Take-up Speed Research Articles

Broad poly(ethylene terephthalate) nanofiber sheet prepared by CO2 laser supersonic continuous multi-drawing

Long and broad poly(ethylene terephthalate) (PET) nanofiber sheets were fabricated by irradiation of PET fibers with a CO2 laser while drawing at supersonic velocities and continuously winding the nanofiber sheet onto a net conveyor operated at constant speed. A supersonic jet was generated by blowing air into a vacuum chamber through the fiber injection orifice. A new apparatus was developed to continuously produce broad nanofiber sheets, which was composed of a plate with eighty fiber injection orifices, a net conveyor to collect the nanofibers, a delivery roll for the isolating paper, and a take-up roll to wind the nanofiber sheet. When this apparatus equipped with an 80 zigzag orifice plate was operated at a laser power of 32.5 W, a chamber pressure of 20 kPa, a conveyor speed of 0.05 m min−1, and a take-up speed of 0.05 m min−1, a long nanofiber sheet approximately 35 cm wide and 50 μm thick could be prepared by collecting the nanofibers for 20 min. The nanofiber sheet is composed of nanofibers with an average fiber diameter of 480 nm. Continuous winding of the nanofiber sheet with this novel technique has enabled the mass production of PET nanofiber sheet.

Fabrication and characterization of hydroxylated and carboxylated multiwalled carbon nanotube/polyethersulfone (PES) nanocomposite hollow fiber membranes

Pilot scale studies were performed to investigate how CNTs might affect hollow fiber membrane (HF) resistance to stress. Further, this research explored how the addition of CNTs into membrane solutions affected trends associated with changes in conventional HF spinning parameters. Nanocomposite polymer solutions were formed by adding functionalized multiwalled carbon nanotubes (MWCNTs) (0.2wt.%, 0.4wt.% and 0.8wt.%) and PES. Membranes were fabricated under three different air residence times (1.875s, 0.935s, and 0s) by changing either the air gap (15cm or 0cm) or the fiber take-up speed (0.16m/s or 0.08m/s). Subsequently, HF membranes were characterized according to their porosity, permeability, contact angle, and tensile strength. As expected, stress resistance and Young's Modulus increased up to 125% and 118% for certain membranes containing CNTs, respectively. Shorter air residence times caused significant porosity increases and large permeability decreases in the membranes containing CNTs. Finally, the effect of the de-mixing rate was more pronounced in nanocomposite membranes, while the effect of take-up speed was more pronounced in pristine membranes. This study establishes the potential for CNTs to improve the mechanical properties of HF membranes, and serves as the first demonstration of industrial-scale production of CNT-polymer HF membranes.

New Features of Silver/Zinc Loaded Nanocomposite Textiles; Dyeability, Abrasion Resistance and Comfort

This paper investigates the effect of nanoparticles on some new features of silver/zinc loaded nanocomposite fabrics. These fabrics have been fabricated from continuous nanocomposite multifilament yarns produced on a pilot plant melt spinning process with the take-up speed of 2000 m.min-1. According to the results, the dyeability of nanocomposite fabrics with acidic dyes increased as compared to the pure PP. The electrostatic interaction between negatively charged group of acidic dye molecules and positively charged silver nanoparticles can improve dyeability. The results indicated close relationship between the abrasion resistance of fabrics and tensile properties of produced yarns including tenacity, modulus, and rupture work. The results also showed the increasing of the water vapor permeability at temperatures above 25 oC and decreasing permeability at temperatures below 25 oC for nanocomposite fabrics containing 0.1 wt% silver/zinc. This simplifies removing of body heat and sweat and consequently offers more comfort for garment, tent, curtain, etc. at temperatures above 25oC. On the other hand, lower vapor permeability at a low temperature protects the body from cool weather through preventing loss of the body heat and weather flow. This nanocomposite fabric can smartly adapt the permeability with human body requirements by changing the environment temperatures.

