Polyamide Fibers Research Articles

Printability and mechanical behaviors of continuous polyamide fiber reinforced polycaprolactone composites

Printability and mechanical behaviors of continuous polyamide fiber reinforced polycaprolactone composites

Magnetic Effects in Textile Fibers Filled with Nanoconstituents Based on Iron Oxides

ABSTRACT The paper proves the possibility of providing magnetic properties in the process of saturation of textile fibers with a nanomixture of divalent and trivalent iron oxides. The mechanisms of interaction of nanostructures with natural and synthetic fibers are analyzed. The peculiarities of the introduction of magnetic components into flax, cotton, polyamide, and polyester fibers are determined. The relative number of particles with nanoscale in the total was statistically proved. To evaluate the macro effects of saturation, the relative amount of the accumulated mixture of divalent and trivalent iron oxides was determined, taking into account the previous fiber weight. Two basic constants characterizing the properties of textile fibers to magnetic interaction are proposed. It is proved that flax fibers exhibit the highest magnetic efficiency. The average size of iron oxide nanoparticles is 80–90 nanometers, which is confirmed by studies using electron microscopy. The final magnetization of the obtained textile materials provides an attractive magnetization of 20–30 mPascal. The magnetic field of magnetic textile fibers acts at a height of up to 6–7 mm. The directions of the use of fibers with magnetic properties are shown as a prospect for the development of textile smart products.

Preparation and melt-spun applications of PA6-based Poly(Amide-Ether) copolymers phase change fibers with passive temperature management

Phase change fiber, as an intelligent fiber material used in passive thermal management, can balance the temperature of the microenvironment near human skin. However, the traditional blending method makes phase change material prone to leakage during the processing and applications. Herein, this work introduces the phase change material PTMEG into the polyamide 6 (PA6) chain through melt polymerization to prepare a series of PA6-based poly(amide-ether) copolymers. Copolymers exhibit an obvious microphase separation structure, with the PA6 segments and the PTMEG segments can form independent crystalline and amorphous regions. PTMEG in copolymers through polymerization method exhibits better thermal stability compared with the blended way, which effectively solves the leakage problem of phase change materials. The copolymers can be directly melt-spun (1500 m/min) to prepare PA6-based phase change fibers. The fiber can maintain excellent mechanical properties (breaking strength of 2.12 cN/dtex). Meanwhile, the crystallization enthalpy and melting enthalpy of the PTMEG in the fiber are 10.59 J/g and 12.44 J/g, respectively. The thermal management time of the fiber in the hot environment is 349 s, and the maximum temperature difference is lower 5.6 ℃ from the PA6 fiber. In addition, the exothermic duration in a cold environment is 536 s, and the maximum temperature difference is higher 1.1 °C from the PA6 fiber. Meanwhile, the thermal enthalpy of the fiber remained stable (fluctuation within 2 %) after 20th thermal cycles, and the loss rate is less than 2 % after washing at 25 ℃, 50 ℃ and 90 ℃. The fiber exhibits good thermal stability, water washability and cyclic stability. Preparation of high enthalpy polymers directly by copolymerization will provide new ideas for phase change fibers for apparel.

Extrusion and Injection Molding of Polyethylene Loaded with Recycled Textiles: Mechanical Performance and Thermal Conductivity

The aim of this project was to assess the thermal conductivity of polyethylene (PE) filled with carbon black (CB), specifically for geothermal pipes. The project explored the potential modification of PE’s thermal conductivity by incorporating recycled textile fibers. Different types of shredded recycled fibers were tested, including two types of polyamide fibers with varying contaminations and one type of polyester fiber. Following several preparation steps, various composite materials were manufactured and compared to bulk PE using various testing methods: Differential Scanning Calorimetry analysis (DSC), mechanical testing (flexural and tensile), and laser flash analysis (LFA). The results revealed alterations in the mechanical properties of the composite materials in comparison to PE filled with CB. The LFA tests demonstrated the effectiveness in reducing polymer thermal diffusivity at higher temperatures, particularly when the material was loaded with recycled polyester fillers.

