Spinneret Orifice Research Articles

Preparation and application of profiled luminescent polyester fiber with reversible photochromism materials

Abstract In this study, we realized a highly luminescent polyester fiber using a special spinneret orifice comprised of eight C-shaped pores and specific process parameters. A moderate amount of reversible photochromism materials was added along with the specific color masterbatch of suitable materials. With its high light transmittance and reflectance, the fabric has high glossiness and excellent transparency and exhibits dazzling color effects with changes in ambient light intensity. The raw materials used are polyethylene terephthalate (PET) chips with a low melting point of 110–150°C, 0.3–0.5% (active ingredient 30%) masterbatch, and 40–50% (active ingredient 50%) reversible photochromism masterbatch. The following process parameters were also chosen: for the PET chips, the drying temperature was 80–90°C, the drying time was 12–14 h, the masterbatch drying temperature was 70–80°C, the drying time was 8–10 h, the spinning temperature was 220–230°C, the cooling air temperature was 15–17°C, the cooling air speed was 0.45–0.50 m·min−1, the first hot roller temperature was 75–80°C, and the secondary hot roller had the heater turned off.

Study on pressure drop of cellulose diacetate spinning dope through regular triangular spinneret orifice

Cellulose diacetate (CDA) fiber used in cigarette tow is typically spun using a spinneret with triangular shaped cross section. The properties of the CDA fibers obtained by spinning are influenced by the interplay of various parameters, with the pressure drop being one of the most important parameters. In this paper, we have developed a pressure drop model based on the rheological information and second-type surface integrals. Meanwhile, we also experimentally determined the pressure drop of the CDA spinning dope derived from the wood pulp after pre-treatment, acetification and hydrolysis, on the basis of the differential pressure transducers mounted between the entry and exit of the spinneret with a triangular-shaped orifice. To compare the calculated and experimental results of the pressure drop, the apparent viscosity of the CDA spinning dopes with different mass concentrations was determined using a Physica MCR101 rheoviscometer. In addition, the flow rate of the spinning dopes through the orifices was determined to reveal the variations in pressure drop as a function of dope temperature, mass concentration and shearing rate. Results indicated a decrease in pressure drop with increase in dope temperature and shear rate. However, the pressure drop showed an incremental trend with flow rates or dope concentrations. The experimental data of pressure drop were in the good agreement with those calculated using the model, with deviations of less than ±8 %. The results obtained in this study can serve as a basis for understanding the various parameters controlling the spinning process.

Design of a low cost spinneret assembly for coaxial electrospinning

Coaxial electrospinning makes use of a concentric arrangement of spinneret orifices for synthesis of core-shell polymer nanofibers. Most laboratories purchase the spinneret from commercial manufacturers at a significant expense, or design it indigenously to save costs but compromise on manufacturing precision. Therefore, the present work suggests the use of a relatively lower priced McIntyre cannula needle, conventionally used for ophthalmic surgeries, as a coaxial spinneret for electrospinning. The McIntyre cannula needle was modified to synthesize hollow fibers of nylon 6, which acted as sheath with hydrogen peroxide as core during electrospinning. In addition, encapsulation of bioactives, viz., red blood cells, bacterial cells, and lysozyme (enzyme protein) was attempted, using their aqueous suspensions as core, with polycaprolactone solution as sheath. Resulting fibers had an integral core-shell structure with the bioactives encapsulated in the core. This indicated that the modified McIntyre cannula functions suitably as a spinneret for coaxial electrospinning. Thus, apart from being a clinical device, the modified McIntyre cannula needle provides an economic alternative to conventional coaxial spinneret assemblies.

Numerical investigation of the geometrical effects on UHMWPE flow characteristics in small aperture spinneret orifice

Due to high viscosity of the ultra-high molecular weight polyethylene (UHMWPE), it is difficult for the melt UHMWPE to flow through the small aperture spinneret orifice in the melt spinning forming process. The geometrical parameters of the spinneret orifice become critical to the melt spinning process. Based on the theory of polymer rheology, the finite element model of UHMWPE melt spinning had been developed by using POLYFLOW, and the length-to-diameter ratio and taper angle of the spinneret orifice effects on the UHMWPE melt flow characters were discussed. The results show that suitable length-to-diameter ratio and taper angle are helpful for the compactness and flow stability of the melt.

