polymer. The results of this study can help to understand fundamentals of aminolysis-based surface modification.

Structural factor of nanoparticles in the stress-induced crystallization of poly(ethylene terephthalate)

The crystallization behavior of poly(ethylene terephthalate) (PET) nanocomposites with clay and trisilanol isobutyl-polyhedral oligomeric silsesquioxane (TPOSS) in the high-speed spinning process was investigated in terms of take-up speed and content of nanoparticles. The spherical TPOSS promoted the crystallization of PET. On the other hand, the plate-like clay with the aspect ratio of 250 suppressed it. At the take-up speed of 3.5 km/min, the crystallinity of the PET nanocomposite containing 1 wt% of clay was 23%, much lower than 48% of neat PET and 57% of the PET nanocomposite containing 2 wt% of TPOSS. The 2D-WAXS analysis revealed that the anisotropic clay nanoparticles aligned parallel to the fiber axis even in the fiber prepared from the free-fall spinning process. Increasing the take-up speed of spinning further increased the degree of orientation of the particle. Because of the suppressed crystallization of PET by the highly oriented clay nanoparticles, the fiber of the PET/clay nanocomposite did not give any characteristic 2D-SAXS pattern over the take-up speed range examined, indicating the absence of tilted lamellar stacks. In the fibers of neat PET and PET/TPOSS nanocomposites, however, an X-shaped 4-point pattern was obtained at low take-up speeds, which was converted to the scattering pattern of an equatorial streak with the inverse triangular scatterings in the meridional direction at high take-up speeds. The transition of the 2D-SAXS pattern shape took place at the take-up speed of 4.5 km/min for neat PET which was shifted to the lower speeds of 4 and 3.5 km/min by adding 1 and 2 wt% of TPOSS, respectively.

Forming method of axial micro grooves inside copper heat pipe

The high-speed oil-filled ball spinning and drawing process was put forward to manufacture the axially grooved heat pipe with highly efficient heat-transfer performance, and the forming mechanism of micro-grooves inside the pipe was investigated. The key factors influencing the configurations of micro-grooves were analyzed. When the spinning depth varies between 0.4 mm and 0.5 mm, drawing speed varies from 200 mm/min to 450 mm/min, rotary speed is beyond 6 000 r/min and working temperature is less than 50 °C, the grooved tubes are formed with high quality and efficiency. The ball spinning process uses full oil-filling method to set up the steady dynamic oil-film that reduces the drawing force and improves the surface quality of grooved copper tube.

Experimental study of oil-filled high-speed spin forming micro-groove fin-inside tubes

This paper presents an oil-filled high-speed spinning process of manufacturing micro-groove fin-inside tubes. In spinning, a high-pressure oil-film, which squeezes the tube outer-wall, is formed as the spinning speed increases. A floating mandrel extrudes the tube inside wall to form the micro-grooves/fins continuously. By experiments of spinning micro-groove fin-inside tubes, this paper analyzes the influences of each process parameter on the formation quality, and optimizes each parameter. The experimental results show that the dynamic pressure can significantly improve the stability of spinning and the quality of finished surface; the minimum thickness of oil-film is decided by the spinning speed and the oil viscosity directly. In the case of full oil dynamic lubrication, there is no obvious scrape on tube surfaces. The main factors affecting the groove depth and the surface roughness are the ratio ( α) of the wall thickness of the tube before drawing to the finished one, the material plasticity, the ratio ( β) of drawing to spinning, the spinning speed ( n), and lubricating state, etc. The axial drawing force mainly depends on the friction between the floating mandrel and the tube internal wall, the friction between the reducing mold and the outer surface, and plastic deformation resistance in the reducing mold area and spinning area as well.

The investigation of irregular inner skin morphology of hollow fiber membranes at high-speed spinning and the solutions to overcome it

