Excellent Spinnability Research Articles

Evaluating the Hydrothermal Stability of Superbase-Based Ionic Liquids in Cellulose Fiber Spinning.

This study highlights the substantially improved hydrothermal stability of 7-methyl-1,5,7-triazabicyclo[4.4.0] dec-5-enium [mTBDH]+ in [mTBDH][MeOCH2COO] compared to [mTBDH][OAc], as well as the strong cellulose dissolution capability of [mTBDH][MeOCH2COO] and excellent spinnability with a maximum draw ratio of 14. These findings demonstrate the high potential of using [mTBDH][MeOCH2COO] as the solvent to advance Ioncell fiber spinning technology by reducing the hydrolysis rate of [mTBDH]+, thereby minimizing loss during solvent recycling processes.

Molecular weight and spinnability of polyacrylonitrile: control with water and 1,8-diazabicyclo[5.4.0]undec-7-ene during anionic polymerization in dimethyl sulfoxide

A series of linear high molecular weight acrylonitrile homopolymers have been synthesized using controlled anionic polymerization. The possibility of producing polyacrylonitrile with a wide range of molecular weights by controlling the concentrations of metal-free initiator and water has been demonstrated. The resulting homopolymers exhibit excellent spinnability.

Upcycling of cellulosic textile waste with bacterial cellulose via Ioncell® technology

Currently the textile industry relies strongly on synthetic fibres and cotton, which contribute to many environmental problems. Man-made cellulosic fibres (MMCF) can offer sustainable alternatives. Herein, the development of Lyocell-type MMCF using bacterial cellulose (BC) as alternative raw material in the Ioncell® spinning process was investigated. BC, known for its high degree of polymerization (DP), crystallinity and strength was successfully dissolved in the ionic liquid (IL) 1,5-diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] to produce solutions with excellent spinnability. BC staple fibres displayed good mechanical properties and crystallinity (CI) and were spun into a yarn which was knitted into garments, demonstrating the potential of BC as suitable cellulose source for textile production. BC is also a valuable additive when recycling waste cellulose textiles (viscose fibres). The high DP and Cl of BC enhanced the spinnability in a viscose/BC blend, consequently improving the mechanical performance of the resulting fibres, as compared to neat viscose fibres.

Controllable synthesis of naphthalene-derived isotropic pitch with linear molecular structure via Blanc chloromethylation–dechlorination reaction

Isotropic pitches with high softening points were controllably synthesized using naphthalene (NAP) via Blanc chloromethylation–dechlorination. Under mild conditions, chloromethyl was introduced into the NAP ring in the presence of chloromethylation reagent. The chloromethylation products of NAP are mainly composed of 1-chloromethylnaphthalene (1-CMNP) and a small amount of 1,4-dichloromethylnaphthalene (1,4-DCMNP). The results of the thermodynamic and kinetic calculations confirmed that the alpha-hydrogen on the NAP ring was more susceptible to being substituted by chloromethyl during chloromethylation, resulting in the formation of 1-CMNP and 1,4-DCMNP. High-quality isotropic pitches with linear methylene-bridged NAP ring structures, characterized by high purity, a high H/C ratio, 100 % solubility in quinoline, and excellent spinnability, were obtained after thermal dechlorination polymerization. Due to their homogeneous isotropic phase, appropriate viscosity, and outstanding spinnability, the as-synthesized pitches were adopted as precursors to prepare isotropic pitch-based carbon fibers via melt spinning. Additionally, the investigation of the carbonization behavior of the as-synthesized pitches showed that the naphthalene-derived isotropic pitch obtained at a polymerization temperature of 380 °C had a 57 % carbon yield at 800 °C, and its derived semi-cokes displayed an isotropic texture, even when carbonized at 550 °C.