Developing Approaches to Optimise Reparative Histogenesis of the Tympanic Membrane Tissues: History, the State-of-Art and Perspectives of Reparative Otosurgery

The paper describes the issues to optimize reparative histogenesis of the tympanic membrane tissues (history, state-of-the art and perspectives) based on data from national and foreign scientific literature. One of the causes of hearing loss is the violated integrity of the tympanic membrane, resulting from its injury or the developing inflammatory processes in the middle ear. It has been established that small perforations of the tympanic membrane can spontaneously close in the reparative stage of acute purulent otitis media or when the exacerbation of chronic purulent otitis media subsides. Restoration of large perforations of the tympanic cavity requires surgical intervention. Since 17th century, plastic surgery options for the tympanic membrane perforations with various biological and non-biological materials have been developing. However, until the beginning of the XX century, the approaches used did not lead to complete histio- and organotypic restoration of the tympanic membrane, but only ensured closure of the defect. At the present stage, otosurgeons use various plastic materials to restore the integrity of the eardrum: autografts; allografts; implants made of non-biological material. Nylon mesh, cotton-adhesive discs, and knotless knitted fabric made of polyamide fiber are applied as implants. Biological transplants applied include the skin of the inner surface of the shoulder and the occipital-temporal region, the wall of the vein, the fascia of the temporal muscle, the dura mater, the perichondrium, nanostructured bioplastic material created on the basis of hyaluronic acid hydrocolloid and a peptide complex, etc. The use of these modern options in most cases leads to organotypic and, in some cases, histiotypic restoration of the eardrum structure, ensuring complete epithelialization of its outer and inner surfaces. However, there are a number of unresolved issues regarding the diverse materials application for plastic surgery, as well as the timing of reconstructive surgeries on the middle ear.

Enhancing the performance of 3D-printed fiber-Reinforced mortar: synergistic effects of clays and bacterial cells as viscosity modifying agents

The absence of standardized 3D concrete printing mixtures drives ongoing material exploration. This study investigates mineral and bio-based viscosity modifying agents (VMAs) application in fiber-reinforced cementitious mortar. Nano-montmorillonite, sepiolite, and bacterial cells function as supplementary materials, partially substituting cement with fly ash for sustainability assessment and compatibility evaluation in our study. Mechanical tests encompass compressive, flexural strength, and interlayer bonding in 3D-printed samples. Based on the results, incorporating 0.150% Polyamide (PA) fiber positively affected interlayer bonding strength and deceleration of the flow loss rate. Additionally, adding clays decreased workability and compressive strength but improved interlayer bonding and flexural properties. On the other hand, substituting 20% of cement with FA improved the flowability of the mixture and showed great compatibility with other materials during printing. Applying a cement paste layer was evaluated as a practical method for bond enhancement at the interface. Bacteria incorporation improved flexural strength but weakened interlayer bonding. However, the combination of bacteria and clays resulted in a superior improvement in mechanical properties. This study demonstrates clays and bacteria’s potential in enhancing rheological and mechanical features in cementitious fiber-reinforced mortar. Notably, this study introduces bacteria cells and sepiolite as rheology modifiers in 3D concrete printing for the first time. Additionally, it presents a novel dog-bone-shaped structure test for assessing interlayer bond performance.

