Stereocomplex polylactide (SC-PLA) provides an effective route to improve heat-resistance through the formation of SC-PLA crystallites driven by hydrogen bonding interactions between poly(l-lactide) ...(PLLA) and poly(d-lactide) (PDLA). Great progress has been made in low molecular-weight SC-PLA compounds. However, the development of strategies for exclusive stereocomplexation in high molecular-weight (high-MW) PLLA/PDLA racemic blends quenched from isotropic melt remains challenging. In this study, in-situ reactive melt-spinning of commercially available high-MW PLLA/PDLA blend with a new transesterification catalyst (i.e., sodium octanoate in MB) was devised as an effective strategy to prepare blends containing stereo-block PLA (sb-PLA) copolymers. As a result, the sb-PLA copolymers restricted phase separation and further promoted relatively weak CH3⋯ OC hydrogen bonding interactions, along with the development of the exclusive SC-PLA crystallites with low crystalline thickness (Lc) in PLLA/PDLA/MB blend fibers drawn at low temperatures (≤102 °C). In contrast, extremely limited transesterification reaction in PLLA/PDLA melt led to the phase separation and the resultant separate domains of PLLA or PDLA restricted the occurrence of the CH3⋯ OC hydrogen bonding interactions in the PLLA/PDLA blend fibers drawn at low temperatures (≤120 °C). Only when the PLLA/PDLA blend fibers were drawn at a high temperature (198 °C), the strong CH3⋯ OC hydrogen bonding interactions could be formed, along with the formation of the exclusive SC-PLA crystallites with high Lc. These findings provide a facile and effective strategy to develop industrial-scale PLA fibers containing the exclusive SC-PLA crystallites with improved heat-resistance.
All SC-PLA fibers with improved heat-resistance were prepared via in-situ reactive melt-spinning and hot-drawing (≤102 °C) of linear high-MW PLLA/PDLA blend with a transesterification catalyst. Display omitted
•All SC-PLA fibers with improved heat-resistance were prepared by in-situ reactive melt-spinning process.•Sb-PLA copolymers were in-situ generated in PLLA/PDLA/MB melt through transesterification reaction.•The sb-PLA copolymers restricted phase separation, promoting CH3⋯ OC interactions in drawn fibers (≤102 °C).•The CH3⋯ OC interactions facilitated the formation of exclusive SC-PLA crystallites in drawn fibers (≤102 °C).
A novel flame retardant polyamide 6 (PA6)/bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-derivative (PHED) nanocomposite textile filament yarns were developed. The scalable ...production approach includes in situ water-catalyzed ring-opening polymerization of ε-caprolactam in the presence of the flame retardant PHED followed by melt-spinning of nanocomposite filament yarns and production of knitted fabrics. The specific chemical structure of the PHED additive enabled its excellent miscibility with molten ε-caprolactam and the uninterrupted polymerization of ε-caprolactam. The produced PA6/PHED nanocomposite was characterized by the preserved molecular structure of the polyamide 6 and uniformly distributed nano-dispersed FR at concentrations of 10 and 15 wt %. The PA6/PHED nanocomposite structure was successfully preserved after the melt-spinning processing. The PA6 nanocomposite filament yarns at the applied 15 wt %. loading of PHED showed (a) increased thermo-oxidative stability compared to neat PA6 up to 500 °C, with a 43% higher residue at 500 °C and (b) self-extinguishment of fiber strand and knitted samples within 1 s in standard vertical flame spread tests (ASTM D6413), followed by the significant reduction of the melt-dripping and the melt-drop flammability. Additionally, 1.2 mm-tick PA6/PHED bar samples achieved a V0 rating in UL94 vertical burning test at the applied 10 wt % concentration of PHED. This innovative and scalable approach could pave the way for the production of new-generation nanocomposite PA6 filament yarns with self-extinguishing properties at the macro-scale, which would be highly beneficial for increasing fire safety, whilst maintaining the use of a DOPO derivative at the minimum level.
A new scalable approach is established to produce the first-ever polyamide 6/DOPO-derivative nanocomposite filament yarns and knitted fabrics with superior flame retardancy and self-extinguishing properties. The in situ approach for the incorporation of the organophosphorus additive of specific chemical structure in the PA6 matrix guarantees its uniform distribution and nanodispersion as well as the successful melt-spinning of textile filaments with highly effective flame retardancy, whilst maintaining the use of a DOPO-derivative at the minimum level. Display omitted
•Flame retardant PA6/PHED nanocomposite was produced by in situ polymerization approach.•Textile filament yarns were successfully melt-spun from produced nanocomposites.•PHED increased thermo-oxidative stability of PA6 up to 500 °C, with 43% higher residue at 500 °C.•Self-extinction within 1 s for PA6/PHED fiber strand and knitted fabric was achieved in vertical flame spread tests (ASTM D6413).•UL94 V-0 rating was achieved for 1.2 mm-tick PA6/PHED bar samples with 10 wt % of PHED.
