Preparation of form-stable silica/polyethylene glycol composites using flash-drying for large-scale melt-spun fibers with thermal management property

The combination of phase change materials (PCMs) with fibers can afford smart fibers with thermal management properties. However, the issues of easy leakage and poor thermal stability of PCMs often limit their use in high-temperature spinning. Herein, we report a form-stable PCM of spherical SiO₂/PEG composite that was prepared through flash-drying using inorganic dendritic silica (D-SiO₂) as the core skeleton to support organic polyethylene glycol (PEG). The SiO₂/PEG composite not only presents high crystallization enthalpy (101.35 J/g), but also maintains a superior phase change stability. Meanwhile, it exhibits a significant temperature hysteresis effect during heating and cooling, and the endothermic and exothermic time are 381.95 and 293.57 s, respectively. Because the degradation temperature of 300°C for SiO₂/PEG is higher than the melt processing temperature of 240–270°C for the preparation of polyamide 6 (PA6) fibers, PA6/SiO₂/PEG fibers were prepared using melt spinning. The prepared PA6/SiO₂/PEG fibers exhibit high latent heat (17.14 J/g), outstanding thermal cycling stability and satisfactory temperature adjustment properties, and the temperature-adjustment time of 458.97 s and temperature difference of 10.68°C under the thermal environment. Moreover, the tensile strength of PCFs-20% reached 1.97 cN/dtex after drawing, which make PCFs meet the requirements of uses in textile industries.     

聚酰胺6蓄热调温纤维的制备与表征

以聚乙二醇为储能调温介质,通过多孔纳米材料吸附制备了形态稳定的相变材料(PCMS),然后以聚酰胺6(PA6)为基体,采用熔融共混纺丝制备了蓄热调温PA6纤维。通过场发射扫描电子显微镜、差示扫描量热仪、热重分析仪、粉末X射线衍射仪表征了纤维的结构和性能。研究表明:熔纺PA6/PCMs纤维储能调温焓值达到19.01 J/g,预期可在航空服、军用作战服和民用服装等领域获得很好的应用。     

Design and fabrication of flexible mesoporous Si-doped Al2O3 ultrafine fibers by electro-blow spinning (EBS) technique

In this paper, flexible mesoporous Si-doped Al₂O₃ ultrafine fibers were successfully prepared by electro-blow spinning (EBS) technology followed by a calcination process. The effects of spinning parameters, including air pressure, voltage, and solution injection rate on the morphology and diameter of fibers were investigated. The results showed that the spinning parameters played a key role on determining the morphology and diameter of fibers, and the specific surface area of fibers significantly increased with the increasing content of pore forming agents (polytetrafluoroethylene, PTFE), at the same time the pore size distribution was mainly concentrated at ~5 nm. Most importantly, Si(OC₂H₅)₄ was introduced to act as the flexible regulator which could inhibit the growth of alumina crystal, decrease the crystal size, and thus the flexibility of obtained mesoporous Si-doped Al₂O₃ ultrafine fibers can be improved. Moreover, the fibers productivity by EBS method was higher than that of traditional electro-spinning. In the future, the mesoporous Si-doped Al₂O₃ ultrafine fibers may perform desired function and spread their applications in different areas.     

Preparation and performances of poly(phthalazinone ether sulfone ketone) hollow fiber membranes with excellent thermotolerance

The cloud points of PPESK/NMP/H₂O ternary system at different temperatures were measured by titrimetric method. The binodal lines in the ternary phase diagram of the poly(phthalazinone ether sulfone ketone (PPESK) dope system was determined, on the basis of the cloud point experimental data being linearly fitted with the semiempirical linear cloud point correlation. Furthermore, phase separation behavior during the phase inversion of PPESK membrane‐forming system was discussed in terms of the phase diagram. Then, dry–wet spinning technique was employed in manufacturing PPESK hollow fiber membranes by immersion precipitation method. The cross‐section morphologies of hollow fibers were observed by scanning electronic microscopy. Also, the effects of dope solution composition and spinning parameters, including the coagulant composition and the spinning temperature on the separation performances of fibers, were evaluated by permeability measurements. The thermotolerance of the PPESK hollow fiber membranes prepared in the work was examined for the permeation operation at different temperatures and pressure differences. The experimental results showed that pure water flux increases several fold along with the temperature increases from 20 to 80°C at different operation pressures, while the solute rejection only decreases slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 878–884, 2006     

Hydraulic resistance of a deformable layer of fibrous material

Filtration of spinning solutions, spinning bath, and finishing solutions through a layer of fibrous material is widely used in different chemical fiber plants. In finishing of textile fibers on spools and cakes, the liquid is filtered through a layer of fiber attached by winding. At the same time, filtration is through a layer of unattached, freely packed fibrous material with random orientation of the individual fibers or through layers of nonwoven material in filtration on filters with a metal — gauze — asbestos gravity layer, in fiber finishing or modification processes, and in processes involving ion-exchange, chemisorption, and catalytically active fibrous materials.Moscow State Textile Academy. Translated from Khimicheskie Volokna, Vol. 25, No. 1, pp. 13–15, January–February, 1993.     