Synergy performance of hybrid fiber-reinforced ultra-high-performance cementitious composites with low fiber contents

This study aims to assess the synergistic tensile performance resulting from the hybridization of long and short fibers. Three types of long steel,fibers, i.e., twisted, hooked, and smooth fibers, along with two types of short fibers, i.e., smooth and polyamide fibers, were incorporated into ultra-high-performance concrete (UHPC) at a total volume content of 1.5%. To predict the tensile resistance of the hybridizations, various machine learning models, including artificial neural network (ANN), decision tree (DT), random forest (RF), and support vector machine (SVM), were applied by utilizing a significant number of collected experimental results. Experimental findings demonstrated that the hybridization of long and short fibers effectively enhanced tensile resistance compared to mono fibers. These hybridizations exhibited negative synergy factors in post-cracking strength but positive synergy factors in both strain capacity and specific work to fracture. Predictions using machine learning models revealed that the RF model exhibited outstanding performance in predicting the tensile resistance of the hybridizations. Furthermore, the compressive strength of the matrix was found to be the most important factor affecting post-cracking strength, whereas fiber length had the most substantial impact on the strain capacity.

Kinetics of Radiation-Oxidative Aging of Polyamide Fibers and Composites Based on Them

Kinetics of Radiation-Oxidative Aging of Polyamide Fibers and Composites Based on Them

Influence of Flow-Induced Polymorphism and Fiber Morphology on Mechanical Behavior in Long Discontinuous Glass Fiber Polyamide Composites

This study investigates the combined flow-induced crystallization in the polymer and fiber reorientation during compression molding of a long discontinuous glass fiber polyamide (PA 6) composite. The composite is molded from an organosheet (a semi-finished pre-impregnated mat); the composite anisotropic tensile properties are evaluated as a function of polymer crystalline morphology and fiber orientation state, both controlled by the extent of material flow in the mold. To study these effects, the full mold coverage and partial center charge of organosheet (OS)-80 %, 60 %, 50 %, and 40 % were compression molded to cause varying anisotropic material flow. Tensile specimens were cut out from the molded plates in the flow and transverse direction and tested to compare their effective tensile properties (modulus and strength). The flow-induced morphological changes in a molded composite at the glass fiber bundle microstructure scale and polymer crystalline phases nano-structure were characterized using optical microscopy and X-ray diffraction, respectively. These morphological changes contributed to the significant change in the tensile strength and modulus; a combined experimental/numerical simulation framework was used to segregate the relative contribution of each factor. Experimentally, the tensile modulus increased in the flow direction from 9.6GPa to 14.9GPa for the specimens produced by full mold coverage and OS-50 % coverage mold, respectively. The tensile strength increased from 162 MPa to 254 MPa for the full and OS-60 % mold coverage. On the contrary, the strength and modulus in the transverse direction to the flow showed a significant drop to 35 MPa and 3GPa, respectively, which was attributed to reduced fiber alignment and anisotropy in the PA6 matrix.

Development and application of a novel extraction protocol for the monitoring of microplastic contamination in widely consumed ruminant feeds

Plastics and, in particular, microplastics (MPs) (< 5 mm) are emerging environmental pollutants responsible for interconnected risks to environmental, human, and animal health. The livestock sector is highly affected by these contaminants, with 50–60 % of the foreign bodies found in slaughtered domestic cattle being recognized as plastic-based materials. Additionally, microplastics were recently detected inside ruminant bodies and in their feces. MPs presence in ruminants could be explained by the intensive usage of plastic materials on farms, in particular to store feeds (i.e. to cover horizontal silos and to wrap hay bales). Although feed could be one of the main sources of plastics, especially of microplastics, a specific protocol to detect them in ruminant feeds is not actually present. Hence, the aim of this study was to optimize a specific protocol for the extraction, quantification, and identification of five microplastic polymers (high-density polyethylene, low-density polyethylene, polyamide fibers/particles, polyethylene terephthalate and polystyrene) from feeds typically used in ruminant diets (corn silage, hay, high protein feedstuff and total mixed ration). Several combinations of Fenton reactions and KOH digestion were tested. The final extraction protocol involved a KOH digestion (60 °C for 24 h), followed by two/three cycles of Fenton reactions. The extraction recoveries were of 100 % for high-density, low-density polyethylene, polyamide particles, and polystyrene and higher than 85 % for polyethylene terephthalate and polyamide fibers. Finally, the optimized protocol was successfully applied in the extraction of microplastics from real feed samples. All the feeds contained microplastics, particularly polyethylene, thus confirming the exposure of ruminants to MPs.