Luminescent polypropylene fibers containing novel organic luminescent substance

Novel organic luminescent substance (3,12-bis(dibutylamine)-7,8-dicyano-5,6,9,10-tetrahydro[5]helicene; M123) was successfully synthesized and employed to prepare luminescent polypropylene (PP/M123) fibers of different cross-sectional shapes via melt spinning. For all cross-sectional shapes (circular, hollow triangular, flat, star, and W), the PP/M123 fibers were continuously spun without fiber breakage, and possessed smooth surfaces. The designed structure of M123, containing 4 butyl groups, enabled its homogeneous mixing with hydrophobic polypropylene matrix. Addition of M123 did not alter the PP melt flow through complex spinneret orifices during fiber spinning, as evidenced by rheological measurements that melt viscosities of PP and PP/M123 at different shear rates (10–10,000 s−1) were almost identical. Results from differential scanning calorimetry also confirmed homogeneity of M123 and PP matrix as the melting temperatures and crystallinities of PP/M123 fibers were comparable to those of PP fibers. By employing organic luminescent M123, the processes of additive preparation and additive/polymer compounding were simplified, and small amount of luminescent substance as 0.05 % wt. could be used to yield effective luminescence. The PP/M123 fibers exhibited yellowish green color under normal light and emitted bright green light under ultraviolet (UV) light.

Dynamic modeling of dry-jet wet spinning of cellulose/[BMIM]Cl solution: complete deformation in the air-gap region

During the dry-jet wet spinning process of cellulose solutions with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as solvent, the special viscoelastic characteristics of the solution lead to a large air-gap distance where the extruded flow can extend completely before entering the coagulation bath. Therefore, online measurement of diameter and temperature can be carried out and the velocity on the spinning line determined reasonably. Therefore, a model of dry-jet wet spinning is proposed to simulate the extrusion and extending dynamics of cellulose/[BMIM]Cl solutions in the air-gap region with complete deformation. Material parameters such as the density and heat capacity were determined by experiment, and the heat transfer coefficient along the spin-line was evaluated by an inversion procedure involving online experimental data for temperature and diameter. A two-dimensional (2-D) approach in POLYFLOW was adopted to compute the dynamic parameters along both the axial and radial directions of the spinning line. The numerical results were verified by comparison with experimental data including temperature and diameter. It was found that the contraction flow in the spinneret orifice could not be neglected and use of a nonisothermal viscoelastic model in the constitutive equation gave better agreement between simulation and experiment.

Study on parameters influencing shape change of melt spun cross-shaped polypropylene and poly (lactic acid) fibers

Melt spinning of cross-shaped polypropylene (PP) and poly (lactic acid) (PLA) fibers was conducted to investigate influences of polymer properties and processing conditions on cross-sectional shape change in fibers. PP fibers possessed cross-shaped profile, resembling that of the original spinneret orifice, with dull edges due to die swell. Their shape factor (SF) values (1.4–1.6) were close to that of the spinneret orifice (1.7), indicating that the complex shape of the orifice could be maintained. High melt viscosity of PP, as well as its rapid crystallization, helped preventing shape change induced by surface tension. PLA fibers, on the other hand, exhibited shape change from cross to square and to round shape when spinning temperature was increased from 200 to 220 and 240 °C, respectively. Their SF values (1.1–1.2) were close to unity, indicating shape change towards circular shape. Shape deviation towards circular shape in PLA fibers was mainly driven by surface tension. Slow crystallization in PLA allowed great influence of surface tension in determining shape change of the extrudate. Increasing fiber take up speed tended to decrease SF value. Such effect was small compared to that of spinning temperature.

Simulation of contraction flow of concentrated acrylic copolymer/1-butyl-3-methylimidazolium chloride solution through spinneret orifice

The simulation of the contraction flow of concentrated acrylic copolymer/1-butyl-3-methylimidazolium chloride (P(AN-co-IA)/[BMIM]Cl) solution through spinneret orifice was carried out for the design of suitable spinneret. Geometry and mathematical models were established according to rheological behaviours and material parameters. The effects of channel geometry on variation of viscosity were simulated and discussed in detail. The numerical results show that an increase in aspect ratio resulted in the decrease in viscosity and a decrease in entrance angle may reduce the size of ‘dead’ region near the corner. From numerical investigations, the geometry with aspect ratio of 3∶1 and entrance angle of 30° was found to be suitable optimum geometry for concentrated polymer solution during dry-jet wet spinning.