An eco-friendly procedure for achieving high-yield carrageenan from Hypnea cervicornis suitable for wet spinning

In this study, an eco-friendly method was proposed to prepare carrageenan suitable for spinning into fibers. The extract from Hypnea cervicornis without alkali pretreatment was directly converted into the spinning solution, and carrageenan fibers were obtained via wet spinning. The improved procedure had a higher yield (61.8% ± 1.1%) than the traditional method (36.0% ± 1.3%). The chemical structure of the carrageenan was analyzed via fourier transform infrared spectroscopy (FTIR) and carbon nuclear magnetic resonance spectroscopy (¹³C NMR). It was confirmed that carrageenan extracted from Hypnea cervicornis was mainly ι-carrageenan and its structure was not changed by alkali pretreatment. The properties of the spinning solution and fibers were characterized using dynamic light scattering (DLS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and tensile tests. The results showed that the spinning solution prepared by the improved procedure was homogeneous and suitable for spinning, and the mechanical strength of the novel prepared carrageenan fibers was equal to the fibers spanned from traditional carrageenan.     

Catalytic gasification of doped carbon — a microscopic study

Inorganic additives in carbons are often active, catalytically, during its gasification. The method of addition, particle size, chemical composition and subsequent heattreatment of the additives control their relative efficacies. There are difficulties in attempts to reproduce these efficacies. To overcome these problems, carbons have been prepared by carbonisation of the polymer prepared from furfuryl alcohol containing known concentrations of soluble additives. The resultant carbons contain atomic dispersions of metals in a manner analogous to doped semi-conductors. Such dispersions are catalytically active to gasification by CO₂, N₂O and O₂. Topographical changes produced on gasification are followed by scanning electron microscopy. Rarely, if ever, does the gasification proceed evenly over the entire surface. The resultant pitting can influence structural and adsorptive properties of commercial carbons, subject to gasification, i.e. parent materials for active carbons and cokes. Results indicate that diffusion of the catalytically active metal into carbon from catalytic material added in particulate form may be a significant stage in the mechanism of catalytic gasifications.     

Fabrication and characterization of melamine formaldehyde fibers with enhanced mechanical properties and high fire resistance by dry spinning

High-performance melamine formaldehyde (MF) fibers are successfully produced by innovatively utilizing dry spinning with high efficiency and low emission. Three ways are adopted to enhance the mechanical performance of MF fiber. First, MF resin is modified by introducing flexible chain segments into MF three-dimensional network and reducing the network crosslink density. Second, the energy dissipation capacity of the MF fibers is improved through constructing of hydrogen bond networks among modified MF resin, nano-SiO₂, and/or polyvinyl alcohol and forming interpenetrating network structures of modified MF resin and nano-SiO₂. Third, homogeneous and stable spinning solutions without phase separation are prepared, which can reduce interior defects of MF fibers. The chemical changes in the spinning solutions with increasing temperature and the rheology behavior of the solutions are investigated. In addition, the effects of fiber compositions on microstructure, morphology, and the properties of the MF fibers are also systematically studied. The prepared MF fibers possess high fire retardancy (i.e., limiting oxygen index >40%), thermal stability (i.e., T_max >360°C), and mechanical properties (i.e., tensile strength >2.5 cN/dtex).     

PA6/LDPE/PE-g-MAH共混纳米纤维的制备及结构研究

采用共混海岛纺丝法制备聚酰胺6/低密度聚乙烯/聚乙烯接枝马来酸酐(PA6/LDPE/PE-g-MAH)共混纤维,溶解剥离出LDPE基体相,可制备出PA6纳米纤维;研究了共混物的组成和纺丝条件对共混纤维的相结构、结晶、力学性能及PA6纳米纤维直径的影响。结果表明:随着共混物中PA6分散相含量增加,PA6纳米纤维的直径逐渐增大;PA6质量分数从30%增加至60%时,PA6纳米纤维平均直径由107 nm增至149nm;PA6质量分数为70%时,由于相逆转无法得到PA6纳米纤维;在PA6质量分数为55%条件下,提高拉伸倍数,PA6纳米纤维的直径进一步降低,且结晶度、力学性能增加。     

莫来石纺丝溶胶的流变特性及可纺性研究

本文以氢氧化铝为铝源,以硅溶胶为硅源,采用溶胶-凝胶技术制备了莫来石纺丝溶胶,采用稳态及动态两种测试模式,研究了纺丝溶胶的粘度及流变性能,并采用干法纺丝制备连续莫来石凝胶纤维,评价了溶胶的可纺性。结果表明,温度对溶胶的非牛顿指数及结构粘度指数影响不大,这将有利于纺丝工艺的调节;高固含量有利于莫来石凝胶纤维的纺丝成纤,制备的凝胶纤维更细,纺丝稳定性更好。     