In the fabrication of hollow fiber membranes, a high-speed spinning is important to maximize the productivity and minimize the production cost. However, the high-speed spinning process has been shown to influence the morphology of the resultant fibers, especially inner layer of the fibers. For the first time, we report that the increase in the take-up speed results in the deformation of inner shapes of the fibers. This phenomenon is not desirable as it results in the formation of low mechanical strength fibers. It is hypothesized that the phenomenon occurs due to the formation of vacuum condition in the lumen side of the fiber, which may be due to rapid formation of dense skin inner layer. With increasing take-up speed the inner surface becomes denser leading to insufficient bore fluid supply which promotes more vacuum condition in the lumen side. Four possible solutions were proposed to eliminate the inner layer deformation phenomena, i.e. (1) by increasing the bore fluid flow rate, (2) by chemical modification of the bore fluid, (3) by simultaneously increasing dope and bore flow rates while maintaining a constant ratio between them and (4) by simultaneously increasing bore and dope flow rates in the same order with the increase in take-up speed. The increase in bore fluid flow rate can effectively eliminate the deformation. The addition of the solvent to the bore fluid can also eliminate the deformation when 70 wt.% NMP/water was used as bore fluid. No inner layer deformation was observed when dope and bore flow rates were increased up to 4 and 3 ml/min, respectively. However, the first three approaches may have negative side effects. The fourth approach gives us the most promising results. Even after increasing take-up speed up to 470% from its original take-up speed, the resultant fibers show no irregular formation at inner layer morphology and no changes in their inner and outer diameter. Thus, it can be said that by utilizing this approach, more flexible and easy control over fibers can be achieved.

High-speed fiber spinning process with spinline flow-induced crystallization and neck-like deformation

The dynamics and stability of the high-speed fiber spinning process with spinline flow-induced crystallization and neck-like deformation have been studied using a simulation model equipped with governing equations of continuity, motion, energy, and crystallinity, along with the Phan-Thien–Tanner constitutive equation. Despite the fact that a simple one-phase model was incorporated into the governing equations to describe the spinline crystallinity, as opposed to the best-known two-phase model [Doufas et al. J Non-Newton Fluid Mech, 92:27–66, 2000a]; [Kohler et al. J Macromol Sci Phys, 44:185–202, 2005] that treats amorphous and crystalline phases separately in computing the spinline stress, the simulation has successfully portrayed the typical nonlinear characteristic of the high-speed spinning process called neck-like spinline deformation. It has been found that the criterion for the neck-like deformation to occur on the spinline is for the extensional viscosity to decrease on the spinline, so that the spinning is stabilized by the formation of the spinline neck-like deformation. The accompanying linear stability analysis explains this stabilizing effect of the spinline neck-like deformation, corroborating a recent experimental finding [Takarada et al. Int Polym Process, 19:380–387, 2004].

Numerical Simulation of Fiber Spinning Process with Structure Evolution of Polymer Chains

Numerical simulation of the high-speed fiber spinning process was carried out based on a two-phase microstructure model. Calculation predicts not only the variation of parameters along the spinline, but also the radially distribution of flow field variables, such as temperature, crystallinity and molecular structure. Considering the combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymer under various spinning conditions. The structural change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Moreover, a three-dimensional (3D) simulation approach was also established to predict the complex fiber shape given the spinneret geometry under the actual processing conditions. The influences of surface tension and the take-up velocity on the final fiber shape are predicted numerically.

Structural Modification of Polyester Fibers in Supercritical Carbon Dioxide Fluid

Several types of polyester fibers, i.e. high speed spun (HSS) fibers, partially oriented yarns (POY), and fully oriented yarns (FOY), were subjected to the supercritical CO2 fluid treatment (SFT) at 120deg, 20MPa for 1 h and structural modifications were investigated. Large shrinkage and not a small amount of oligomer deposition on the fiber surface were observed for POY and FOY. On the contrary, as for HSS fibers produced at a spinning speed of 6 km/min the shrinkage was suppressed within 2 % as compared with an initial fiber length and the oligomer deposition could hardly be observed. The shrinkproof property for HSS fibers seems to be closely related to the well developed fibrous structure. Such structure can be easily confirmed via the alkaline etching. The oligomer migration can be lowered by accelerating the orientation-induced crystallization rate on the high speed spinning line and disordering the molecular orientation in amorphous regions. In addition ultra-crystallites formed in amorphous regions during SFT will also be effective for the suppression to the oligomer migration. The disordered macromolecules and the ultra-crystallites formed in amorphous regions will develop a network-like structure that suppresses the oligomer migration. Therefore, a novel polyester fiber suitable for the supercritical CO2 fluid dyeing is producible by controlling the fibrous structure and designing the amorphous regions using the high speed spinning process.