Production of mixed matrix hollow fiber membrane for CO2/CH4 separation

Studies on mixed matrix membrane (MMM) have been sprouting rapidly since the last few decades, but mostly fabricated in the form of dense, flat films. In this work, hollow fiber Polysulfone (PSF)-Cloisite®15A (C15A) MMM were produced using our in-house hollow fiber spinning machine. Various spinning parameters are at play in order to ensure the formation of defect-free high performance hollow fiber. Spinning process parameters such as dry gap height, force convection rate, dope extrusion rate, and take-up speed have been systematically studied in order to identify the optimum fabrication conditions. Extensive characterizations on the membrane morphology, membrane surface properties, polymer d-spacing and gas separation performance were conducted using SEM, AFM, XRD, and pure gas permeation experiment. The appropriate balance between dry-gap residence time and force convective rate is essential to yield membrane with good permeability–selectivity combinations. CO2 permeance was increased from 17.39 to 56.25×10−6cm3(STP)/cm2scmHg when the dope extrusion rate was increased from 1.5cm3/min to the optimum extrusion rate of 2.5cm3/min. Membranes spun at high collection speed (up to 35m/min) exhibited practically attractive fiber geometry comparable to commercial hollow fibers (∼300μm diameter) but the permeation properties were rather disappointing which might be caused by excessive deformation of polymer chain due to stretching. Hollow fiber MMM containing layered organoclay has exhibited excellent CO2/CH4 pure gas selectivity of 40.26%, 46% higher than that of pristine hollow fiber fabricated under the same optimized conditions without compromising the CO2 flux. The MMM was also found to be more thermally and mechanically robust in comparison to its neat counterpart.

Effects of coagulation bath temperature on structure and performance of poly (vinyl butyral) hollow fiber membranes via thermally induced phase separation

Poly (vinyl butyral) (PVB) hollow fiber membranes were fabricated via thermally induced phase separation (TIPS). The effects of coagulation bath temperature (CBT) on the structure and performance of membranes were investigated in detail. The morphologies of the membranes were studied by scanning electron microscopy (SEM), the performances of water permeability, rejection, breaking strength and elongation were measured, respectively. The results indicate that all the membranes have the asymmetric morphology and the thickness of the skin layer decreases and the pore size of the outer layer increases with the increase of CBT. The permeability of membranes prepared at air gap 1.0 cm and take-up speed 0.253 m/s increases from 1.047×10−7 to 5.909×10−7 m3/(m2·s·kPa) with the CBT increasing from 20 °C to 40 °C, and sharply increases to 35.226×10−7 m3/(m2·s·kPa) once the CBT arrives at 50 °C. While the carbonic ink rejections have no significant decrease, totally exceed 98%, but that of acid-maleic acid copolymer greatly decreases with the increase of CBT. Both the breaking strength and elongation decrease with the increase of CBT.

Excellent bonding behaviour of novel surface-tailored fibre composite rods with cementitious matrix

Novel composite rods were produced by a special braiding technique that involves braiding of polyester yarns around a core of resin-impregnated carbon fibres and subsequent curing. The surface roughness of these braided rods was tailored by replacing one or two simple yarns in the outer-braided layer with braided yarns (produced from 8 simple yarns) and adjusting the take-up velocity. Pull-out tests were carried out to characterize the bond behaviour of these composite rods with cementitious matrix. It was observed that the rod produced with two braided yarns in the outer cover and highest take-up speed was ruptured completely before pull-out, leading to full utilization of its tensile strength, and exhibited 134% higher pull-out force as compared to the rods produced using only simple braiding yarns.

Synergistic action of non-solvent induced phase separation in preparation of poly(vinyl butyral) hollow fiber membrane via thermally induced phase separation