Preparation of spinnable mesophase pitch from pyrolyzed fuel oil by pressurized heat treatment and its application of carbon fiber

Petroleum residues are produced as by-products of petroleum refining. Recently, various effective non-fuel uses of petroleum residues have been considered toward a carbon-neutral society. Pyrolysis fuel oil (PFO) is one of the petroleum residues. Advanced utilization of PFO for future non-combustion applications is required. In this study, Mesophase pitch-based carbon fibers (MPCF) were successfully produced from PFO. Spinnable mesophase pitch (SMP), a precursor of MPCF, was prepared using PFO as a raw material through the pressurized heat treatment at 420°C-430 °C. PFO is from the naphtha catalytic cracking process for ethylene production and is mainly composed of 2–4 condensed polycyclic aromatic hydrocarbons (PAHs). The high temperature pressurized heat treatment could result in the PFO-derived SMPs with yield of 23.0 wt% and excellent spinnability. On the other hand, without pressurized heat treatment, the yield was 8.5 wt%. This indicates that pressurized heat treatment significantly contributed to the yield improvement. In addition, the preference for the conversion of PFO molecules into highly condensed PAHs via cata-condensation during pressurized heat treatment at 420°C-430 °C was observed, which may be the main reason for the high yield and excellent spinnability of the resulting SMPs. As a result, the obtained PFO-derived SMPs though the such high-temperature pressurized heat treatment provided the typical radial-random transversal textures and general mechanical performances of MPCF: The tensile strength and Young's modulus of the PFO-derived MPCF graphitized at 2400 °C showed high values of 1.9–2.7 GPa and 554–635 GPa, respectively.

Protective Topical Dual-Sided Nanofibrous Hemostatic Dressing Using Mussel and Silk Proteins with Multifunctionality of Hemostasis and Anti-Bacterial Infiltration.

Topical hemostatic agents are preferred for application to sensitive bleeding sites because of their immediate locoregional effects with less tissue damage. However, the majority of commercial hemostatic agents fail to provide stable tissue adhesion to bleeding wounds or act as physical barriers against contaminants. Hence, it has become necessary to investigate biologically favorable materials that can be applied and left within the body post-surgery. In this study, a dual-sided nanofibrous dressing for topical hemostasis is electrospun using a combination of two protein materials: bioengineered mussel adhesive protein (MAP) and silk fibroin (SF). The wound-adhesive inner layer is fabricated using dihydroxyphenylalanine (DOPA)-containing MAP, which promotes blood clotting by aggregation of hemocytes and activation of platelets. The anti-adhesive outer layer is composed of alcohol-treated hydrophobic SF, which has excellent spinnability and mechanical strength for fabrication. Because both proteins are fully biodegradable in vivo and biocompatible, the dressing would be suitable to be left in the body. Through in vivo evaluation using a rat liver damage model, significantly reduced clotting time and blood loss are confirmed, successfully demonstrating that the proposed dual-sided nanofibrous dressing has the right properties and characteristics as a topical hemostatic agent having dual functionality of hemostasis and physical protection.

Fabrication of cassava (Manihot esculenta Crantz) starch‐based ultrafine fibers: Investigation of fundamental and antimicrobial properties

AbstractMicro/nano‐based fibrous membranes loaded with antibacterial agents have been widely studied in the medical field. In this research, we describe the development of a new environmentally friendly medical dressing based on centrifugally spun cassava starch‐based ultrafine fibers loaded with nanosilver (Ag). For this purpose, the spinnability of amylopectin‐rich native cassava starch in a centrifugal spinning system was investigated. Polyvinyl alcohol (PVA) was applied to improve the water stability and mechanical properties of the starch‐based fibers, and the water stability of the fibers was further improved by posttreatment with formic acid. The morphology, structure, thermal, and tensile properties were studied. The results indicated that the native cassava starch showed excellent spinnability in the centrifugal spinning system. The tensile strength and water stability of the obtained fibrous membranes were improved by adding PVA and further improved after the posttreatment. The antibacterial properties of fibers loaded with Ag were evaluated through a bacteriostatic zone test, and the results showed that the fibers presented good antibacterial properties against Escherichia coli. Therefore, the obtained fibers have great potential for application in the medical dressing field.