Biodegradable fibres spun from poly(lactide) generated by reactive extrusion

Poly(lactide) (PLA) was spun both in a high speed spinning process with take-up velocities of 1000–5000 m min −1 and in a spin drawing process at draw ratios of 4–6. The effect of the melt spinning conditions on the development of the structural hierarchy in the fibres and the relations to the textile physical properties were investigated. The PLA fibres were characterised with regard to the degree of crystallinity by DSC and WAXS, the orientation by WAXS and birefringence, and the stress–strain behaviour. The maximum physical break stress and the E-modulus observed in the spin drawn fibres were about 490 MPa and 6.3 GPa, respectively, at an elongation at break of 30%. The PLA was a copolymer of l-lactide (92 wt.%) and meso-lactide (8 wt.%) and was generated by reactive extrusion polymerisation. The PLA virgin pellets were analysed regarding their degradation during the spinning processes. Their thermal and rheological properties were determined by DSC and dynamic rheological measurements, respectively, to derive suitable parameters for the melt spinning processes.

Melt Processing of a New Biodegradable Synthetic Polymer in High-Speed Spinning and Underpressure Spunbonding Process

A new biodegradable synthetic polyesteramid (PEA) was characterized by means of thermogravimetry (TG) differential scanning calorimetry (DSC) and dynamic rheological measurements. Two glass transition ranges at about −33 and 38°C and a melting enthalpy of 33 J/g were measured, indicating that PEA is an immiscible blend of two components with a small crystalline part. The material was spun in a high-speed spinning process within the range of 2,000–6,000 M/min and an underpressure spunbonding process within the range of 3,600–7,700 M/min. The textile physical properties of the fibers were 100 MPa tenacity at an elongation at break of 30%, and an E-modulus of 0.5 GPa. The mass per unit area of the spunbonded nonwovens ranged from 70–159 g/M2. The strength of the spunbonded nonwovens was 28–51 N and 42–74 N in machine and cross direction, respectively. The air permeability of the nonwovens decreased at high air velocities and more fineness of the filaments from 1240–380 l/M2 s.

617 高速溶融紡糸における冷却風と繊度ムラ(流体工学XII)

617 高速溶融紡糸における冷却風と繊度ムラ(流体工学XII)

Intrinsic Birefringence of γ-Form Crystal of Nylon 6: Application to Orientation Development in High-Speed Spun Fibers of Nylon 6

The intrinsic birefringences of the α- and the γ-form crystals of nylon 6 were calculated from the atomic coordinates and the bond polarizabilities using the Lorentz-Lorenz equation. The intrinsic birefringence of the γ-form crystal was found to be significantly smaller than that of the α-form crystal. Those values were applied to the evaluation of the orientation function of the amorphous phase of the nylon 6 fibers produced by the high-speed spinning process. The molecular orientation in the amorphous phase increased to the maximum point and then decreased with the spinning speed. These results suggested that an inhomogeneous structure in the fiber was formed for the higher take-up speed.

Intrinsic Birefringence of γ-Form Crystal of Nylon 6: Application to Orientation Development in High-Speed Spun Fibers of Nylon 6

The intrinsic birefringences of the α- and the γ-form crystals of nylon 6 were calculated from the atomic coordinates and the bond polarizabilities using the Lorentz-Lorenz equation. The intrinsic birefringence of the γ-form crystal was found to be significantly smaller than that of the α-form crystal. Those values were applied to the evaluation of the orientation function of the amorphous phase of the nylon 6 fibers produced by the high-speed spinning process. The molecular orientation in the amorphous phase increased to the maximum point and then decreased with the spinning speed. These results suggested that an inhomogeneous structure in the fiber was formed for the higher take-up speed.

ポリプロピレンの高速溶融紡糸過程における分子配向形成のオンライン計測

In order to clarify the mechanisms of molecular orientation in high-speed melt spinning of polypropylene (PP), the change of birefringence along the spinline was analyzed through the simultaneous on-line measurement of the diameter and optical retardation profiles. The optical retardation was evaluated using an optical system with a rotating polarizer, polarizing filters, quarter-wave plates and a He-Ne laser as the light source. The birefringence increased only slightly in the upstream portion of the spinline. On the other hand, there was a steep increase of birefringence, which became more significant with an increase in the take-up velocity, near the solidification point where crystallization appears to start. An additional increase of birefringence was notably observed in the downstream portion of the spinline where the thinning of the spinline was already completed. The as-spun PP fibers also showed a gradual increase of birefringence even after the spinning, indicating that the increase of birefringence after the solidification of the spinline was caused by the change in the super-structure of the fibers, not by the increase in tensile stress along the spinline because of the accumulation of the air-friction force. To analyze the applicability of the stress-optical law, tension and temperature profiles of the spinline were calculated based on the experimental results of the diameter profiles. The small increase of birefringence in the molten state was found to be due to the low stress-optical coefficient of PP. It was also found that at take-up velocities above 1km/min the steep increase of birefringence started at the position where the tensile stress of the spinline exceeded about 1MPa. These results suggest that the orientation-induced crystallization of the PP spinline starts at this stress level and also that the development of birefringence of PP fibers in the high-speed spinning process is significantly affected by the crystallization.