Altering the percolation threshold of PA66‐copper hybrid in an electroless copper deposition process by surface activation of the polymer

AbstractIn this study, the impact of three different principles of surface activation techniques for polyamide fibers on the formation of conductive percolation during the subsequent electroless copper deposition process was investigated. The techniques used are (1) polyamide complexation using a solution mixture of calcium chloride, ethanol and water, (2) atmospheric plasma surface treatment and (3) grafting of 2‐hydroxyethylmethacrylate by radical induced polymerization. As a result, the percolation threshold was shifted to lower copper contents. The copper content required to form conductive structures was reduced ranged between 59% and 89%, depending on the activation techniques. Furthermore, the deposition time was reduced by 37%–57%, resulting in a faster build‐up of the percolation on the fabric. Changes in wetting behavior and substrate surface topography were identified to be the main reasons for these observations. While all applied surface activation techniques led to higher copper contents compared to unmodified reference, the atmospheric plasma modification led to the highest copper contents during the deposition process and a more uniform appearance of the metallised layer.Highlights Three different fiber surface activation methods are evaluated. Fiber surface activation increases wetting and polymer‐metal adhesion. Activated polymer surface leads to faster copper deposition and percolation. Atmospheric plasma modification is the most efficient technique.

MODERN APPROACHES TO THE USE OF COMPOSITE MATERIALS IN CONSTRUCTION

A review of the literature on scientific approaches in the development of composite materials and building structures made of composites is carried out. When creating and manufacturing traditional and new composite materials, for example, by additive manufacturing, and when creating structures and structures in engineering calculations, new techniques, finite element computational software systems, and neural network technologies are used, which are used in the creation of modern metal and composite materials, analysis of mechanical characteristics of materials, forecasting loads on the structure, optimization of structures and calculation of their construction characteristics. The distinctive features of modern composite materials are shown. The main types of composite materials are considered: talc, diatomite, calcium carbonate, gibbsite, barium sulfate, feldspar, nepheline, aragonite, calcium carbonate, wool, silk, cotton, linen, jute, wood pulp, asbestos, fiberglass, metal fibers, quartz fibers, basalt fibers, polyamide fibers, polyester fibers, polyvinyl alcohol fibers, carbon fibers, viscose fibers. The physical and mechanical characteristics of composite materials (based on epoxy, aluminum, carbon, magnesium, and nickel matrices) and traditional (steel, aluminum, brick, concrete) building materials are presented. The disadvantages of such composite materials as carbon fiber, fiberglass, organoplastics, textolite, carbon concrete, and polystyrene concrete are presented. Deformation diagrams of some types of fibers for composite materials are considered: high-modulus carbon fibers, high-strength carbon fibers, aramid fibers, glass fibers, and basalt fibers. The advantages of the system of external reinforcement of building structures with composite materials are described. Examples of reinforcement of building structures are considered: reinforced concrete reinforcement; reinforcement of floor slabs; reinforcement of columns; and reinforcement of brick walls.

Prevalence of Microplastics in Coastal Area of Samae San, Thailand and Its Possible Source

This research explored the abundance, morphology, and polymer composition of microplastics (MPs) in various environmental samples within the Samae San subdistrict involving surface soil nearby the dumping site, road dust soil, beach sand and sediment in the area with distinct land- based activities. Dumping site soil exhibited the highest concentration in items per kg of dry weight at 93,734.3, followed by road dust soil (573.0 ± 583.7), beach sand (99.8 ± 75.3), and sediment (83.1 ± 50.4). Morphological traits revealed similarities between transparent fiber-shaped particles in beach sands and sediment, and those in nearby road dust soil, while green sheet-shaped particles dominated in dumping site soil. Predominant polymer types included PE, PET, and PP, associated with daily plastics, fishing gear, and fishing nets. In beach sand and sediment samples, transparent polyamide (nylon) fibers shaped like microplastics (MPs) were notably observed, as it is a common material used in fishing nets. Cluster analysis indicated a resemblance between MPs in beach sand, sediment, and nearby road dust soil, implying that plastic debris, comprising single-use plastics and fishing equipment, could be a potential source of MPs in coastal areas.