Flame Retardancy and Mechanical Properties of Melt-Spun PA66 Fibers Prepared by End-Group Blocking Technology

Preparing flame-retardant polyamide 66 (PA66) fibers through melt spinning remains one of the biggest challenges nowadays. In this work, dipentaerythritol (Di-PE), an eco-friendly flame retardant, was blended into PA66 to prepare PA66/Di-PE composites and fibers. It was confirmed that Di-PE could significantly improve the flame-retardant properties of PA66 by blocking the terminal carboxyl groups, which was conducive to the formation of a continuous and compact char layer and the reduced production of combustible gas. The combustion results of the composites showed that the limiting oxygen index (LOI) increased from 23.5% to 29.4%, and underwriter laboratories 94 (UL-94) passed the V-0 grade. The peak of heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) decreased by 47.3%, 47.8%, and 44.8%, respectively, for the PA66/6 wt% Di-PE composite compared to those recorded for pure PA66. More importantly, the PA66/Di-PE composites possessed excellent spinnability. The prepared fibers still had good mechanical properties (tensile strength: 5.7 ± 0.2 cN/dtex), while maintaining good flame-retardant properties (LOI: 28.6%). This study provides an outstanding industrial production strategy for fabricating flame-retardant PA66 plastics and fibers.

Melt-blowing of silicane-modified phenolic fibrous mat for personal thermal protection

Thermal insulation fabric for personal thermal protection equipment subjected to harsh conditions is urgently needed but remains challenging. Here, a high-ortho-silicane-modified phenolic resin (SiPR) with linear molecular structure and excellent spinnability is synthesized and melt-blown as a fibrous nonwoven mat with small fiber diameter (less than 4 µm) and high porosity (88%). Benefitting from the synergistic effect, the cured SiPR nonwoven (SiPR-MBNM) demonstrates high heat resistance, flame retardance, and low heat conductivity, which endow it with excellent thermal insulation performance in high-temperature environments. Complemented with the high production capacity of melt-blowing technology, SiPR-MBNM offers promising prospect for personal thermal protection equipment subjected to harsh and high-temperature conditions.

Preparation of pitch precursor with excellent spinnability for general-purpose carbon fibre using coal tar pitch as raw material

Tetrahydrofuran (THF) extract of coal tar pitch (CTP) was used instead of blending CTP with pretreated pyrolysis fuel oil to prepare an isotropic pitch precursor with excellent spinnability for general-purpose carbon fibre through bromination–dehydrobromination. The feasibility and effectiveness of synthesising an isotropic pitch precursor derived from THF-soluble (CTP-THFs) is demonstrated in this study. The results show that CTP-THFs contains more light components than CTP; CTP-THFs and CTP monomer proportions were 62.52% and 45.32%, respectively. However, based on comparisons of CTP-THFsBr0 and CTPBr0 characterisations, CTP-THFs exhibits better polycondensation than CTP. Bromination–dehydrobromination promotes polycondensation of pitch precursors, leading to greater carbon aromaticity in CTP-THFsBr5, CTP-THFsBr10, and CTP-THFsBr15 than that in CTP-THFsBr0 and CTPBr0. CTP-THFsBr5 and CTP-THFsBr10 have excellent spinnability even with softening points as high as 230 °C. The peri-condensed carbon and carbon aromaticity of CTP-THFsBr5 and CTP-THFsBr10 are high owing to the higher degree of polycondensation; however, they still possess a more linear molecular structure. The as-prepared carbon fibre exhibits homogeneity and uniformity, and the mechanical performance is comparable with that of commercial general-purpose carbon fibre products.

Highly efficient, low-resistant, well-ordered PAN nanofiber membranes for air filtration

Disordered pore structures present in traditional fiber filtration materials often mean they are incapable of simultaneously achieving high filtration efficiencies and low air resistance. In this study, the excellent spinnability, hydrophobicity, and stability properties of polyacrylonitrile (PAN) have been exploited to prepare electrospun nanofiber membranes containing well-ordered fibers with diameters ranging from 240 to 404 nm and pore sizes ranging from 1.91 to 6.45 µm. These nanofiber membranes exhibit excellent air filtration efficiencies ranging from 94.83 % to 99.60 % for aerosol particles with diameters of around 300 nm, which occurs with a corresponding pressure drop from 33 to 98 Pa. Three-dimensional (3D) models of disordered nanofiber membranes, standard-ordered nanofiber membranes, and cross-ordered nanofiber membranes were constructed, which confirm that the ordered structure can greatly reduce the pressure drop of the fiber membranes whilst maintaining filtration efficiency. The new well-ordered membranes exhibit significantly higher filtration efficiencies and lower air resistance than traditional fiber air membranes that contain a more disordered structure, meaning they should be well-suited for air-filtration applications.

