Fibers and Polymers最新文献

This study aims to optimize the thermo-mechanical properties and shape-memory effect of twisted nanofibrous yarns featuring a core–shell structure for potential integration into thermo-responsive smart textiles via conventional processing methods, such as weaving and knitting. Twisted shape-memory polyurethane (SMPU) yarns were fabricated utilizing a double-nozzle electrospinning device, and the effects of twist amount and core–shell configuration on their structural, mechanical, and shape-memory properties were examined. Morphological analysis confirmed the production of uniform yarns with twist angles ranging from 7 to 21°, while differential scanning calorimetry (DSC) thermograms indicated a transition temperature of approximately 44 °C. Increased levels of twist resulted in a significant rise in maximum stress, approximately 36%, alongside an enhancement in Young’s modulus of about 30%, with elongation at break values within the range of 140% to 180%. The thermo-mechanical behavior was assessed at 50% and 100% strain over three cycles, demonstrating improved shape fixity and recovery with increased twist levels. Although exhibiting lower mechanical strength, core–shell yarns displayed comparable shape-memory performance to their single counterparts. These findings contribute valuable insights into the optimization of electrospun yarn structures for enhanced shape-memory functionality in the context of smart textiles.

Biodegradable and affordable jute fibers absorb too much moisture, limiting their use. This research improves these fibers' moisture and water resistance to boost their utilization in many fields of application. The combined impact of chemical treatments and gamma irradiation improves moisture and water resistance properties. This study has determined the hydrophilicity of jute fibers by moisture content, moisture regain, water absorption, and water contact angle. Lower moisture levels make jute fibers stronger and less fragile. Jute fibers with reduced moisture content last longer and degrade less. The results indicate that the combined impact of irradiation and treatment on jute fibers resulted in a substantial increase in crystallinity, with a 31.27% increase. Additionally, the water contact angle significantly improved by 97%, and moisture contain, regain, and absorption reductions occurred by 60%, 63%, and 45%, respectively. These results suggest that the combined treatment significantly enhances the resistance to degradation of jute fibers, rendering them appropriate for use in humid environments. Jute fibers resist water better, improving dimensional stability and decreasing swelling and shrinkage. Reduced water absorption minimizes the risk of rot, mildew, and other biological degradation, extending the lifespan of jute fibers and products. Jute fibers resist water better, improving dimensional stability and decreasing swelling and shrinkage. Reduced water absorption minimizes the risk of rot, mildew, and other biological degradation, extending the lifespan of jute fibers and products. The treated fibers' moisture content and water absorption decreased significantly, improving dimensional stability, swelling, and biological deterioration. Water resistance increases fiber strength and durability, making them more suitable with composite materials and matrix bonding. Thus, treated jute fibers have improved mechanical characteristics and are better for high-performance applications, including textiles, construction, automotive, and environmental remediation. This modification method makes jute fibers useful in moisture-sensitive areas and sustainable and durable composite products.

Voids are a common defect in the manufacturing process of composite materials, which can reduce the mechanical properties of components. As an out-of-autoclave (OoA) technology, double-vacuum-bag (DVB) process can achieve low-cost manufacturing of composite materials with low void content. This paper investigated the effect of DVB process on void evolution and laminate properties during the curing process of composites. Different dwelling temperatures were applied, and a single-vacuum-bag (SVB) process was designed as the experimental control group. The curing cycles were completed and the laminates were rapidly cooled at selected time points. This work used a microscope to take cross-sectional images of samples, for statistical analysis of void morphology and void growth behavior. Besides, the density and fiber volume fraction of composite materials were measured by Archimedes method and combustion method. The experimental results show that as the curing cycle progressed, the void content of laminate produced by DVB process continued to decrease. Compared with the SVB process, the dual vacuum environment of the DVB process can timely discharge the stagnant air in the prepregs, thereby reducing the void content, which is at the same level of the composite materials manufactured by hot press with 0.6 MPa.