A systematic study of air gap distance effects on the structure and properties of poly(vinyl butyral) hollow fiber membrane via thermally induced phase separation (TIPS) has been carried out. The results show that the hollow fiber membrane prepared at air gap zero has no skin layer; the pore size near the outer surface is larger than that near the inner surface; and the special pore channel-like structure near the outer surface is formed, which is quite different with the typical sponge-like structure caused by TIPS and the finger-like structure caused by non-solvent induced phase separation (NIPS), because of the synergistic action of non-solvent induced phase separation at air gap zero. The pore size gradually decreases from outer surface layer to the intermediate layer, but increases gradually from intermediate layer to the inner surface layer. With the increase of air gap distance, the pore size near the outer surface gets smaller and a dense skin layer is formed, and the pore size gradually increases from the outer surface layer to the inner surface layer. Water permeability of the hollow fiber membrane decreases with air gap distance, the water permeability decreases sharply from 45.50×10−7 to 4.52×10−7 m3/(m2·s·kPa) as air gap increases from 0 to 10 mm at take-up speed of 0.236 m/s, further decreases from 4.52×10−7 to 1.00×10−8 m3/(m2·s·kPa) as the air gap increases from 10 to 40 mm. Both the breaking strength and the elongation increase with the increase of air gap distance. The breaking strength increases from 2.25 MPa to 4.19 MPa and the elongation increases from 33.9% to 132.6% as air gap increases from 0 mm to 40 mm at take-up speed 0.236 m/s.

Effect of annealing on the morphology of porous polypropylene hollow fiber membranes

Three different polypropylene resins were selected to develop microporous membranes through melt spinning, annealing and stretching. The effects of take-up speed, cooling rate, stretching, and annealing temperature on the crystalline structure and orientation of the membrane were investigated using field emission scanning electron microscopy. An annealing process was employed to generate and enlarge the pores and lamellar structure, and improved the crystallinity of hollow fiber precursors, before the stretching process. The annealed hollow fiber precursor was stretched by cold, hot, and cold/hot complex stretching. We observed that porous structure on the outer and inner surfaces of the stretched precursor fibers were produced by cold and hot complex stretching.

Circular braiding take-up speed generation using inverse kinematics

Circular overbraiding of composite preforms on complex mandrels currently lacks automatic generation of machine control data. To solve this limitation, an inverse kinematics-based procedure was designed and implemented for circular braiding machines with optional guide rings, resulting in a take-up speed profile for a given braid angle distribution on mandrels with complex 3D shapes including non-axisymmetric, optionally eccentric cross-sections that can vary in shape and size along an optionally curved mandrel centerline, allowing a curved machine movement. This procedure reduces the problem size, resulting in a short computation time, fit for CAE process chain integration. Numerical control data was generated for a complex mandrel with a specified braid angle and a triaxial braid. A simulation using this control data yields a braid angle that deviates a few degrees from the specified braid angle. The simulation was validated experimentally, using the generated instructions to control the braiding machine. This showed a deviation from the simulated braid angle of 3 degrees in the centered, non-tapered mandrel regions, up to 10 degrees in tapered regions and an experimental scatter of 7 degrees. The deviation is mainly attributed to the neglect of yarn interaction and guide ring contact friction in the model, leading to an incorrectly modeled convergence zone length.

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.

Air-gap spinning of cellulose/ionic liquid solution and its characterization

In order to study the effects of the spinning conditions on the structure and the properties of the regenerated fiber, cellulose was dissolved in ionic liquid and then spun into fiber using an air-gap spinning process. The solution concentration, the take-up speed and the fixation of the fiber ends during coagulation improved the crystallinity and the tensile strength at the same time. The fiber surface became smooth by addition of DMF (dimethylformamide). However, it decreased the crystallinity and the tensile strength of the fibers. We revealed that the developed structure during coagulation determined the morphology and the properties of the fibers. The co-solvent resulted in smooth surface of the fiber and also changed the mechanical properties.

탄소나노튜브 및 그래핀 나노플레이트 폴리프로필렌 복합재 필름 압출 및 물성 평가

본 연구에서는 폴리프로필렌과 다양한 탄소나노소재를 사용하여 제조한 복합재의 압출방향 및 권취속도에 따른 기계적 물성과 결정화도에 대한 연구를 수행하였다. 폴리프로필렌에 탄소나노소재를 균일하게 분산시키기 위해 미분쇄기에 폴리프로필렌 분말(<700 <TEX>${\mu}m$</TEX>)과 탄소나노소재를 혼합한 후 나노복합재 필름 제조를 위해 압출기를 사용하였다. 나노복합재 필름의 결정화도를 분석하기 위해 differential scanning calorimetry를 이용하였다. 기계적 물성을 인장시험을 통해서 측정한 후 순수 폴리프로필렌 물성과 비교하였고, 압출 시 필름 권취속도에 대한 나노복합재 결정화도의 차이를 확인하였다. 탄소나노소재를 첨가함으로써 고분자 필름의 기계적 물성이 향상됨을 확인하였고, 그에 따른 결정화도 역시 증가하는 것을 확인하였다. 반면, 권취속도가 증가 할수록 압출물의 냉각속도도 역시 증가함으로써 결정화도가 오히려 감소함을 확인하였다. Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of <TEX>$750m^2/g$</TEX> showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.

