Polyamide Fibers Research Articles

Enhancing the Wettability of Fibre Surface: A Comparative Experimental Study of Different Surface Activation Principles on Single Polyamide Fibre

In this study, we have compared three different principles of surface activation with regard to their effects on the properties of single polyamide fibres. The techniques used include the complexation-mediated surface treatment using CaCl2/EtOH/H2O solution (CEW), the atmospheric pressure plasma treatment with air (APPA) and grafting polymerisation process with 2- hydroxyethyl methacrylate (HEMA). The CEW modification, the plasma treatment and the grafting process induced a decrease in advancing contact angle and thus led to an improved wettability of the polyamide fibre. While for the CEW treatment, the decrease was solely due to a change in topography such as increased surface roughness leading to increased capillary effect, for the APPA and grafting technique the decrease was attributed to a combination of increased surface roughness and increased amount of oxygen or nitrogen-containing groups as detected by XPS. In addition, the fibre fineness decreased in the case of CEW treatment due to a dissolution of polyamide segments during the modification, while it increased in the grafting process due to an additional grafted layer. However, an increase in wetted length was observed for most samples, which was attributed to the increased waviness of the fibres. All treatments induced a decrease in fibre tensile strength that decreased with increasing treatment intensity.

Effect of fiber on tensile performance of fiber reinforced cementitious composites

This study evaluated the effect of fiber on pull-out and tensile properties by conducting pull-out tests and direct tensile tests on hooked steel fiber (HSF), bundle-type polyamide fibers (PA), and amorphous metallic fibers (AF) with various physical properties and shapes. As a result, the hooked steel fiber was pulled-out, and the bonding stress and mechanical bonding stress of the fiber and the matrix had a great influence on the tensile performance. PA and AF showed fracture behavior, and the tensile performance of the fiber itself had a great influence on the tensile properties.

Preparation of Bioactive Polyamide Fibres Modified with Acetanilide and Copper Sulphate.

This paper presents a simple method of obtaining polyamide 6 fibres modified with acetanilide and copper ions. During the spinning of the fibres with the additives applied, a partial reduction of CuSO4 to Cu2+ and Cu+ ions occurs, which is observed as a change in the blue colour of the prepared polyamide granulate to the grey-brown colour of the formed fibres. CuMPs obtained as a result of the salt reduction should give the obtained fibres bioactive properties. Three types of microorganisms were selected to assess the microbiological activity of the obtained fibres, i.e., Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli. The fibres have antibacterial activity against Gram-positive and Gram-negative bacteria. The largest inhibition zones were obtained for the Gram-positive bacteria Staphylococcus aureus, ranging from 1.5 to 4.5 mm, depending on the concentration of CuMPs. The morphology of the fibres' surfaces was examined by means of scanning electron microscopy (SEM) and optical microscopy (OM). The changes in the polymer structure chemistry are studied by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray structure studies (WAXS and SAXS) and an energy-dispersive spectroscopy (EDS) analysis. The newly obtained bioactive polyamide fibres can be used in many areas, including medicine, clothing and environmental protection for the production of filters.

Investigation of high temperature compaction on fracture toughness of 3D printed carbon fiber polyamide composites

Investigation of high temperature compaction on fracture toughness of 3D printed carbon fiber polyamide composites

Durably and intrinsically antibacterial polyamide 6 (PA6) via backbone end-capping with high temperature-resistant imidazolium