The poly(N-isopropylacrylamide) (PNIPAM) and cellulose acetate (CA) hydrogels were synthesized both in the presence and absence of N,N(^prime)-methylenebis(acrylamide) (NMBA) as a crosslinker. In the absence of NMBA, chemical crosslinking between PNIPAM and CA was demonstrated through free radical polymerization in acetone as the solvent, which has not been reported previously. These hydrogels exhibit smaller swelling ratios (2 to 22 water grams per xerogel gram) and larger compression moduli (from 0.39 to 2.62 MPa) than homo NIPA hydrogels. The lower critical solution temperature (LCST) values for these hydrogels increased from a range of 38 to beyond 50(^circ)C, depending on the CA concentration, and were higher than those of homo PNIPAM hydrogels. The formulations with 50 wt.% solids and 10 and 15 wt.% CA were barely affected in their swelling capacity when heated to 50(,^circ)C. These hydrogels were used to remove (hbox {Ni}^{2+}) from aqueous solutions. The adsorption capacity of these hydrogels ranged from 2 to 38 mg of (hbox {Ni}^{2+}) per gram of xerogel. The hydrogels synthesized without NMBA, exhibited typical PNIPAM LCST values, so they were used to adsorb (hbox {Ni}^{2+}) in solution and release it through the shrinkage process. When these hydrogels were reused four times in a row, the removal efficiency averaged 80% for each use and the overall remotion of (textrm{Ni}^{2+}) ranged from 97 to 151 mg per gram of xerogel. A potential application for cleaning polluted waters with (hbox {Ni}^{2+}) using PNIPAM-CA hydrogels is proposed herein, the cost of producing 1 g of these hydrogels in laboratory conditions is approximately 3 USD.

PET recycling is one of the most successful examples of polymer recycling. This study explored the mechanical recycling of PET bottles to produce industrial-grade PET fibers. Recycled bottle-grade PET (rPET) underwent solid-state polymerization at 230 °C to increase molecular weight (MW), followed by melt spinning at 300 °C. The weight-average MW reduction rates for virgin PET (vPET) and rPET with the same intrinsic viscosity were nearly identical. However, rPET fibers exhibited lower tensile strength and higher shrinkage rates than vPET fibers at the same draw ratio, primarily due to the presence of IPA units in the rPET structure. Using rPET polymerized to higher MW, the tensile strength of rPET fibers comparable to vPET fibers could be produced. Under UV irradiation, vPET and rPET fibers showed similar trends in tensile strength loss and MW reduction. UV irradiation predominantly affected the amorphous regions of the PET fibers, with minimal impact on the crystalline areas. This study demonstrates the feasibility of producing industrial PET fibers from rPET through SSP and melt spinning, offering a sustainable approach for high-value applications.

The current work describes the development of silica chitosan-guar gum blended nanocomposites (NCs) for the proficient removal of mercury (Hg²⁺) ions in aqueous solution at pH 12. The silica NCs were prepared by dispersing the as-synthesized silica nanoparticles (NPs) into the chitosan-guar gum (CS-GG) polymer blend matrix. The developed silica NCs were characterized by FTIR, SEM–EDS, XRD, TGA, and BET. The results confirmed the dispersion of silica NPs on the surface of the CS: GG blend resulting in silica NCs with improved thermal stability, and an enhanced specific pore surface area from 11.843 m²/g to 23.029 m²/g. The 2 and 5% silica NCs were used as an efficient adsorbent for the removal of mercury ions. The 2 and 5% of silica NCs showed a maximum removal efficiency of 88% and 79% for mercury ions, respectively. The adsorption process is best fitted with the Langmuir adsorption isotherm and pseudo-second-order kinetic model. The adsorbent proved to be economical with 72% of removal efficiency after five cycles using EDTA as a desorbing solution.

Fly ash (FA) is a byproduct of coal combustion, particularly in coal-based power plants. If FA is released into the open atmosphere or land, it becomes a major source of air and water pollution. The impact of FA on woven glass fabric-phenolic composite laminates is examined in the present study to find the application of FA in the structural field. The hand layup method is used to apply the FA-phenolic resin slurry (0 to 20 wt% FA) onto the woven glass fabric surface, followed by compression molding to get composites. The viscoelastic and static mechanical properties are evaluated using a dynamic mechanical thermal analyzer and a universal testing machine. The results show significant improvement in the flexural strength (26%), flexural modulus (31%), storage modulus (37.9%), and loss modulus (44%) of FA-GFRP composites. The interfacial interaction parameters such as entanglement density, reinforcing efficiency factor, and adhesion factors (b and C-factors) are also evaluated and correlated with other properties to understand the impact of FA on the performance of FA-GFRP composites.