Melt-spinning basalt fibers based on dielectric heating and steady-state process characteristics

In this study, we introduce a new melt-spinning technology for producing basalt fibers on a laboratory scale and provide a dynamic model describing the basalt-fiber spinning process with the thermal effect in terms of an Arrhenius equation. The new trial system for basalt melt-spinning was established, while a microwave furnace was used to melt the quarried basalt rocks. And a susceptor, i.e., silicon carbide (SiC) was applied. A crucible with a one-hole bushing took the role of the spinning block, which was placed in the heating zone. A take-up device controlled by a PC was installed and the take-up speed was varied in order to investigate the fiber drawing effect on the thickness produced. Experimental results demonstrated that this new system is feasible for producing basalt fibers. The theoretical estimate of the fiber diameter profile with the Arrhenius viscosity description along the spinning line agreed well with the measurement. The diameter profile of the basalt fibers decreased with a funnel-shaped profile along the spinning line, while it changed very rapidly near the bushing hole up to the position 15 mm downwards, and then the fiber diameter decreased further up to the position 30 mm. In the remaining spinning zone the diameter reduction was very small. The gravitational effect of the molten basalt in the crucible on the fiber diameter was negligible.

기격 습식 방사를 이용한 면 린터 기반 셀룰로스 재생 섬유 제조 및 평가

Compared to the conventional viscose rayon process, Lyocell process using NMMO as a solvent provides a naturally-friendly, less toxic, relatively simple method for producing regenerated cellulose fiber with excellent properties. Existing wood pulp based Lyocell, however, shows some disadvantages such as forest destruction. So, in this study, a novel regenerated cellulose fiber, cotton linter based Lyocell, was prepared by dry jet-wet spinning with a lab scale equipment changing concentration of cellulose/NMMO solution, take-up speed, etc, which are strongly related with fiber properties and its properties were compared with wood pulp based Lyocell fiber. The tenacity and strain at break of the resultant fibers were correlated with the intrinsic fiber properties such as birefringence, crystallinity, and crystalline orientation index.

The microstructures of extrusion cast biodegradable poly(butylene succinate) films investigated by X-ray diffraction

Cast films of poly(butylene succinate) (PBS) were prepared by extrusion followed by stretching using a chill roll. The effects of extrusion temperature and take-up speed on the microstructures of the PBS cast films were investigated by two-dimensional wide angle X-ray diffraction (2D-WAXD) and small angle X-ray scattering (2D-SAXS) techniques. It was found that the processing conditions had almost no influence on the degree of crystallinity and the long period of the lamellae of the films, whereas the orientations at both crystal and lamellar levels increased with increasing take-up speed and decreasing extrusion temperature. In addition, the 2D-SAXS patterns revealed the formation of the shish-kebab structure at a lower extrusion temperature and higher take-up speed.

Design and fabrication of lotus-root-like multi-bore hollow fiber membrane for direct contact membrane distillation

Highly constrained by the requirements of high porosity and large pore sizes, traditional single-bore hollow fiber membranes often suffer from easy breakage and performance instability during long-term operations of membrane distillation (MD). In this work, a multi-bore PVDF hollow fiber (MBF) membrane with a lotus root-like geometry was designed and successfully fabricated via the specially designed spinneret and optimized spinning conditions. Various effects of spinning parameters including bore flowrate, dope flowrate and take-up speed were investigated on the membrane macro- and micro-structure, mechanical properties and direct contact membrane distillation (DCMD) performance. The tensile strength characterizations have proven the excellent mechanical rigidity and elasticity of MBF membranes. Even for the MBF membrane with a thin wall of around 40μm, the maximum load was as high as 2.4N. Most importantly, the performance of the DCMD of the MBF membrane was only slightly lower or even comparable to that of single-bore membranes. In addition, the MBF membranes exhibited superior stability in terms of vapor permeation flux and salt rejection during the continuous DCMD experiment with robust operational conditions. We believe this work may have profound implication to the development of mechanically durable membranes not only for membrane distillation MD but also for other membrane applications.