蓄热调温聚丙烯腈纤维的制备及性能研究

将石蜡相变微胶囊(MEPCM)添加到聚丙烯腈(PAN)的硫氰酸钠纺丝液中,通过湿法纺丝制备了蓄热调温PAN纤维,考察了MEPCM质量分数对纺丝液可纺性和纤维力学性能、热学性能及染色性能的影响。结果表明:随着MEPCM质量分数的增加,纺丝液表观黏度下降,PAN纤维的蓄热调温能力增大,纤度增大,密度减小,断裂强度和断裂伸长率下降,热分解温度略有降低;对阳离子红5GN的恒温染色速率常数增大,平衡上染量减小,半染时间缩短。     

Stability and spinnability of modified melamine–formaldehyde resin solution for centrifugal spinning

Melamine microfibers were first prepared by centrifugal spinning. The stability and spinnability of a melamine–formaldehyde (MF) resin solution were improved as expected by adding various modifier combinations. Considering the storage stability of solutions characterized by visual inspection, turbidity tests, and viscosity measurements and combined with the fiber morphology, the optimal modifier combination was obtained. The spun fibers manifested a good morphology and thermal stability as measured by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Moreover, microfibers prepared by three spinning methods (centrifugal spinning, electrospinning, and centrifugal electrostatic spinning) were compared to choose the suitable spinning method for different fields in the future. This work provides systematic and scientific guidance on the synthesis of MF resin solutions and rapid mass production of melamine microfibers and also demonstrates that centrifugal spinning of melamine microfiber is a promising candidate for flame retardance and CO₂ adsorption at elevated temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46072.     

Preparation and properties of polyamide 6 fibers prepared by the gel spinning method

Polyamide 6 (PA6) fibers were prepared by CaCl₂ complexation and the gel spinning technique. PA6 was partially complexed with CaCl₂ for the purpose of suppressing interchain amide group hydrogen bonding. The fibers were characterized with scanning electron microscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. In the gel spinning process, a mixed tetrachloroethane and chloroform solution was chosen as the coagulation bath after a comparison of different types of solutions. From our investigation of the morphology, structure, and mechanical properties of gel‐spun and hot‐drawn fibers, it was indicated that the modulus and tensile strength increased with increasing draw ratio, the orientation of the fibers was improved, and the cross section of the PA6 gel fibers became more smooth and tight. The results from the XRD, DSC, and FTIR tests indicated that calcium metal cations complexed with the carbonyl oxygen atoms of PA6. The maximum modulus and tensile strength values obtained in this study were 28.8 GPa and 413 MPa, respectively, at a draw ratio of 8. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structural and thermal property changes of plasticized spinning polyacrylonitrile fibers under different spinning speeds

The effect of the spinning speed on structural and thermal properties of polyacrylonitrile (PAN) fibers prepared by plasticized spinning was investigated. The PAN fibers were characterized by scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. We found that the surface morphology of the fibers was relatively smooth. The presence of a small amount of surface defects was caused by the instability of spinning process. The final fibers may have had two tensile fracture modes, that is, cluster breaking and axial split fracture. The structure of the as‐spun fibers was destroyed when the spinning speed was up to 500 m/min; this led to chain scission in the amorphous region. The final fibers exhibited mechanical properties that were roughly comparable to those of commercial PAN fibers. The changing trend in the cyclization temperature of the final fibers was consistent with that of crystallinity, which first increased and then decreased. The decomposition temperature in the amorphous region increased with increasing spinning speed. The decomposition temperature in the crystalline region increased with increasing crystallinity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45267.     

Rheological behavior of polyester blend and mechanical properties of the polypropylene–polyester blend fibers

The article deals with method of preparation, rheological properties, phase structure, and morphology of binary blend of poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) and ternary blends of polypropylene (PP)/(PET/PBT). The ternary blend of PET/PBT (PES) containing 30 wt % of PP is used as a final polymer additive (FPA) for blending with PP and subsequent spinning. In addition commercial montane (polyester) wax Licowax E (LiE) was used as a compatibilizer for spinning process enhancement. The PP/PES blend fibers containing 8 wt % of polyester as dispersed phase were prepared in a two‐step procedure: preparation of FPA using laboratory twin‐screw extruder and spinning of the PP/PES blend fibers after blending PP and FPA, using a laboratory spinning equipment. DSC analysis was used for investigation of the phase structure of the PES components and selected blends. Finally, the mechanical properties of the blend fibers were analyzed. It has been found that viscosity of the PET/PBT blends is strongly influenced by the presence of the major component. In addition, the major component suppresses crystallinity of the minor component phase up to a concentration of 30 wt %. PBT as major component in dispersed PES phase increases viscosity of the PET/PBT blend melts and increases the tensile strength of the PP/PES blend fibers. The impact of the compatibilizer on the uniformity of phase dispersion of PP/PES blend fibers was demonstrated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4222–4227, 2006     