The Development of the Automatic Cleaning Machine for Spinneret Orifice

The automatic cleaning requirements of spinneret orifices were analyzed. The three-dimensional positioning system for spinneret orifices cleaning, combining the XY horizontal motion platform and Z axis electric translational platform, was determined. The cleaning device of spinneret orifices was designed. The control system of automatic cleaning for spinneret orifices was developed based on Labview and the experimental analysis of the prototype was done in this paper.

Simulation on contraction flow of concentrated cellulose/1-butyl-3-methylimidazolium chloride solution through spinneret orifice

Concentrated cellulose/1-butyl-3-methylimidazolium chloride ([bmim]Cl) solution which exhibits typical elasticity has been employed to prepare fibres by dry jet wet spinning technique. In order to design the spinneret, simulation on contraction flow of cellulose/[bmim]Cl solution through spinneret orifice was carried out. Geometry and mathematical models were established according to rheological behaviour and material parameters. The effects of geometry on variation of viscosity and flow pattern were simulated and discussed. The results show that an increase in aspect ratio decreased the apparent viscosity and a decrease in entrance angle reduced the size of ‘dead’ region. The aspect ratio and entrance angle of spinneret during dry jet wet spinning were optimised.

Matrix-fibril morphology development of polypropylene/poly(butylenes terephthalate) blend fibers at different zones of melt spinning process and its relation to mechanical properties

Different shapes of dispersed phase such as sphere, laminar and fibrillar can form in the matrix phase of polymer blends. Production of blend fibers in melt spinning process can result more effective in fibrillar phase morphology formation than in other processes. In this research, the matrix-fibril morphology development during the melt spinning of polypropylene/poly(butylenes terephthalate) was studied. The shapes of blend dispersed phase collected from different zones of the melt spinning line were evaluated by scanning electron micrographs (SEM) and rheological mechanical spectra (RMS). The results showed that fibrillar shape could not be created in the PP/PBT blend fiber samples exited from the spinneret orifice (gravity spun fibers) at low contents (5 percent) of the PBT dispersed phase. However, a complete fibrillar structure was formed in all the as-spun PP/PBT blend fiber samples (melt drawn). The rheological evaluations confirmed a network structure resulting from fibril formation for the samples with high contents (20–40 %) of the PBT dispersed phase and the formation of spherical shape with low contents (5–10 %) of the PBT dispersed phase in matrix of the blend fibers. It was observed that the flow fields of processing zones and blend ratio, in producing the blend fibers, have intensive effects on morphological variations; besides there was a strong relation between the mechanical and morphological properties.

Preparation of Zirconia Fiber Body with Extrusion-Extraction Molding

Zirconia fiber body was prepared with Extrude-extracting, using zirconium slurry made of partial stabilized Zirconia ultra-fine powder. The result shows that，acetone is the first choice as extraction agent because of its notable effect of water extraction on zirconium slurry. The Zirconia fiber body, which length is over 2 centimeters and solid content is more than 98% ( weight percent ), can be prepared while the range of solid fraction in slurry is in 36 vol％～49vol％, with addition less than 1% ammonium polyacrylic acid, the extrusion force is range in 1641.5 Pa～6566.2 Pa. The solidfication mechanism transformation from slurry streamlet to fiber body is particle caking, result in water being extracted by aceton and static repulsion force falling as powder surface electronmotive force being reduced, when zirconium slurry extruded into solvent with low dielectric constant. Difference of velocity distribution of slurry passing through spinneret orifice and very small surface tension between slurry and extraction agent cause coarseness occurred on the fiber body surface.

Effects of Spinneret Orifice's Diameter and Polymer Density on Melt Blown Fabrics

Article Effects of Spinneret Orifice's Diameter and Polymer Density on Melt Blown Fabrics was published on December 1, 2010 in the journal International Journal of Nonlinear Sciences and Numerical Simulation (volume 11, issue Supplement).