The antibacterial polyamide 6 (PA6) material has attracted great research interest due to its wide application in food packaging, biomedical fields, functional textiles, and other fields. However, it is still a challenge to prepare intrinsically antibacterial PA6 with highly efficient and durably antibacterial activity via polymerization. Herein, the antibacterial imidazolium ionic liquid of 3-carboxymethyl-1-decyl imidazole chloride was designed and synthesized for adapting the polymerization and processing temperature of PA6. Then antibacterial PA6 (PA6-IL) was synthesized through hydrolyzed ring-opening copolymerization with imidazolium at the end of the backbones. Compared to physical blending or post-modification methods, antibacterial agents as end-capping reagents of polymer backbones endowed PA6 with intrinsic antibacterial activity. As expected, the obtained PA6-IL exhibited not just comparable physicochemical and mechanical properties to conventional PA6 but excellent antibacterial activity of low antibacterial time to 60 min and durability for 28 days. Additionally, the corresponding electrospun PA6-IL nanofibrous membranes showed homogenous morphology and remarkable hydrophilicity of 7.7° as well as the high-efficient antibacterial activity. Melt-spun PA6-IL microfibers revealed a smooth surface as well as enhanced tensile strength and increased breaking elongation compared to those of conventional PA6. The PA6-IL microfibers also behaved with excellent antibacterial efficiency and durability. Accordingly, this work provides a feasible and straightforward strategy to prepare durably and intrinsically antibacterial PA6 materials especially PA6 fibers, which can be widely applied in the textiles field.

Construction of unsaturated systems on the surface of polyamide fibers

The design and development of functional superfine fiber substrates are a recent research hotspot in the industry. In this study, the materials of superfine polyamide fibers were used to hydrolyze under acidic conditions to produce amino and carboxyl groups on the surface of polyamide fibers. Then, methacrylic anhydride was used to react with the amino groups of the fibers, so that carbon–carbon double bonds were introduced to the surface of the polyamide fiber and the surface of the polyamide fiber with a carbon–carbon double bond was obtained. In this paper, the effects of methacrylic anhydride dosage, reaction time and reaction temperature on the carbon–carbon double bond content were systematically investigated and characterized by ATR-IR and nuclear magnetic resonance. The results show that the amount of methacrylic anhydride was 1.2 mL, the reaction temperature was 50°C, and the reaction time was 2 h. The polyamide methacrylamide fiber contained the most carbon–carbon double bonds, and the grafted double bond content of the modified polyamide fiber was 6.39% of its dry weight.

The TU Wien Turbulent Water Channel: Flow control loop and three-dimensional reconstruction of anisotropic particle dynamics.

A horizontal water channel facility was built to study particle dynamics in a turbulent flow. The channel is sufficiently long to produce fully developed turbulence at the test section, and the width-to-height ratio is sufficiently large to avoid the sidewall effect for a large proportion of the cross-section. The system was designed to study the dynamics of complex-shaped particles in wall-bounded turbulence, the characteristics of which can be finely controlled. A maximum bulk velocity of up to 0.8ms-1 can be achieved, corresponding to a bulk Reynolds number of up to 7 × 104 (shear Reynolds number ≈1580), and flow parameters can be controlled within ±0.1%. The transparent channel design and aluminum structures allow easy optical access, which enables multiple laser and camera arrangements. With the current optical setup, a measurement volume of up to 54 × 14 × 54 mm3 can be imaged and reconstructed with six cameras from the top, bottom, and sides of the channel. Finally, the in-house developed reconstruction and tracking procedure allows us to measure the full motion of complex objects (i.e., shape reconstruction, translational, and rotational motions), and in this instance, it is applied to the case of microscopic, non-isotropic polyamide fibers.

The Antifungal Fibers of Polyamide 12 Containing Silver and Metal Oxides.

The textile market is a vast industry that utilizes antimicrobial polymeric materials, including various types of fabrics, for medical and personal protection applications. Therefore, this study focused on examining four types of antimicrobial fillers, namely, metal oxides (zinc, titanium, copper) and nanosilver, as fillers in Polyamide 12 fibers. These fillers can be applied in the knitting or weaving processes to obtain woven polymeric fabrics for medical applications. The production of the fibers in this study involved a two-step approach: twin-screw extrusion and melt spinning. The resulting fibers were then characterized for their thermal properties (TGA, DSC), mechanical performance (tensile test, DMA), and antifungal activity. The findings of the study indicated that all of the fibers modified with fillers kill Candida albicans. However, the fibers containing a combination of metal oxides and silver showed significantly higher antifungal activity (reduction rate % R = 86) compared to the fibers with only a mixture of metal oxides (% R = 21). Furthermore, the inclusion of metal oxides and nanosilver in the Polyamide 12 matrix hindered the formation of the crystal phase and decreased slightly the thermal stability and mechanical properties, especially for the composites with nanosilver. It was attributed to their worse dispersion and the presence of agglomerates.