Investigation of the high speed spinning process of poly(ethylene terephthalate) by means of synchrotron X-ray diffraction

Measurements of wide-angle diffraction during high speed spinning of poly(ethylene terephthalate) (PET) have been performed using synchrotron radiation. The experimental set-up has been improved so that it became possible to determine the degree of crystallinity, crystallite orientation and fiber diameter along the spin line. For take-up speeds of 3600 m/min and higher, the crystal reflections appeared at a distance of 40 cm from the spinneret, just after the necking region. The crystallization speed increases proportional to increasing take-up speed. For the take-up speeds investigated, this results in a constant crystallinity profile when measured as a function of the distance from the spinneret. The final fibers exhibited an extraordinarily high degree of crystallinity, which has been attributed to the high molecular weight of the polymer. Below 3500 m/min, no crystallization and no necking could be detected up to a distance of 90 cm from the spinneret. The results showed that necking and crystallization were closely coupled. No orientation of the amorphous matrix prior to crystallization could be detected by means of X-ray diffraction. Moreover, the orientation of the crystallites was constant along the spin line.

Effect of Liquid Isothermal Bath in High-Speed Melt Spinning of Poly(ethylene 2,6-naphthalene dicarboxylate).

The high-speed melt spinning process of poly (ethylene 2,6-naphthalene dicarboxylate) (PEN) was modified using a liquid isothermal bath (LIB) which was kept at a liquid temperature of 150 or 170°C. The structure and mechanical properties of the as-spun fibers thus produced in the take-up velocity range of 0.5 to 7.0 km/min were characterized. The fiber structure development in the low take-up velocity region was promoted by the use of the LIB and the promotion becomes more prominent by raising the liquid temperature. In case of the fibers produced with the LIB temperature of 170 °C, initial Young's modulus of about 25 GPa and tenacity of about 800 MPa, which are equivalent to the properties for the fibers prepared in the standard high-speed spinning process of 7 to 9 km/min, were obtained at 3 to 4 km/min. On the other hand, plots of the structural and mechanical parameters against the birefringence for the LIB fibers showed a similar relation in comparison with the fibers prepared in a standard high-speed spinning process indicating that the general mechanism of fiber structure development is similar in both the spinning processes. The LIB fibers obtained in the high-speed region were found to have a large amount of β modification crystals as in the case of the common high-speed spun fibers. The amount of β form crystals in the LIB fibers increased with an increase in the take-up velocity. From these results, it was concluded that the β form crystal can be formed even at a much lower temperature than the critical temperature for the formation of β form crystals in an isotropic state, and that the formation of β form crystals can be promoted by applying a higher tensile stress in the spin-line.

High-speed Melt Spinning of PET

Abstract The high-speed spinning process of poly(ethylene terephthalate) (PET) was modified by introducing a liquid isothermal bath (LIB) which was kept at a temperature of 155°C and placed at a distance of 150 cm or 200 cm below the spinneret. The structure and mechanical properties of the as-spun fibers thus produced in the take-up speed range of 1 to 7 km/min were characterized. The results showed that the introduction of the LIB significantly influences the structural development of the as-spun fibers. The fibers produced using the LIB in the spinline showed significantly higher birefringence and crystallinity compared to the fibers produced using a standard high-speed spinning process. A semi-quantitative numerical simulation was performed with the incorporation of the LIB in the spinline to understand the mechanism of fiber structure formation during the modified high-speed spinning process of PET. The results showed that the solidification stress is considerably high when the solidification was assumed to occur at a position close to the exit of the LIB. The enhancement of molecular orientation was attributed to the increased frictional stress induced by the liquid layer whereas the spinline crystallization was found to be influenced strongly by the temperature of the liquid.