Rheology in Film Processing (2)-Flow Instabilities in Film Casting Process-

Film casting is one of the important processes for obtaining the plastic film products. Molten polymer casting is conducted by cooling the extruded melts at the surface of chill roller laid below the extrusion dies. Flow instabilities in the film casting are divided into two categories. One is the shear flow instability and the other is the extensional flow instability. These instabilities are similar to those appearing in the melt spinning process. Among many parameters governing shear flow instability, shear rate and Deborah number defined as the ratio of polymer relaxation time to retention time in the land of dies or spinneret orifice are likely to be most important. The small value of Deborah number is found to be effective for depressing the shear flow instability. Regarding the extensional flow instability, draw resonance phenomena were summarized and discussed. Polymer parameters such as power low index in the power low fluid model and relaxation time in Maxwell fluid model were found to be important for onset of draw resonance instability. As process parameters, cooling effect of extruded melts, draft ratio defined as elongation ratio of melts and air gap length corresponding the distance from dies exit to chill roller were also important. Further study on transient response of disturbances having various frequencies was done. It was found that film thickness uniformity changed depending on disturbance frequency.

Descriptions of the Final Instar Larvae of Perithous septemcinctorius, Zatypota bohemani and Z. gracilis (Hymenoptera: Ichneumonidae: Pimplinae)

The exuviae of the final larval instar of three species of pimpline Ichneumonidae (Pimplinae: Delomeristini, Ephialtini), Perithous septemcinctorius (Thunberg), Zatypota bohemani (Holmgren) and Z. gracilis (Holmgren), are described. The mature larvae of Perithous Holmgren are characterized by presenting the maxillary and labial palpi with more than two sensilla. The exuviae of the different species that have been described in this genus, Perithous divinator, P. scurra and P. septemcinctorius, can be differentiated on the basis of the following characters: (a) presence/absence of spinules on the tegument, sensillum on antennal orbit, cardo; seta on posterior part of stipital sclerite; (b) presence/absence of number of setae on labrum, clypeus, maxilla, and postlabium, and sensilla on clypeus and labrum; (c) degree of development of epistoma; (d) number of sensilla of the maxillary and labial palpi (in the three species there are more than two sensilla), and (e) differentiation of the spinneret and salivary orifice. The most apparent differences between the exuviae of Zatypota Förster, Zatypota bohemani, Z. gracilis and Zatypota sp., are the expansion shown by the stipital sclerite at its lateral end and in the number, presence/absence and arrangement of the setae of the cranial sclerites (clypeus and labrum) and mouth parts (maxillae and labium). Descriptions of the cocoons of the two species of Zatypota and host records for all three species are reported.

Electro-spinning and electro-blowing of hyaluronic acid.

In this study, hyaluronic acid (HA) was electro-spun and electro-blown to prepare nonwoven nanofibrous membranes. Critical parameters for processing and corresponding effects on the membrane morphology were investigated using the methods of rheology and scanning electron microscopy (SEM). During electro-spinning, the optimal HA concentration window for nanofibrous formation was determined within a narrow range of 1.3-1.5 w/v %, corresponding to a solution viscosity range of 3-30 Pa s at a shear rate of 1 s(-1). SEM results indicated that, with increases in (1) the total concentration by blending of low molecular weight HA, (2) the evaporation rate by the addition of ethanol, and/or (3) the feeding rate of solution, the electro-spinning performance for creating nanofibers was improved. However, the improvement was not sufficient to achieve a consistent production of high quality nonwoven nanofiber membranes. This problem was overcome by a new electro-blowing process using the combination of air flow and electro-spinning. Although air blowing at room temperature around the spinneret orifice did not exhibit a remarkable enhancement of nanofiber formation of HA, the performance was significantly improved with an increase in the air blowing rate. SEM results showed that the temperature of air-blowing was the most effective parameter in ensuring HA nanofiber formation. As the temperature of the blown air increased from 25 to 57 degrees C, the nanofiber formation became consistent and uniform. A high quality HA nonwoven membrane of nanofibers was successfully produced by blowing air at 57 degrees C with a 70 ft(3)/hr flow rate.