Mechanisms of damage and fracture of aramid fibers: Focus on the role of microfibril cooperativity in fracture toughness

AbstractPushing the limits of synthetic polymers in terms of stiffness and strength, aromatic polyamide fibers–like Kevlar®–are used for demanding applications in the form of fiber assemblies as ropes. The unique mechanical performance of aramid fiber is intimately linked to its hierarchical structure and orientation, induced during the spinning process. Surprisingly, after nearly 60 years of heavy use, very little is known about damage mechanisms and rational explanation of such high resistance. We report an experimental investigation of the fiber damage mechanisms at the single fiber scale (diameter ≅ 10 μm) with the aim to establish a link with the microstructure. Damage mechanisms and crack propagation are observed in situ for the first time and unveil a widespread damage over the entire length of the fiber in the form of a network of transverse and longitudinal cracks. These observations make it possible to draw a novel scenario of fracture that mitigates the small strain failure hypothesis. To shed light on the crucial role of microfibril cooperativity in fracture toughness, a slight twist is applied to the single fiber to promote tortuosity and frictional contacts between microfibrils. Statistical fracture analysis demonstrated the beneficial impact of such torsion on early failure events, since lowest fracture stresses are shifted to higher stresses.

Modified polyamide fibers with low surface friction coefficient to reduce microplastics emission during domestic laundry

The widespread presence of microplastics has become a serious threat to humans and ecological environments because they carry many pollutants and can be easily ingested by aquatic organisms. Fibrous microplastics (FMPs) released from synthetic fiber garments during domestic laundry are a major source of contamination. Herein, we report a facile FMPs mitigation strategy for polyamide 6 (PA6) fibers by incorporating environmentally friendly polydimethylsiloxane (PDMS) during melt spinning. The obtained PA6/PDMS fibers showed a lower friction coefficient than the pure PA6 fibers. Surface morphology, tribology, and washing characterizations verified that a 60% reduction in FMPs shedding was achieved by reducing the friction. In addition, the low-surface-friction PA6/PDMS fabrics with high hydrophobicity exhibited improved waterproof and anti-stain behaviors. It is important to note that none of the essential properties, such as surface structure, dyeing and printing of the fabrics were compromised after PDMS blending. This study provides a green and scalable route for mitigating laundry microfibers using a fiber domain design.

Mechanical and dry sliding wear performance evaluation of marble dust particulates–lapinus fiber–polyamide 66 polymer composites with ranking analysis using hybrid AHP-R method

This research investigates the physical, mechanical, thermal, thermomechanical and dry sliding wear performance of marble dust particulates (0–20 wt.% @ step of 5%) and lapinus fiber (10 wt.% constant) reinforced polyamide 66 polymer composites, resulting in five hybrid polymer composite namely PLM-0, PLM-5, PLM-10, PLM-15 and PLM-20, respectively. A twin screw extruder and injection molding machine were used for the fabrication. Taguchi's method and ANOVA tools are used to optimize and determine the significant order of the input parameters for the sliding wear process, followed by surface morphology investigations. Finally, the hybrid AHP-R ranking method was applied to rank the compositions on their merits. It is observed that PLM-10 hybrid polymer composites have shown relative overall optimized performance. It shows the lowest density of 1.21 g/cc, voids content of 6.47%, water absorption of 4.51% and a specific wear rate of 1.03 × 10−3 mm3/Nm. In comparison, it shows the highest tensile strength of 112.64 MPa, flexural strength of 150.40 MPa, Rockwell hardness of 60.40 HRM, fracture toughness of 4.27 MPa√m, impact strength of 1.96 J, thermal conductivity of 0.98 W/mK and storage modulus of 1824.29 MPa. Finally, these subjective findings were found to be in tune with the findings of the hybrid AHP-R method.

