Fibers and Polymers最新文献

The functional group distribution and skin–core structure of polyacrylonitrile (PAN) pre-oxidized fibers have been evaluated by solid-state ¹³C-NMR, electron probe micro-analysis, element analysis, nano-infrared spectroscopy atomic force microscopy, and optical microscopy. The pre-oxidized fibers exhibited a skin–core structure with high optical density (OD) values in the skin and low OD values in the core. As the heat treatment temperature was increased, the OD of the pre-oxidized fibers increased, which is because of the formation of C = O, C = N, C = C, and their conjugated structures of C = N with C = C. The difference in the OD values between the pre-oxidized fiber skin and core became increasingly apparent as the heat treatment temperature increased, with the OD difference increasing from 0.045 at 220 °C to 0.085 at 260 °C. The OD difference is closely related to the oxygen element and C = O functional groups in the fiber. The contents of the oxygen element and C = O in the pre-oxidized fiber skin were higher than those in the pre-oxidized fiber core. At a heat treatment temperature of 260 °C, the relative content of C = O in the skin was 0.454, whereas that in the core was 0.313, which was consistent with the trend of the OD value change. In comparison, C = C and C = N formed during pre-oxidation were not substantially distributed in the radial direction of the fibers. The radial inhomogeneity of the pre-oxidized fiber was mainly affected by the radial difference of the carbonyl content.

This study examined the natural dyeing properties of hemp fabrics using a mixed mordant consisting of aluminum potassium sulfate (10 and 20 g/L) and tannic acid (5 and 10 g/L). The natural dye was derived from jackfruit wood (Artocarpus heterophyllus) and then processed into a powder via spray drying. The fabrics were dyed using 10% owf dye, at a pH of 5, temperature of 80 °C, for 50 min, with a liquor ratio (L:R) of 1:30. Prior to dyeing, mordanting was applied to improve dye uptake. The mordanting process compared three distinct heating techniques: infrared heating (IRH), ultrasonic heating (USH), and microwave heating (MWH). The X-ray diffraction results showed that MWH was the only heating technique that maintained the crystallinity index ((CI)) of the fibers. However, it produced slightly lower color strength ((K/S) of 1.01 ± 0.01) compared to IRH ((K/S) of 1.36 ± 0.04) and USH ((K/S) of 1.32 ± 0.04). IRH exhibited the most significant reduction in the (CI), followed by USH. The sample treated with IRH had the highest aluminum content (0.88 ± 0.02%), whereas the MWH-treated sample had the lowest (0.75 ± 0.02%), which is consistent with the results concerning (CI) and (K/S). The ratings for color fastness to washing, light, and rubbing were generally favorable. Mordanting enhanced both the color fastness and the color strength of the fabric, but it did not affect the tensile properties of the fabrics. Mordanting and dyeing slightly enhanced the ultraviolet protection efficiency of the fabrics. However, all samples, including the pristine hemp fabric, provided excellent protection against ultraviolet radiation.

Graphical Abstract

Thermoplastic polyurethane (TPU) is a highly favored polymer for 3D printing materials due to its excellent impact and abrasion resistance, superior mechanical properties, and flexibility at low temperatures. Enhancing TPU with conductivity considerably broadens its application range, paving the way for its use in advanced flexible electronics, wearable technologies, and improved industrial components. The addition of electrically conductive fillers such as multi-wall carbon nanotubes (MWCNTs) can improve the conductivity of TPU. In this study, we synthesized TPU with a bio-based polyol (polytrimethyleneether glycol) and chain extender (1,3 propanediol) and improved its conductivity by adding a small amount of CNTs via in situ polymerization without using any harmful solvents. The CNT content was varied from 0.75 to 3.75 wt% and to achieve a tensile strength of 13.45 ± 0.3 MPa, a maximum elongation at break of 859% ± 6%, a hardness of 77 ± 2 Shore A, and the highest conductivity (2.26 × 10⁻⁴ S/cm) with 3.75 wt% of CNTs. Because these physical properties are sufficient for 3D printing, the TPU/CNT composites developed herein can be promising in applications requiring conductive materials.

Several effective methods to precisely evaluate the comfort of hygroscopic cooling fabrics transitioning from a wet to dry state were previously lacking. This study employed the heated plate method to mimic bare skin. We integrated a refitted YG606 II Thermal Resistance Tester with a heating control unit to simulate the human body’s thermoregulation following light activity at a basal metabolic rate. This apparatus recorded the heating curves of hygroscopic cooling fabrics in their wet state to monitor temperature variations during drying. We introduced five objective evaluation parameters (Area, FWHM, K₁, K₂, WCI) based on the temperature differences between the heated plate and wetted fabric samples to differentiate levels of wet comfort among various fabrics. Twelve types of hygroscopic cooling fabrics, varying in material, structure, and hygroscopic properties, were selected from the market to assess the reliability of these parameters. The findings confirmed that these parameters effectively discern variations in wet comfort across the fabric samples. The parameters for cooling capacity (Area) and cooling rate (K₁, K₂) are critical in evaluating the role of liquid water in fabric on wet comfort, while cooling duration assesses the impact of the fabric’s drying process on human comfort. Furthermore, the wet comfort index (WCI) correlated significantly with perceptions of dampness and coldness; a higher WCI value indicated a sharp, transient discomfort due to dampness and coldness, whereas a lower value suggested a mild, sustained sensation of wetness and coldness. The preference for these contrasting sensations varies by context. This research could facilitate the development of predictive models for wet comfort by evaluating the cooling capacity and wet comfort index of textiles in their wet state, thereby aiding fabric researchers and manufacturers in enhancing the thermal–wet comfort of hygroscopic cooling fabrics.