Controllable synthesis of a carbonaceous pitch from molecular dimension by a novel method of chlorination-dechlorination

The carbonaceous pitch derived from coal liquefaction residue was controllably synthesized from the molecular dimension with a novel method, chlorination–dechlorination. The factors affecting the qualities of chlorination–dechlorination derived pitch, including chlorine ratios, were studied. The qualities of the pitches prepared with chlorination–dechlorination and the conventional thermal condensation method are compared. The carbons in the prepared carbonaceous pitch mainly exist in aromatic structures, which are oligomerized to transform dimers and trimers by chlorination–dechlorination. The C/H ratio, average molecular weight, and carbon aromaticity are increased by chlorination–dechlorination. According to the result of the simulation, the hydrogen atoms on the side chain of aromatic compounds are easier to be mono-substituted by chlorine atoms during chlorination, and then the substituting chlorine atoms connect with other hydrogen atoms to form to escape out of the reactor in the formation of hydrogen chloride during dechlorination, making the aromatic compounds oligomerize with each other. Thus, the conclusion that the chlorinated pitch has a more linear and cross-linking molecular structure is demonstrated, which is also confirmed by the results of 13C NMR. The pitch precursors exhibit better thermal stability and thermochemical property even when the softening point has been raised to around 230 ℃ owing to the linear and cross-linking molecular structure. In addition, the pitches synthesized by the method of chlorination–dechlorination shows a more homogeneous state, while the pitch produced by thermal condensation contains a small number of powdery coke particles, and they also possess more excellent spinnability and appropriate viscosity for the process of melt-spinning. Chlorination–dechlorination can be used to achieve the controllable synthesis of the carbonaceous pitch from the molecular dimension. The properties of derived pitches are better as the addition of chlorine increases.

Toward heat resistant polylactide blend fibers via incorporation of low poly[(R)‐3‐hydroxybutyrate‐co‐4‐hydroxybutyrate] content

AbstractBlending high content of polyhydroxyalkanoates (PHAs ≥ 30 wt.%) with polylactide (PLA) provides an effective strategy to significantly improve heat resistance of PLA fibers. However, it has proven challenging to maintain good spinnability of the PLA/PHAs blends with the high content of PHAs. In this study, a series of poly(L‐lactide) (PLLA)/poly[(R)‐3‐hydroxybutyrate‐co‐4‐hydroxybutyrate] (P34HB) blend fibers with low P34HB content (≤ 8 wt.%) is successfully fabricated with excellent spinnability. The incorporation of P34HB contributes to a substantially improved heat resistance of the PLLA/P34HB blend fibers, as evidenced by a notable reduction in boiling water shrinkage from ca. 80% to 9%. This exceptionally improved heat resistance is closely related to substantial increase in crystallinity of PLLA in the blend fibers. Specifically, the addition of low P34HB content remarkably enhances chain mobility of PLLA chains, as such reduces crystallization half‐times (t1/2) and accelerates crystallization of PLLA. In fact, the amorphous P34HB phase favors crystal growth of PLLA phase rather than heterogeneous nucleation inferred previously. These results provide a facile and effective method to produce PLLA/P34HB blend fibers with enhanced heat resistance and sound spinnability.

Functionalization of PET with carbon dots as copolymerizable flame retardants for the excellent smoke suppressants and mechanical properties

Based on the excellent flame retardant performance, environment-friendly and abundant surface functional groups, Carbon Dots (CDs) were adopted as copolymerizable flame retardants for Poly(ethylene terephthalate)(PET) for the first time. The CDs with gelatin as precursor (gCDs) were synthesized by one-step hydrothermal method and copolymerized with pure terephthalic acid (PTA) and ethylene glycol(EG) to prepare flame retardant copolyester (gCDs-PET) based on the hydroxyl and amine groups on the surface of gCDs by in situ polymerization. It is demonstrated that gCDs-PET had showed better smoke suppressant and higher flame retardancy than pristine PET. The limiting oxygen index (LOI) of gCDs-PET composites achieved to 29% with the addition of 2.0 wt% gCDs. What is more, cone calorimeter tests showed that the peak value of heat release rate(pk-HRR) greatly decreased 42.66% and the total smoke production (TSP) reduced 62.64%. Besides, the flame-retardant mechanism disclosed that gCDs catalyzes the thermal decomposition of PET to form a shielding carbon layer, which handicap the release of combustible materials to the outside and expand the as-formed char, so that interrupt the combustion reaction. Furthermore, mechanical properties and spinnability of gCDs-PET was evaluated. It was demonstrated that the addition of gCDs into PET could enhance the mechanical strength and gCDs-PET could be made to fibers with excellent spinnability.