Mechanical Properties of Polyamide Fiber-Reinforced Lime–Cement Concrete

Lime–cement concrete (LCC) is a type of lime-based concrete in which lime and cement are utilized as the main binding agents. This type of concrete has been extensively used to construct support layers for shallow footings and road backfills in some warm regions. So far, there has been no systematic research conducted to investigate the mechanical characteristics of polyamide fiber-reinforced LCC. To address this gap, LCC specimens were prepared with 0%, 0.5%, 1%, and 2% of polyamide fibers (a synthetic textile made of petroleum-based plastic polymers). Specimens were then cured for 3, 7, and 28 days at room and oven temperatures. Then, the effects of the fibers’ contents, curing conditions, and curing periods on the mechanical characteristics of LCC, such as secant modulus, deformability index, bulk modulus, shear modulus, stiffness ratio, strain energy, failure strain, strength ratio, and failure patterns, was investigated. The results of the unconfined compressive strength (UCS) tests showed that specimens with 1% fiber had the highest UCS values. The curing condition and curing period had significant effects on the strength of the LCC specimens, and oven-cured specimens developed higher UCS values. The aforementioned mechanical properties of the LCC specimens and the ability of the material to absorb energy significantly improved when the curing period under the oven-curing condition was increased, as well as through the application of fibers in the mix design. Based on the test results, a simple mathematical model was also established to forecast the mechanical properties of fiber-reinforced LCC. It is concluded that the use of polyamide fibers in the mix design of LCC can both improve mechanical properties and perhaps address the environmental issues associated with waste polyamide fibers.

Enhanced Thermal and Mechanical Properties of Electrospun PA-6 Nanofibers by Embedding Alumina and Tungsten Carbide Particles

Electrospinning is a process in which solid fibers are prepared from polymer solution. In recent decades, studies have focused on improving the properties of electrospun nanofibers by exploring the possibilities of electrospinning different polymers. Two critical properties that have been studied in relation to this technique are thermal stability and mechanical properties. In this study, polyamide-6 (PA-6) nanofibers were prepared by embedding combinations of alumina and tungsten carbide particles. The morphology of the resulting hybrid nanofibers was analyzed using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC) and Thermogravimetric (TGA) techniques, and tensile tests were performed to evaluate their mechanical properties. The results showed that the sample containing tungsten carbide with a weight ratio of 4:10 had the highest melting standard enthalpy. The analysis also revealed that hybrid fibers containing equal ratios of alumina and tungsten carbide, each with a weight ratio of 2:10, had higher degradation temperatures and melting enthalpy compared to other nanofibers. Tensile testing showed that nanofibrous mats containing tungsten carbide had higher Young’s modulus, PA-6 fibers.

Production of electrospun hybrid membranes based on polyamide 6 reinforced with hemp fibers dissolved in 1-ethyl-3-methylimidazolium dicyanamide ionic liquid

This paper is focused on the fabrication of novel hybrid materials based on electrospun polyamide fibers reinforced with hemp fibers (HF) dissolved in 1-ethyl-3-methylimidazolium dicyanamide ionic liquid (IL). The physical properties of the hybrid electrospun materials have been evaluated. SEM micrographs showed an interconnected structure between polyamide 6 (PA6) and IL dissolved hemp fibers. X-ray and FTIR analysis were carried out to support the SEM images. DSC and TGA profiles gave information related to the thermal stability of electrospun membrane while barrier properties analysis proved the improvement in terms of water sensitivity and reduction of water clustering phenomena. Moreover, the improvement of mechanical properties was obtained after the introduction of IL dissolved HF leading to an increase in Young’s modulus of about 640 %. The antioxidant properties of reinforced PA6 fibers were even carried out, proving an enhancement of radical scavenging activity of about 68 %. Finally, the computational work and the estimation of surface energy distribution were reported.