Mussel-inspired fabrication of nonwovens using fluoride-free profiled fibers for directional water transport

Fabrics with directional water transport performance have attracted considerable attention in daily life. They are in high demand, owing to their ability to transport sweat away from the skin to improve personal comfort. However, the fabrication of such materials has still remained a critical task. This article reports a nonwoven with the directional water transport function, achieved using a synergistic combination of a microstructure and a wettability gradient. The three-step fabrication strategy involves needling bonding of Y cross-section polyamide fiber webs with two needling densities (30 and 190 needle/cm2), followed by single-sided spraying of polydopamine–silicon carbide powder–polyethyleneimine dispersion and a fluoride-free hydrophobic agent. Using fiber webs with different needling densities endows the nonwoven fabric with a differential capillary effect, enhancing the directional water transport property. The unique microstructure achieves the directional water transport property by improving permeability at lower needling densities and hindering transport through a denser needling density in the reverse direction. At the same time, the wetting gradient effect promotes water transfer from the hydrophobic surface to the hydrophilic surface. The successful preparation of these interesting directional water transport materials offers new insights into the role of fibrous materials, the needling density of nonwovens, and the development of highly comfortable moisture-wicking textiles.

Discrete molecular weight strategy modulates hydrogen bonding‐induced crystallization and chain orientation for melt‐spun high‐strength polyamide fibers

AbstractHydrogen 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.

Tribological and mechanical characterization of glass fiber polyamide composites under hydrothermal aging

Polymer composites are increasingly used in applications where they are subjected to abrasive wear. The bulk of prior research has focused on the performance of polymers under sliding wear conditions and in some cases resulted in a contradiction, particularly when it comes to the effect of reinforcing fibers on the wear performance. Another omission is the absence of pre-conditioning or accelerated aging which is clearly an important factor from an application standpoint. This work aims to highlight the influence of hydrothermal aging on the tribological and mechanical performance of polyamide 6 (PA6) and glass fiber-reinforced polyamide 6 (PA6-GF). The friction and abrasion wear behavior of unconditioned and conditioned PA6 and PA6-GF composites are measured against silicon carbide grinding paper on a pin-on-disk tribometer in a demineralized water medium at 60 °C. Specimens are conditioned in demineralized water at room temperature (RT) 25, 40, and 60 °C to investigate the effects of moisture and temperature. The presence of up to 25 wt.% glass fiber (GF) in PA6-based composites exhibits an increasing trend in abrasion wear mass loss and a reduction in coefficient of friction (COF). Interestingly, the mass loss of specimens conditioned to saturation does not increase compared to that of unconditioned samples. The FTIR spectroscopy is used to study the polymer degradation during hydrothermal aging.

Bioaugmented biological contact oxidation reactor for treating simulated textile dyeing wastewater

In this study, modified polyamide fibers were used as biocarriers to enrich dense biofilms in a multi-stage biological contact oxidation reactor (MBCOR) in which partitioned wastewater treatment zone (WTZ) and bioaugmentation zone (BAZ) were established to enhance the removal of methyl orange (MO) and its metabolites while minimizing sludge yields. WTZ exhibited high biomass loading capacity (5.75 ± 0.31 g/g filler), achieving MO removal rate ranging from 68 % to 86 % under different aeration condition within 8 h in which the most dominant genus Chlorobium played an important role. In the BAZ, Pseudoxanthomonas was the dominant genus while carbon starvation stimulated the enrichment of chemoheterotrophy and aerobic_chemoheterotrophy genes thereby enhanced the microbial utilization of cell-released substrates, MO as well as its metabolic intermediates. These results revealed the mechanism bioaugmentation on MBCOR in effectively eliminating both MO and its metabolites.