Facile synthesis of a novel transparent melt‐spinnable polysilazane

AbstractIn this study, a novel colorless and transparent polysilazane (PSZ) with excellent spinnability was facilely synthesized via the thermal polymerization of silazane oligomer at 330℃. The silazane precursor was fabricated by one‐step copolycondensation of methyldichlorosilane (CH3SiHCl2) and dimethyldichlorosilane ((CH3)2SiCl2) in various ratios at 0℃ without catalyst during the reaction. The chemical composition, molecule structure, molecular weight and ceramic yield of PSZ were investigated by gel permeation chromatography (GPC), Fourier transform infrared (FT‐IR), thermogravimetric analysis (TGA) and pyrolysis chromatography‐mass spectrometry (PY‐GC/MS). The optimized novel transparent melt‐spinnable PSZ was a colorless and transparent brittle solid with a Mw = 14,231 and a melting point of 100℃, which was prepared with an optimal molar ratio of raw materials at 1.9:1 (CH3SiHCl2: (CH3)2SiCl2). Fibers with various diameters were spun using a homemade melt spinning setup at 90–120°C. The obtained PSZ showed outstanding spinnability, and the prepared continuous fibers exhibited a uniform diameter (10–80 microns) and a smooth surface up to 1000 meters long. In addition, possible polymerization mechanisms of PSZ were also discussed. The PSZ showed the excellent rheological properties in melt‐spinning as a potential precursor for Si3N4 fibers. The novel optically transparent polysilazane material also have great potential applications in optical technology and engineering.

Preparation of isotropic spinnable pitch with high-spinnability by co-carbonization of coal tar pitch and bio-asphalt

Co-carbonization of coal tar pitch (CTP) with bio-asphalt (BA) was performed to prepare spinnable pitch with suitable softening point and excellent spinnability for general purpose carbon fiber. The co-carbonization mechanism and the correlation between spinnability and molecular structure of prepared pitch were clarified. BA produced from the pyrolysis of biomass is abundant of aliphatic units and oxygen-containing groups, leading to high reactivity during carbonization. The co-carbonization reactions mainly depend on the mutual cross-linking among CTP and BA molecules, which are principally triggered by active oxygen-containing groups of BA. The formed cross-linked macromolecules could further promote the polymerization degree of pitch molecules; thus, the spinnable pitch with suitable softening point could be obtained by simply thermal treatment of blended pitches at a relatively moderate condition (<350 °C). The properties of the pitch could be optimized by changing the blending ratio of CTP to BA. Moreover, the prepared carbon fibers demonstrated distinct features, especially surface profiles. It is expected to provide a new strategy for the preparation of isotropic spinnable pitch in a relatively simple approach.

The preparation and characterization of a heterocyclic meta-aramid fiber with outstanding thermal stability

A heterocyclic meta-aramid fiber containing benzimidazole structure was prepared by the low-temperature polycondensation of m-phenylenediamine, 2-(4-aminophenyl)-5-benzimidazole, and isophthaloyl dichloride, followed by dry-jet wet spinning. The structure and properties of the heterocyclic modified meta-aramid (h-aramid for short) were explored and compared with poly(isophthaloylmetaphenylene diamine) (m-aramid for short). H-aramid exhibits excellent spinnability. The surface of the fiber is smooth and even, with a partially ordered structure. Mechanical properties, thermal resistance, and flame retardant of h-aramid are significantly enhanced as the introduction of benzimidazole can not only increase the rigidity of molecular chains but also strengthen hydrogen bonds and act as physical crosslinking points. The strength and modulus of h-aramid are up to 0.84 GPa and 16.66 GPa, respectively, with an elongation at break of 20%. The glass transition temperature and melting temperature of h-aramid reach 302°C and 356°C, respectively, about 30°C and 40°C higher than that of m-aramid. Temperature of 10 wt% weight loss under nitrogen and air atmosphere is 17°C and 39°C higher than those of m-aramid. Besides, the thermal degradation behavior of h-aramid was studied, and its degradation process and mechanism was proposed.