•ZrC precursor fibers were prepared from zirconium-containing polymer.•The centrifugal melt spinning process is conducted in air atmosphere.•Spinning auxiliaries are not needed in this process.•This ...process can produce qualified fibers at low spinning temperatures (60 °C).
ZrC precursor fibers were prepared from a paste of 75% zirconium-containing polymer and 25% toluene by centrifugal melt-spinning. This process can rapidly and conveniently produce fibers at a low spinning temperature (60 °C) without requirement of inert atmosphere or spinning auxiliaries. Interestingly, when the content of the zirconium-containing polymer was 100% or 50%, no precursor fiber was obtained. After pyrolysis at 1500 °C, the precursor fibers were converted into ZrC ceramic fibers with a diameter of 15.5 μm. Finally, the relationship between the pyrolysis temperature and phase composition was studied, and a pyrolysis mechanism was proposed.
For the improvement of the processing of melt‐spun lignin‐based fibers, the use of a spinning oil is necessary. The use of spinning oils is standard for the processing of PAN based carbon fiber ...precursors. Since no commercial spinning preparations for lignin fibers are available on the market, a study on different oils, such as technical oils, food‐grade oils or spinning avivages, is performed. A stepwise approach with applied tests (viscosity measurement, fiber etching, melt‐spinning, stabilization, carbonization) was developed to eliminate oils which are not suitable. The physical properties of the tested oils are determined and spectroscopic studies of these avivages are performed. Mechanical properties are characterized for as‐spun lignin fibers, stabilized lignin‐based fibers and lignin‐based carbon fibers with and without a spinning preparation. Four of seven tested spinning oils improve the handling during the processing of lignin‐based fibers but only two spinning oils lead to good quality carbon fibers and improve even the tensile strength of the resulting carbon fibers.
The use of a spinning oil enhances the lignin‐based fiber processing on a melt‐spinning line. Different technical oils, food‐grade oils as well as commercial spinning preparations for polymer and viscose fibers are characterized and analyzed. Only two tested oils are suitable for the processing of lignin‐based carbon fiber precursors.
Fine poly(ϵ-caprolactone) (PCL) filaments (diameter: 59–92 μm) were successfully melt-spun with modified drawing setups to prevent draw instabilities. Depending on the production parameters, ...different mechanical properties were obtained (tensile strength: 302–456 MPa, elongation at break: 69–88%). These variations are related to subtle structural differences, which we have analyzed with wide-angle x-ray diffraction (WAXD) and small-angle x-ray scattering (SAXS). SAXS was used to determine crystal widths and the spacing between crystals along the filament axis. Additionally, 2D WAXD patterns were simulated and WAXD profiles were fitted. The detailed 2D WAXD analysis revealed that a highly-oriented non-crystalline mesophase is present in drawn PCL filaments, which is most-likely situated in-between PCL crystals. A large amount of this mesophase (>16%), combined with high crystalline orientation and perfect crystals, led to higher tensile strength values. We also confirmed that PCL chains pack with non-planar chain conformations in the unit cell.
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•Upscalable melt-spinning procedure for fine poly(ϵ-caprolactone) filaments.•Structure-mechanical property relationship in PCL filaments.•2D WAXD simulations and fits reveal the existence of a mesophase.•Structural analysis with SAXS: crystal sizes and long spacing.
As-spun Ti-rich Ti50.9Ni48.9Si0.2 ribbon showed recoverable superelastic strain of 4.5%, which was associated with elastocaloric cooling of 11.3 K. Cyclic superelastic tests showed that the ribbon ...exhibited great functional stability. The experimental results demonstrated that the melt-spinning process could improve the functionality of TiNi shape memory alloy.
•A magnetic field assisted melt-spinning process is used to inhibit the surface crystallization.•Applied magnetic field can suppress the formation of compounds and enhance the ...AFA.•Fe84.75Si2B9P3C0.5Cu0.75 alloy ribbon prepared with IRMs exhibit superb magnetic properties.•The Lorentz force, magnetic force and the vibration during solidification are the reasons.
Fe-based soft-magnetic amorphous and nanocrystalline ribbons made with a single-side fast-cooling process always suffer from the surface crystallization which deteriorates the magnetic properties and inhibits the wide applications. In this study, a static magnetic field assisted melt-spinning process was employed to prepare the typical Fe84.75Si2B9P3C0.5Cu0.75 alloy ribbon with an attractive application prospect. According to the comparative investigations of the crystallization behavior, structural evolution process and magnetic properties, it is found that the applied magnetic field can effectively inhibit the formation of compound phases and decrease the size of textured α-Fe grains in the surface layer of the as-spun ribbon. The Fe84.75Si2B9P3C0.5Cu0.75 samples made with low purity raw materials and under an optimal field exhibit superior magnetic properties, including a high saturation magnetization (Bs) over 1.82 T, low coercivity (Hc) of 8.5 A/m, high permeability (μ) of 2.76 × 104 at 1 kHz and much lower losses, after nanocrystallization by annealing. The apparent effect of the applied magnetic field was discussed from the disturbance of a Lorentz force of the fast-moving molten alloy and a magnetic force of preformed grains in a magnetic field during the melt-spinning process. These results provide a novel solution of surface crystallization and an effective route for improving magnetic properties of Fe-based amorphous and nanocrystalline alloy ribbons.
