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Abstract 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 [...]

Improving the flame retardant performance of polycaprolactam (PA6) will greatly expand its applications. At present, the commonly used reactive flame retardants of PA6 mainly come from the petrochemical industry. Therefore, D-glucopyranose, a green renewable biomass, is selected and bonded to the PA6 molecular chain through in situ polymerization to obtain a series of flame retardant polyamides (PA6/G1) and their high-speed melt-spun fibers. When its added amount was 2 wt%, the LOI and UL-94 of PA6/G1 reached 29.4 Vol% and V-0 level, and the char residue was 529.4% higher than that of neat PA6 after thermogravimetric test. D-glucopyranose contains a polyhydroxy structure that can capture the hydrogen radicals generated by homogeneous cracking during combustion, increasing the content of C[O.sub.2] and [H.sub.2]O and forming a smooth and dense carbon isolation layer. Thus, the synergistic flame retardant effect of green D-glucopyranose on the gas and condensed phases of PA6 is achieved. KEYWORDS D-glucopyranose, fiber, flame retardant, polyamide 6, 1 | INTRODUCTION Polycaprolactam (PA6) fiber refers to a type of synthetic fiber whose molecular chain is connected by amide bonds (--CO--NH--), and is the second synthetic fiber to realize [...]

In response to an investigation on the paths of changes in the crystallization and radial differences during the forming process of nascent fibers, in this study, we conducted numerical simulation and analyzed the changes in crystallization mechanical parameters and tensile properties through a fluid dynamics two-phase model. The model was based on the melt-spinning method focusing on melt spinning, the environment of POLYFLOW, and the method of joint simulation, coupled with Nakamura crystallization kinetics, including the development of process collaborative parameters, stretch-induced crystallization, viscoelasticity, filament cooling, gravity term, inertia, and air resistance. Finally, for nylon 6 BHS and CN9987 resin spinning, the model successfully predicted the distribution changes in temperature, velocity, strain rate tensor, birefringence, and stress tensor along the axial and radial fibers and obtained the variation pattern of fibers' crystallinity along the entire spinning process under different stretching rates. Furthermore, we also explored the effects of spinning conditions, including inlet flow rate, winding speeds, and the extrusion temperature, on the fibers' crystallization process and obtained the influence rules of different spinning conditions on fiber crystallization. Knowing the paths of changes in mechanical performance can provide important guidance and optimization strategies for the future industrial preparation of high-performance fibers. [ABSTRACT FROM AUTHOR]

Hydrogen bonding is the prerequisite for polyamide fibers to have better stress–strain behavior. It affects the crystal structure of polyamide fibers, such as orientation and periodic arrangement. To illustrate the effect of intermolecular hydrogen bonding on fiber orientation structure and macroscopic mechanical properties, this work uses conventional polyamide resin doped with high molecular weight components to construct polymer compounds with discrete distribution characteristics. By analyzing the changes in intermolecular hydrogen bonds, melt rheological properties, non‐isothermal crystallization behaviors, the impact of hydrogen bonds on the crystal structure and orientation structure and thus on the fiber strength was clarified. The doping of high molecular weight components can make the compound form more hydrogen bonds and inhibit the relaxation of molecular chains through entanglement, thereby promoting melt non‐isothermal crystallization process and increasing complex viscosity η* and storage mode G'. 1D and 2D wide‐angle and small‐angle X‐ray scattering show that doping components reduce crystal size of α1(200) and α2(002, 202) planes from 4.19 to 3.47 nm and 5.88 to 4.96 nm, resulting in a denser long‐period structure. Through the strategy of this work, polyamide 6 fibers' tensile strength is effectively improved by18%, and the mechanical properties are significantly improved. Highlights: High‐strength polyamide compound fibers were prepared.Discretely distributed compounds are achieved.Discretely distributed molecular weight enabled hydrogen bonding regulation.Hydrogen bonding‐induced compound fiber crystal structure.Multiple external fields induced crystallization and orientation structures. [ABSTRACT FROM AUTHOR]