Shear thickening fluid (STF) is a solution performs an increase in its viscosity under shear stress. This study investigates rheological behavior of STF, then its effectiveness against dynamic loadings for the case it is applied on aramid fabric. Polyethylene glycol 200 and 400 g/mol, and Aerosil 200, 300, 380 were used for preparation of STF. Rheological analysis was performed to determine thickening behavior and parameters for the solutions having 5, 10 and 20% silica concentrations by weight. The solution having optimum shear thickening performance for dynamic impact loading was selected and it was impregnated aramid fabric to prepare low velocity impact and ballistic test samples. Low velocity impact experiments were executed for different number of layers from 1 to 8 at different energy levels to obtain absorbed energy and maximum contact force values. A curve fitting equation was derived for absorbed energy and number of layers of aramid fabric. Finally, Level IIA ballistic test was done to test whether the curve fitting equation is effectively working or not. Additionally, STF impregnated aramid fabric with its neat counterpart against ballistic impact was compared. A detailed ballistic test characterization was performed including the last shape of ammo. It is determined that impregnation of STF has important effects on ballistic behavior of aramid fabric.

With the rapid development of the economy, new imitation methods are keeping emerging and posing a huge challenge to anti-counterfeiting technology. Due to the advantages such as good concealment, high recognizability, water repellency, and dirt resistance, fluorescent fiber has attracted great attention from researchers. To impart good fluorescence to chitosan (CS) for the preparation of anti-counterfeiting fiber, various amounts of fluorescent molecules — carboxyl-containing spiropyran (SP)—were used to label CS to prepare a series of CS–SP with different degrees of labeling (DL). Then, nanofiber membranes were produced by electrospinning using the CS–SP/PVA blend spinning solutions. Effects of the DL on application performance of the CS–SP were studied. It was found that, labeling appropriate amounts of SP units onto CS was an effective way to endow the CS with good fluorescence property. With the increase in the DL of the CS–SP, its fluorescence intensity increased initially, reached the maximum when the DL was 0.499 mol%, and then decreased. At the DL of 0.499 mol%, the CS–SP/PVA nanofiber membrane could emit bright fluorescence, of which the color was able to change dynamically along with the irradiation time of UV light. Meanwhile, the labeling of SP unit would not bring about adverse effects on surface morphology of the electrospun CS–SP/PVA nanofiber membrane. The fluorescent CS–SP nanofibers have overcome many shortcomings of the commonly used fluorescent fibers and shown great application potential in the anti-counterfeiting field.

Aggregation-induced emission (AIE) technology had already been applied in polymer science and provides a deeper understanding on polymer structure and formation processes. Here we prepared a copolymer of (2-(4-vinylphenyl)ethene-1,1,2-triyl)tribenzene (TPEE) and acrylonitrile (AN) (PTPEE-co-AN), which was utilized as the fluoresce probe for the monitoring of the electrostatic spinning process. Owing to the physical entanglement which restrincted the movement of TPE units, the PL intensity of the spinning solution increased with the increase of PAN in the solution. The viscosity and the concentration of PAN spinning solution was, therefore, could be monitored by PL intensity or by nake eyes. As the main component of fluoresce probes was PAN, the copolymer can be well integrated with spinning components, and has no impact on the electrospinning process. Moreover, the PTPEE-co-AN endowed photoluminescence properties to the formed fibers, as well as the fiber films. This method provides a new observation platform for the electrospinning process, and a variety of probes can be prepared through copolymerization to suit the spinning of different polymers.

This study investigates the mechanical properties of composites focusing on tensile, flexural, compression strength, Izod impact toughness, hardness, fatigue life, creep resistance, and drilling behavior. The approach involves extracting nano-biosilica from sorghum husk and infusing it with silane-treated kenaf fiber under temperature aging conditions to enhance composite materials’ properties. The reinforcement consists of kenaf fibers (34.2–43.2 µm in diameter) and nano-biosilica prepared from sorghum millet husk via a thermochemical method. Silane treatment enhances the adhesive bonding between the matrix (vinyl ester resin and methyl ethyl ketone peroxide in a 10:1 ratio) and reinforcing agents. Composite fabrication employs a hand layup method with varying concentrations of biosilica (1 vol. %, 3 vol. %, and 5 vol. %) and kenaf fiber. Notably, specimens N2 and M2 exhibited superior performance, with N2 achieving tensile strength of 101 MPa, flexural strength of 123 MPa, compression strength of 159.9 MPa, Izod impact toughness of 4.9 kJ/m², and hardness of 98 Shore-D. Even after undergoing aging at 40 °C and 70% humidity for 30 days, M2 demonstrated remarkable durability to the silane treatment of both fiber and filler with tensile strength of 85 MPa, flexural strength of 117 MPa, compression strength of 143 MPa, Izod impact toughness of 4.2 kJ/m², and hardness of 95 Shore-D. SEM analysis revealed uniform dispersion of filler particles in N2 and M2, highlighting the effectiveness of the silane treatment in enhancing microstructural characteristics and durability. This research underscores the potential of silane-treated kenaf-fiber- and nano-biosilica-reinforced vinyl ester composites for applications requiring enhanced mechanical properties and durability.

Nowadays, composite materials are widely used in various industries, including aerospace, automotive, and military sectors. In many of these applications, there is a need to understand the dynamic and vibrational responses due to changes in different parameters for a more precise structural analysis. This study examines the impact of varying fiber types under different boundary conditions on the natural frequency of a three-dimensional woven composite rectangular plate. For this purpose, the Ritz theory has been used to calculate the system’s natural frequency, and to validate the results, the current analysis method has been compared with previous research findings and results from finite element software simulations. The results obtained from the analytical solution and finite element simulation correlate well.