•The (Sm,Zr)Fe10 alloys consisted of the TbCu7-type and α-Fe phases.•The (Sm,Zr)Fe9.5Ti0.5 alloys consisted of the Th2Zn17-type and α-Fe phases.•The substitution of Ti for Fe in the (Sm,Zr)Fe10 ...alloys increased the coercivity.
(Sm,Zr)Fe10 and (Sm,Zr)Fe9.5Ti0.5 alloys were obtained by the melt-spinning technique in order to investigate the possibility of producing high-coercivity Sm-Fe alloys without nitrogenation. The (Sm,Zr)Fe10 alloys contained the TbCu7-type and α-Fe phases and exhibited a maximum coercivity of 1.88 kOe in the case of the (Sm0.9Zr0.1)Fe10 ribbon annealed at 1073 K. On the other hand, the (Sm,Zr)Fe9.5Ti0.5 alloys contained the Th2Zn17-type and α-Fe phases and showed a maximum coercivity of 4.5 kOe when the (Sm0.7Zr0.3)Fe9.5Ti0.5 ribbon was annealed at 1173 K.
Conventional local drug delivery systems often encounter issues such as burst-release, limited drug reservoirs, rigidity, and low mechanical performance. We present an innovative approach to local ...drug delivery utilizing melt-spun drug-loaded liquid-core filaments (LiCoFs). LiCoFs were produced, incorporating fluorescein sodium salt as the model drug, dissolved in various liquid core materials, and enveloped by poly(ε-caprolactone) as the sheath material. We assessed thermal, mechanical, and structural properties of LiCoFs and have conducted extensive drug diffusion trials. Some trials involved pre-exchange of the liquid core with ibuprofen, bovine serum albumin–fluorescein isothiocyanate and methylene blue solutions using a pumping device. It was observed that diffusion mechanisms and diffusion rates depend on temperature, core size/sheath thickness, sheath permeability, carrier liquid type, drug molecule properties, and the drug's affinity to the sheath polymer. These drug-loaded LiCoFs pave the way towards a new generation of medical textiles facilitating controlled, local drug delivery.
(Image sources: Adobe Stock. Liquid-filled fiber: Adapted image from "sveta – stock.adobe.com", Other images:"Todor Rusinov – stock.adobe.com", "Casanayafana/Shutterstock.com"). Display omitted
•Novel drug delivery method: melt-spun liquid-core fibers (LiCoFs).•Continuous meltspinning process to make drug-loaded LiCoFs.•Diffusion or pressure controlled local drug-delivery.•Large drug reservoir, high durability and mechanical performance of LiCoFs.
•A general, scalable, and green physical approach for synthesizing Pt-RE alloys.•The Pt3Y alloy offers a greatly improved activity and robust stability.•The optimal charge transfer by incorporating ...RE accelerates the ORR kinetics.•The Pt3Y delivered more robust durability by hindering the surface Pt escape.
Platinum-rare earth (Pt-RE) alloys are effective oxygen reduction reaction (ORR) catalysts, which are promising to show robust durability in proton-exchange membrane fuel cells (PEMFCs). Whereas, the large difference in reduction potentials between the two kinds of metals and the very oxophilicity of RE elements bring big challenges in the controllable synthesis of Pt-RE alloys. Herein we propose a general and scalable strategy to synthesize Pt-RE catalysts with tunable compositions and microstructures. The as-obtained catalysts possess a lamellar structure with hierarchical pore sizes ranging from 4 to 8 nm and a typical face-centered cubic (FCC) crystalline structure, and the Pt and RE are homogeneously distributed in the alloys. The electronic structures of Pt are well modulated by incorporating RE atoms, resulting in the adjusted d band center for these Pt-RE alloys compare with Pt, which facilitates OH* adsorption behavior and accelerate the ORR kinetics. Furthermore, the energy barrier for Pt demetallation is enhanced by incorporating of RE into the Pt lattice, which significantly enhances ORR durability. Notably, the optimal Pt3Y catalyst exhibits a greatly improved catalytic activity, including a large half-wave potential (0.89 V, at an ultralow Pt loading of 7.8 μg cm−2), high mass activity (0.53 A mg−1 at 0.9 ViR-free) and robust stability (0.01 V decay after 60,000 cycles) exceeding the commercial Pt/C (0.06 V decay after 30,000 cycles). This study provides a new facile strategy for the controllable preparation of Pt-RE alloys, which might pave the way for the large-scale applications of PEMFCs.
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