The influence of axial steric hindrance in α-diimine nickel catalysts on ethylene polymerization is paramount for enhancing the catalytic performance especially in terms of thermal stability and polymer molecular weights. In this study, a set of five nonsymmetrical 1,2-bis(arylimino)acenaphthene–nickel complexes, incorporating 2,6-bis(bis(4-fluorophenyl)methyl)-3,4,5-trimethoxyaniline and 2,4,6-trialkylaniline moieties, was prepared to tailor the catalytic attributes for ethylene polymerization. In-depth studies on the polymerization of ethylene, using two different cocatalysts and different reaction conditions, revealed exceptional catalytic activities for these precatalysts with activity levels as high as 20.3 × 106 g mol−1 h−1 at 30 °C and high molecular weights of the obtained polyethylene with adjustable branching degrees and distributions. Reactions at elevated temperatures validated the enhanced thermal stability of Ni-Me2 precatalysts, displaying a noteworthy activity of 1.4 × 106 g mol−1 h−1 at 100 °C. Polyethylene derived from more sterically hindered nickel complexes exhibited relatively higher molecular weights and branching degrees compared to less hindered analogues. This trend was consistent across mechanical and elastic properties, which ranged from 6.1 MPa to 10.6 MPa and 26% to 49%, respectively. Moreover, the manipulation of branching degree by increasing the reaction temperature led to an elastic recovery of up to 63%, indicating potential formation of thermoplastic polyethylene elastomers. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate) (PET), extensively employed in bottles, film, and fiber manufacture, has generated persistent environmental contamination due to its non‐degradable nature. The resolution of this issue requires the conversion of waste PET into valuable products, often achieved through depolymerization into monomers. However, the laborious purification procedures involved in the extraction of monomers pose challenges and constraints on the complete utilization of PET. Herein, a strategy is demonstrated for the polymer‐to‐polymer upcycling of waste PET into high‐value biodegradable and programmable materials named PEXT. This process involves reversible transesterifications dependent on ester bonds, wherein commercially available X‐monomers from aliphatic diacids and diols are introduced, utilizing existing industrial equipment for complete PET utilization. PEXT features a programmable molecular structure, delivering tailored mechanical, thermal, and biodegradation performance. Notably, PEXT exhibits superior mechanical performance, with a maximal elongation at break of 3419.2 % and a toughness of 270.79 MJ m−3. These characteristics make PEXT suitable for numerous applications, including shape‐memory materials, transparent films, and fracture‐resistant stretchable components. Significantly, PEXT allows closed‐loop recycling within specific biodegradable analogs by reprograming PET or X‐monomers. This strategy not only offers cost‐effective advantages in large‐scale upcycling of waste PET into advanced materials but also demonstrates its enormous prospect in environmental conservation. [ABSTRACT FROM AUTHOR]

Printing and dyeing wastewater, that is discharged after textile printing and dyeing processing, can cause irreversible damage to the aquatic ecosystem and harm the health of human beings. Till now, completely and readily removing dye molecules from industrial wastewater using a single catalyst rather than the combination of several materials remains a significant challenge. Herein, in situ preparation of carbon nanotube membranes (N‐CNTM and N‐TiO2‐CNTM) are reported that are doped using N with/without TiO2, respectively. These membranes can simultaneously function as an adsorber, a photo‐catalyst, and an electrocatalyst to efficiently remove dye pollutes from industrial waste water. Further researches reveal that the formation of p‐n type heterojunction inside of the N‐CNTM and N‐TiO2‐CNTM, can improve the hole separation and charge storage abilities, resulting in the efficient removal of dyes in the industrial waste water. This work provides a promising approach for the preparation of functionalized carbon nanotubes derived from waste biomass for the treatment of industrial water, reflecting the concept of treating waste with waste. [ABSTRACT FROM AUTHOR]

The high value‐added application of lignin is of great significance for the effective utilization of biomass and environmental protection. In this work, TiO2‐loaded lignin‐derived carbon nanofibers (TiO2@LCNFs) are developed by the process of electrospinning, per‐oxidation, and carbonization. The effects of TiO2 content, carbonization temperature, initial RhB concentration, and solution pH value on the photocatalytic efficiency are systematically studied. Up to 86% photocatalytic efficiency and excellent cycling stability of the TiO2@LCNFs to rhodamine B under optimized conditions are achieved. The superior catalytic property of the TiO2@LCNFs can be attributed to the synergistic effect of the uniform distribution of TiO2 on the fiber surface and the good electrical conductivity of LCNFs. It is expected that this work will provide some guidance for the preparation of efficient photocatalytic materials, especially those based on biomass‐derived fiber materials. [ABSTRACT FROM AUTHOR]