An Analysis of Lyocell Fiber Formation as a Melt–spinning Process

In order to gain an understanding of the process of Lyocell fiber formation, the melting and solidification behaviors, heat capacity and density of cellulose N-methylmorpholine-N-oxide monohydrate (NMMO-MH) solutions were studied by differential scanning calorimetry (DSC) and dilatometry, and the diameter development of Lyocell fibers in the air gap was measured online. It was found that the Lyocell process can be considered as both a melt–spinning process in the air gap and a wet-spinning process in the coagulation bath. Cellulose chains in the solutions hindered the crystallization of NMMO-MH, and the melting point of the solutions decreased with increasing cellulose concentration. The density of cellulose NMMO-MH solutions decreased linearly with increasing temperature in the solid or the liquid state, and it increased with increasing cellulose concentration. The heat capacity of the solutions increased slightly with increasing temperature and concentration. The development of fiber diameter, the velocity gradient, and the gradient of the filaments in the air gap were limited to a short distance from the spinneret orifice. The position at which the velocity and the tensile stress gradient reached their maximum values moved closer to the spinneret orifice with increasing take-up speed.

Polyaniline spinning solutions and fibers

Polyaniline (emeraldine base form), in N-methyl-2-pyrrolidinone (NMP) at a fiber-spinnable concentration, gels so readily at room temperature that the solutions cannot be spun through spinneret orifices. Adding certain amines to the NMP solution or using certain amines as solvents provides a stable, spinnable solution. Continuous dry-jet wet spinning can be carried out with a 1,4-diaminocyclohexane/polyaniline solution. As-spun fiber is crystalline and can be oriented at high temperatures, e.g., 215°C. The drawn fibers have an average tenacity of 3.9 g/denier (gpd) (400 MPa), about five times the tenacity of the as-spun fiber. The highest electrical conductivities obtained with drawn fibers doped with aqueous H 2SO 4 and HCl were 320.5 and 157.8 S/cm, respectively. The tensile strength of the HCl-doped drawn fiber was reduced to 1.4 gpd.

Spinning rheology (2)—Analysis of melt spinning behaviors and its application

There are many rheological problems in the melt spinning process. They can be classified into two categories, i.e., the problems in shearing flow and those in extensional flow. The former is concerned with extrusion of molten PET (polyethyleneterephthalate) through spinneret orifices. Bagley’s plots showing the relationship of pressure drop to L/D of orifice were done to obtain the end correlation in the capillary flow of PET. By using this end correction values, the relaxation time of molten PET was estimated to be around 2×10−3 s under some assumptions. With regard to the problems in the extensional flow three typical and important examples were shown from both experimental and theoretical aspects. (1) Fine denier filament spinning for obtaining fibers with less than about 10 μm in diameter is a challengeable theme in the meaning of a conflict with extensional flow instability, so called draw resonance phenomenon. To solve this difficulty, it can be suggested that optimal spinneret orifice design will be required for instance. (2) High speed spinning is a process of stress‐induced crystallization of PET. Dependence of spinning behaviors such as neck‐like deformation and mechanical/structural properties on PET molecular weight was investigated. Crystallization of higher molecular weight PET was found to occur at lower spinning speed compared with that of lower one. (3) Air jet melt spinning for multifilament system was investigated both theoretically and experimentally. Computation results showed a good agreement with experimental ones in terms of the stretching speed in ejector. Birefringence values of as‐spun fibers can be estimated by using computed outputs.

Nanosecond proton pulse radiolysis

Deals with fast signal determination when the signal/noise ratio is low, and with pulse radiolysis using a jet as the target. Modifications to the nanosecond proton pulse radiolysis equipment of Burns et al. (1978) are described and discussed. Considerable improvement has been made to the method of water-jet production using spinneret orifices and a constant water flow incorporating full-flow filtering to a few microns. A magnetic field deflects the proton beam away from the water jet for approximately 15 ms every 30 ms. During this off-period a time-resolved signal of the small optical absorption of the hydrated electron is sampled. The resulting background signal is subtracted from the absorption obtained when the proton beam strikes the water jet, and successive difference signals are accumulated and stored.