Fabrication and characterization of silk braided sutures

Silk sutures are already used in surgery. Silk is a natural protein fiber and easily prone to microbial infection hence we have developed novel antimicrobial silk braided sutures. Braided silk sutures were fabricated using a circular braiding machine with a 16 carrier arrangement normally used to produce braided structures. The same structure was used to manufacture braids with three different take-up speed levels obtained by changing the cogwheel ratio on the braiding machine. The influence of braid angle, test parameters such as gauge length and extension rate on tenacity and knot strength of braided silk sutures were studied. Silk sutures fabricated at higher braid angle, tested at shorter gauge length and greater test speed showed lower values of tenacity and knot strength. Chitosan was applied on braided silk sutures to impart antimicrobial characteristics. The Scanning electron microscopy study reveals the absence and presence of chitosan on the surface of untreated and treated sutures respectively. The antimicrobial properties of chitosan and tetracycline hydrochloride drug were tested using Agar diffusion method SN 195920 both when applied independently and collectively on silk sutures against Escherichia coli and Staphylococcus aureus. The combined antimicrobial effect of chitosan and tetracycline hydrochloride drug is very good and can be used to develop antimicrobial silk sutures for providing protection against microbial infections.

Solvent-free fabrication of three dimensionally aligned polycaprolactone microfibers for engineering of anisotropic tissues

Fabrication of aligned microfiber scaffolds is critical in successful engineering of anisotropic tissues such as tendon, ligaments and nerves. Conventionally, aligned microfiber scaffolds are two dimensional and predominantly fabricated by electrospinning which is solvent dependent. In this paper, we report a novel technique, named microfiber melt drawing, to fabricate a bundle of three dimensionally aligned polycaprolactone microfibers without using any organic solvent. This technique is simple yet effective. It has been demonstrated that polycaprolactone microfibers of 10μm fiber diameter can be directly drawn from a 2mm orifice. Orifice diameter, temperature and take-up speed significantly influence the final linear density and fiber diameter of the microfibers. Mechanical test suggests that mechanical properties such as stiffness and breaking force of microfiber bundles can be easily adjusted by the number of fibers. In vitro study shows that these microfibers are able to support the proliferation of human dermal fibroblasts over 7days. In vivo result of Achilles tendon repair in a rabbit model shows that the microfibers were highly infiltrated by tendon tissue as early as in 1month, besides, the repaired tendon have a well-aligned tissue structure under the guidance of aligned microfibers. However whether these three dimensionally aligned microfibers can induce three dimensionally aligned cells remains inconclusive.

CFD modeling of the melt spinning of poly (ethylene terepthalate) at low take-up velocities

In this study, a model was formulated to describe the melt spinning of Poly (ethylene terepthalate) (PET) at different quench air speeds and temperatures, mass throughputs and a low range of take-up velocities. The constitutive equations of the Newtonian model were used for modeling, which assumed the flow of polymer was viscous. To simulate the influence of the process parameters on the melt spinning process, a fiber model was used and coupled with computational fluid dynamics (CFD) calculations of the quench air flow. In the fiber model, energy, momentum and mass balance were solved for the polymer mass flow. The formulation was implemented in the Fluent Continuous Fiber Model. Numerical predictions of the model were compared with experimental data reported in the literature for PET. The take up speed, mass throughput and the temperature of melt spinning were the primary parameters of final fiber properties for both simulation and experimental results. In the simulation results, the effects of take-up speed and mass throughputs were clearly different at high take-up velocities and low mass throughputs because of viscoelastic behavior of polymers in the melt spinning. The Newtonian model was more reasonable for lower take-up speeds and higher mass throughputs. Key words: Melt spinning, poly (ethylene terepthalate), modeling, process parameters.

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.