New class of cellulose fiber spun from the novel solution of cellulose by wet spinning method

A novel cellulose solution, prepared by dissolving an alkali-soluble cellulose, which was obtained by the steam explosion treatment on almost pure natural cellulose (soft wood pulp), into the aqueous sodium hydroxide solution with specific concentration (9.1 wt %) was employed for the first time to prepare a new class of multifilament-type cellulose fiber. For this purpose a wet spinning system with acid coagulation bath was applied. The mechanical properties and structural characteristics of the resulting cellulose fibers were compared with those of regenerated cellulose fibers such as viscose rayon and cuprammonium rayon commercially available. X-ray analysis shows that the new cellulose fiber is crystallographically cellulose II, and its crystallinity is higher but its crystalline orientation is slightly lower than those of other commercial regenerated fibers. The degree of breakdown of intramolecular hydrogen bond at C₃[X_am(C₃)] of the cellulose fiber, as determined by solid-state cross-polarization magic-angle sample spinning (CP/MAS) ¹³C NMR, is much lower than other, and the NMR spectra of its dry and wet state were significantly different from each other, indicating that cellulose molecules in the new cellulose fiber are quite mobile when wet. This phenomenon has not been reported for so-called regenerated cellulose fibers.     

The index of dry‐jet wet spinning for polyacrylonitrile precursor fibers

A new spinning index for a PAN precursor fiber is proposed that includes the viscosity of a spinning dope, the thermodynamic affinity, and the draw ratio during the spinning process. Through dry‐jet wet spinning, six types of PAN precursor fibers with different spinning parameters, including solid content, solvent content in a bath, and draw ratio, were fabricated and analyzed with tensile tests, SEM, and XRD. The results show that the spinning index can reflect the mechanical properties of the fibers but is less indicative of crystallinity. Hence, the current spinning index is recommended for use as an indicator for the mechanical properties of PAN precursor fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41265.     

Effect of processing parameters of the continuous wet spinning system on the crystal phase of PVDF fibers

Poly(vinylidene difluoride) (PVDF) has been widely used in piezoelectric applications as films and nanofiber mats, but there are limited publications on piezoelectric wet‐spun fibers. In this work, PVDF fibers were prepared using the wet spinning method, and the processing parameters, including the drawing ratio and heat setting temperature, were controlled in the continuous wet spinning system to increase the β‐phase crystallinity of the fibers. In addition, the wet‐spun PVDF fibers were compressed by a rolling press to eliminate voids in the fibers. Then, the compressed PVDF fibers were poled to align the molecular dipoles. The crystal structures of the PVDF fibers were investigated using X‐ray diffraction and Fourier‐transform infrared spectroscopy. Single filament tensile tests were performed to measure the tensile strength of the fibers. The morphologies of the PVDF fibers with respect to the processing parameters were observed by scanning electron microscope (SEM) and polarization optical microscopy. The piezoelectric constant of the prepared PVDF fibers was then measured using a d₃₃ meter. The wet‐spun PVDF fibers showed the highest β‐phase and piezoelectric constants when the drawing ratio and heat setting temperature were 6 and 150 °C, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45712.     

High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions

High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ～1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551.     

PEEKWC ultrafiltration hollow‐fiber membranes: Preparation,morphology, and transport properties

A series of hollow‐fiber membranes was produced by the dry–wet spinning method from PEEKWC, a modified poly(ether ether ketone) with good mechanical, thermal, and chemical resistance. The fibers were prepared under different spinning conditions, varying the following spinning parameters: polymer concentration in the spinning solution, height of the air gap, and bore fluid composition. The effect of these parameters on the water permeability, the rejection of macromolecules (using dextrane with an average molecular weight of 68,800 g/mol), and the morphology of the membranes was studied. The results were also correlated to the viscosity of the spinning solution and to the ternary polymer/solvent/nonsolvent phase diagram. The morphology of the cross section and internal and external surfaces of the hollow fibers were analyzed using scanning electron microscopy (SEM). All membranes were shown to have a fingerlike void structure and a skin layer, depending on the spinning conditions, varying from (apparently) dense to porous. Pore size measurements by the bubble‐point method showed maximum pore sizes ranging from 0.3 to 2 μm. Permeability varied from 300 to 1000 L/(h^?1 m^?2 bar) and rejection to the dextrane from 10 to 78%. The viscosity of polymer solutions was in the range of 0.2 to 3.5 Pa s. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 841–853, 2004