The effect of chemical treatment on the surface modification and pulverization of coir and banana fibres was investigated in this study. Caustic soda, silane, and potassium permanganate treatments were chosen to remove the non-cellulosic contents (i.e., lignin, hemicellulose, wax, etc.) as well as to improve the pulverization of banana and coir fibres during the ball milling. Surface morphology and mechanical characteristics of coir and banana fibres were compared before and after the chemical treatments. The chemical treatment was found beneficial for the easier defibrillation of banana and coir fibres during ball milling. Among all the chemical treatments, the silane treatment was found more effective to get smaller size of particles with narrow particle-size distribution. This behaviour was attributed to the hydrophobic characteristics of the silane-treated fibres, which pulverized effectively to particles without forming fibre lumps rolling inside the milling container. The approximate particle size of untreated coir fibres was 2200 nm, which reduced to 788 nm with NaOH treatment, 413 nm with KMnO₄ treatment, and 496 nm with silane treatment after 90 min of pulverization. Similarly, the particle size of untreated banana fibres was 922 nm, which reduced to 777 nm with NaOH treatment, 426 nm with KMnO₄ treatment, and 223 nm with silane treatment.

This study investigated the dyeability of poly(ethylene terephthalate-co-polyethylene glycol) (PCP) fibers engineered for convenient disperse dyeing, using both low and high energy disperse dyes within a temperature range of 90–130 °C. A thermodynamic analysis revealed that the disperse dyeing of PCP fibers followed the Nernst isotherm. It displayed higher partition coefficients and equilibrium exhaustion than those of conventional PET fibers. The affinity parameter indicated a higher affinity of the disperse dyes for the PCP fibers, although the enthalpy and entropy variation indicated weaker dye embedding within the PCP polymer matrix. Kinetic studies revealed that dye exhaustion occurs more rapidly on PCP fibers at a temperature below the conventional disperse dyeing temperature for polyester (i.e., below 130 °C). In addition, the PCP fibers exhibited lower dyeing transition temperatures and higher diffusion coefficients at these reduced temperatures. Among the studied dyes, the low-molecular-weight disperse dye demonstrated more favorable thermodynamic and kinetic parameters than the high-molecular-weight disperse dye. Overall, these observations indicate that dyeing at 100 °C under atmospheric pressure is the optimal process condition for PCP fibers and is effective for both low- and high-molecular-weight dyes.

The objective of this work is to create an ABAQUS plugin for predicting the failure mechanism, and mechanical characteristics of weft-knitted reinforced composites utilizing multi-scale modeling. This plugin facilitates the automatic modeling and analysis of weft-knitted reinforced composites, focusing on parameters such as stiffness, strength, and failure mechanisms. The developed plugin estimates the homogenized effective elastic properties of a user-created macro-model for a weft-knitted reinforced composite structure. The plugin correctly extracts the concepts of homogenization based on micromechanics parametric inputs of fiber and resin which are considered separately by the software’s user. Afterward, the homogenized constants of the composites are automatically applied to the macro-model to achieve the most susceptible areas for failure after the localization step. It also enables the prediction of the composite strength and the identification of the sample’s critical mesoscale regions. This paper also explains the plugin’s homogenization and localization-based approach. Prior to carrying out parametric research, the simulation findings are verified using experimental data. Furthermore, experimental instances demonstrating its implementation and validation are provided. A comparative analysis of tensile characteristics between the multi-scale finite element model and experimental results disclosed that the model exhibited an overestimation of the failure strength in the course and wale directions by approximately 13%. Furthermore, the error due to predicting the tensile modulus in both directions is less than 7%. The results obtained from the prediction of the plugin revealed the approximate locations of failures within the composite unit cell under tensile loading in both course and wale directions.