Waterless Dyeing of Polyamide 6.6.

Waterless dyeing of polyamide 6.6 using scCO2 (supercritical carbon dioxide) was investigated. PA (polyamide) fibers can be dyed with various dyes, including disperse dyes. The conventional aqueous dyeing process uses large amounts of water and produces polluted water. Considering these environmental issues, waterless dyeing of fibers is a forefront issue, and utilization of supercritical carbon dioxide (scCO2) is a commercially viable technology for waterless dyeing. This study tested PA6.6 (polyamide 6.6) dyeing in scCO2 at 100 °C 220 bar pressure for 45 min. Color measurements and color fastness tests were performed, as well as tensile strength, scanning electron microscope (SEM) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. PA6.6 fabrics yielded higher K/S (color strength, the Kubelka-Munk equation) values with larger molecular weight dye and almost the same color strength with medium and small-sized dyes, demonstrating the ability of dyeing in a supercritical environment without water as a more environmentally friendly dyeing option compared to conventional dyeing.

Performance and Life Cycle Assessment of Composites Reinforced with Natural Fibers and End-of-Life Textiles

The growing need for materials that are eco-friendly and sustainable in the industrial sector has shifted focus from synthetic fossil to natural fibers, alongside the utilization of recycled polymer textiles. This research introduces a novel method for using end-of-life textiles, such as polyester and polyamide fabrics, in the production of composite materials, aiming to lessen textile waste and enhance material longevity. The mechanical attributes of flax fabric (FF), flax–recycled polyamide fabric (F/RPA), and flax–recycled polyester fabric (F/RPES) composite laminates are assessed through tensile, flexural, interlaminar shear, and Charpy impact tests. The study revealed that the addition of end-of-life synthetic fibers improves tensile strength, while the trend in modulus values suggests that flax provides a high degree of stiffness to the composites, which is moderated by the addition of synthetic fibers. This effect is consistent across both tensile and flexural testing, although the impact on stiffness is more significant in bending. The inclusion of polyester fibers in the composite laminate resulted in significant enhancements, with an 11.1% increase in interlaminar shear maximum force, a 17.4% improvement in interlaminar shear strength, and a 67.1% rise in un-notch impact energy, compared to composites made with only flax fiber (FF). The microscopic examination uncovered the internal structure and demonstrated a clear, strong bond between the polyester and polyamide fiber layers with the flax fibers. Additionally, the life cycle assessment revealed that the F/RPES composite had less environmental impact than FF and F/RPA in all 18 categories analyzed. This indicates that the environmental footprint of producing F/RPES is smaller than that of both FF and F/RPA.

Preparation and characterization of composite-modified PA6 fiber for spectral heating and heat storage applications

Abstract Composite coating technology was used to prepare a modified polyamide 6 (PA6) polymer material masterbatch with low mutual interference and good spinnability using molybdenum oxide, tungsten trioxide, graphene oxide, etc., as modifiers. Experiment shows that using nanoscale composite-coated modified masterbatches capable of spectral heating and heat storage in the preparation of nylon 6 fiber, adding modified masterbatches with a mass ratio of 6% online, and controlling various process parameters can result in good functionality and usability as well as enable consistent production. Optimal production conditions are achieved by utilizing pre-dried PA6 chips with a moisture content of 420 ppm. The master batch is subjected to drying at a temperature of 95°C for 12 h. During this process, the master batch is introduced at an addition ratio of 6%. Subsequent spinning is conducted at a speed of 4,300 m·min−1 and a temperature of 255°C. Cooling is facilitated by air set at a temperature of 17°C, flowing at a speed of 0.45 m·min−1. In the production line, one roller operates without heating, while the second roller is maintained at a temperature range of 160°C. The stretching process is performed at a ratio of 1.3. To ensure proper lubrication, an oil rate of 1.3% is applied. These meticulously controlled process parameters collectively contribute to the most favorable production status.