Elastomeric coatings reinforced with fibers for metallic surfaces

Polymeric coatings are widely used on metallic pipes in the mining industry, mainly to prevent corrosion and wear. In this study, natural rubber composite reinforcements were prepared with two different proportions of synthetic, mineral and natural fibers and then evaluated. The composites were initially processed in a closed mixer, followed by homogenization in a cylinder. One of the natural fibers used was assessed with and without previous chemical treatment. The treatments were evaluated with thermogravimetry, Fourier transform infrared spectroscopy and scanning electron microscopy. The rheological, mechanical and wear data for all formulations were also addressed. The glass fiber, polyamide, basalt, and natural jute fiber samples showed reinforcing capabilities similar to that the standard sample (fiber-free composition). The formulations prepared with the chemically treated jute fiber, on the other hand, showed the best mechanical results, adhesion with the metal and abrasion wear resistance. In summary, these formulations prepared with natural raw materials could be alternatives for the composites used to coat industrial pipes.

Assessment of mechanical properties of fiber reinforced cementitious system exposed to high temperature

AbstractIn this study, it was aimed to determine the optimum fiber type and usage ratio by examining the effect of fiber type and usage rate on the properties of mortar mixtures exposed to high temperatures such as 300°C, 450°C, and 600°C. For this purpose, mixtures were prepared by substituting polypropylene (PP), polyamide (PA) and basalt (B) fibers in proportions as 0.25%, 0.50%, 0.75%, and 1% instead of aggregate. Unit weight, compressive‐flexural strength, ultrasonic pulse velocity (UPV), and permeability properties of mixtures were determined. Regardless of fiber type, flexural strength and permeability increased, UPV decreased with the addition of fiber. Basalt fiber mixtures exhibited the highest performance in terms of flexural strength. PP fiber mixtures exhibited the best performance in terms of permeability, ultrasonic pulse velocity and dynamic modulus of elasticity. SEM analyzes showed that PP fibers exposed to 600°C melted, leading to the formation of channel voids. According to TGA result, approximately 15% mass loss was observed in the control sample at 600°C.

Discussion on Factors Affecting Dyeing of Bio-based Polyamide 5,6 Fibers Compared with Polyamide 6,6 Fibers

To replace petroleum-based nylon and broaden the applications of polyamide 5,6 (PA56) in textiles, it is necessary to investigate the factors affecting the dyeing of bio-based PA56. In this work, bio-based PA56 and polyamide 6,6 (PA66) fibers were dyed with an acid dye. A comprehensive comparison of the factors affecting the dyeing performance of the PA56 and the PA66 fibers was carried out by measurements of the end-group content, crystallinity, and free volume fraction. The free volume fractions of the fibers in the dyeing process were calculated by the Williams-Landel-Ferry equation. Compared to the PA66 fibers, the results showed that the PA56 fibers had a better dyeing performance and water absorption behavior. Under the conventional dyeing process with water, the free volume fraction of PA56 fibers was slightly larger than that of the PA66 fibers. The larger the free volume, the more space for segmental motion and the easily entering of the dye into the interior of a fiber. The crystallinity of the PA56 fibers was 26.9%, which was lower than the 35.6% of the PA66 fibers. The lower crystallinity of the PA56 fibers means less regularity of macromolecular arrangement. The end-amino groups of the PA56 fibers and the PA66 fibers were 39.6 mmol/kg and 44.7 mmol/kg, respectively. Since the -NH2 groups only existed on the end of the polymer chains and the amount of -NH2 groups was low, the effect of the -NH2 groups content on the dyeing results was very small. Taking all these factors into consideration, the lower arrangement and the better segmental mobility of the molecular chains in the amorphous areas gave rise to the better dyeing performance of the PA56 fibers.