Preparation of PVA Fluorescent Gel and Luminescence of Europium Sensitized by Terbium (III).

Polyvinyl alcohol (PVA) gel has a very wide range of applications in agriculture, military, industry, and other fields. As a widely used water-soluble polymer, PVA has good mechanical properties, excellent spinnability, good hydrophilicity, remarkable physical and chemical stability, good film formation, is non-polluting, and exhibits good natural degradation and biocompatibility. It is an ideal gel preparation material. Incorporation of rare-earth elements into PVA polymers can be used to prepare rare-earth luminescent gel materials. Results show that the luminescent efficiency of complexes is mainly related to their structure, ligand substituents, synergists, and the electronic configuration of doped rare-earth ions. Fluorescent gel films were prepared by adding europium, terbium, and europium/terbium co-doped into PVA, and their fluorescence properties were compared and analyzed. It was found that, in addition to the above factors, the sensitization of terbium to europium, and the fluorescence-quenching effect of hydroxyl groups, will influence the fluorescence properties. This has opened a new route for the application of rare-earth materials and may have value in the field of new materials.

Preparation and characterization of high-spinnability isotropic pitch from 1-methylnaphthalene-extracted low-rank coal by co-carbonization with petroleum residue

Coal extract produced by solvent extraction of low-rank coal is not suitable for spinning due to its high oxygen content. In order to effectively overcome this limitation, soft pitch was produced by co-carbonization of coal extract and petroleum residues. The decrease in oxygen content was confirmed by physical property analyses of the soft pitches blended at different mixing ratios. A bridge/hydroaromatic structure of the soft pitch was observed during the co-carbonization. The produced spinnable pitch had a high spinnability and a softening point of 230 °C. This spinnable pitch, prepared by solvent extraction of low-rank coal, showed excellent spinnability and was heat-treated at 800 °C for 5 min to produce isotropic carbon fibers having diameters of 7 μm and a tensile strength of 1189 MPa. Thus, the co-carbonization of coal extract and petroleum residue is an effective method for the production of inexpensive spinnable pitch for isotropic carbon-fiber manufacture.

Direct and complete utilization of agricultural straw to fabricate all-biomass films with high-strength, high-haze and UV-shielding properties

It is of vital significance to fabricate high-value-added materials from agricultural wastes by environmentally friendly and cost-effective processes. In this work, we propose an approach to directly and completely convert agricultural straw into multifunctional all-biomass films by introducing an entanglement network of additional cellulose to enhance the strength of the regenerated straw. First, natural wheat straw is dissolved in the ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). Then, a small amount of cellulose with a high degree of polymerization (DP) is introduced to obtain straw/cellulose/AmimCl solutions, which are subsequently soaked in water for biomass regeneration, washed and dried to obtain straw/cellulose films. Dynamic shear rheological test confirms that after adding high-DP cellulose, an enhanced entanglement network forms in the solutions, which is essential to the processing and mechanical properties of materials. Extensional rheological test indicates that straw/cellulose/AmimCl solutions exhibit excellent spinnability and film-forming properties based on a significant increase in the capillary break-up time. Therefore, after regeneration in water, straw-based all-biomass films with high mechanical strength are obtained. When the content of additional wood pulp (WP, DP = 1300) with respect to total solids is 25 wt%, the obtained straw/WP all-biomass film reaches a tensile strength of 62 MPa. More interestingly, because there is no intentional chemical pretreatment and compositional isolation involved in this process, almost all of the components in straw, such as cellulose, lignin, hemicellulose and inorganic compounds, are retained in the final films. Thus, the resultant films have a superhigh haze of 97% while preventing 97% UVA (320–400 nm) and almost 100% UVB (280–320 nm). In sum, we demonstrate the complete and value-added utilization of low-grade bioresources by a facile, green and economical process to fabricate high-strength, high-haze and UV-shielding all-biomass films, which have great potential in low-cost, biodegradable and environmentally friendly packaging.