Mechanical Properties of Ternary Composite from Waste Leather Fibers and Waste Polyamide Fibers with Acrylonitrile-Butadiene Rubber.

This study aimed to improve the mechanical properties of a composite material consisting of waste leather fibers (LF) and nitrile rubber (NBR) by partially replacing LF with waste polyamide fibers (PA). A ternary recycled composite NBR/LF/PA was produced by a simple mixing method and vulcanized by compression molding. The mechanical properties and dynamic mechanical properties of the composite were investigated in detail. The results showed that the mechanical properties of NBR/LF/PA increased with an increase in the PA ratio. The highest tensile strength value of NBR/LF/PA was found to have increased about 1.26 times, that is from 12.9 MPa of LF50 to 16.3 MPa of LF25PA25. Additionally, the ternary composite demonstrated high hysteresis loss, which was confirmed by dynamic mechanical analysis (DMA). The presence of PA formed a non-woven network that significantly enhanced the abrasion resistance of the composite compared to NBR/LF. The failure mechanism was also analyzed through the observation of the failure surface using scanning electron microscopy (SEM). These findings suggest that the utilization of both waste fiber products together is a sustainable approach to reducing fibrous waste while improving the qualities of recycled rubber composites.

Measurement of the conductive fabric contact impedance for bioelectrical signal acquisition purposes

Information about the physiological state of the human organism can be obtained by detecting bioelectrical signals. The detection electrodes are a critical point in the measurement chain. The use of textile electrodes is advantageous due to comfort and less stressful measurement of bioelectrical signals for the patient. A unique automatized measurement system was proposed to measure contact impedance magnitude and phase. This research investigated several conductive textile materials in terms of impedance at the artificial electrode–skin interface to select the most appropriate material for ECG signal acquisition. The most suitable samples for further investigation appeared to be polyamide fibre covered with pure silver, without/with antioxidant treatment. These materials were further compared to conventional Ag/AgCl electrodes while measuring ECG on living subjects. Signal quality metrics show a high level of similarity between the ECG signals measured by textile electrodes and conventional Ag/AgCl electrodes.

Microplastics in aquatic species of Anzali wetland: An important freshwater biodiversity hotspot in Iran

Coastal wetlands are sensitive ecosystems that give habitat to large number of species. The extent of the impact of microplastic pollution in the aquatic system and humans is not known. In this study, the occurrence of microplastics (MPs) was assessed in 7 aquatic species from the Anzali Wetland (40 fish and 15 shrimp specimens), a listed wetland on the Montreux record. Specifically, the tissues analyzed were gastrointestinal (GI) tract, gills, skin, and muscles. The total frequency of MPs (all detected MPs in the GI tract, gill and skin samples) varied from 5.2 ± 4.2 MPs/specimen for Cobitis saniae to 20.8 ± 6.7 MPs/specimen for Abramis brama. Among all tissues studied, the GI tract of the Chelon saliens, a herbivorous demersal species, had the greatest level of MPs (13.6 ± 10 MPs/specimen). Significant differences (p < 0.05) were found between the abundance of MPs in different species, tissues, living domains and feeding habit types. The findings support that fish may uptake MPs through adherence in gills (respiration) in addition to ingestion. White/transparent and black/grey polyamide (PA) fibers were the most common type of MP which may be originated from municipal wastewater and intensive fishing activities. About 34% of the MPs were in the range of 250 μm–500 μm, and those >100 μm were not detected in muscles from the study fish. All species had unhealthy weight according to the Fulton's condition index (K). Positive relationships existed between biometric properties (total length and weight) of species and the total frequency of uptaken MPs, pointing to detrimental impact of MPs in the wetland.