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Recently, reverse osmosis (RO) has become the most widely used process in membrane technology. It has aroused great interest in water desalination through membranes. According to recent studies, the surface properties of support layers in thin film membranes are crucial for improving reverse osmosis performance. Surface polymerization was used to produce the membranes in this work, with the polyamide acting as a selective layer on the polysulfone support film. Three membranes were produced with different proportions of molybdenum sulfide (MoS2) nanopowder. The effectiveness of the membranes was improved by increasing water permeability while maintaining excellent salt retention. All membranes produced were tested using various characterization methods including scanning electron microscope, Brunauer-Emmett plate, and zeta potential. The water permeability of the polyamide membrane with PA-MoS2 (0.015% w/v) was 29.79 L/m2 h bar, more than the PA-MoS2 membranes (0.005% w/v, 19.36 L/m2 h) and PA-MoS2 (0.01% w/v, 3.63 L/m2 h bar). Under the same conditions, salt rejection of more than 96.0% for NaCl and 97.0% for MgSO4 was also observed. According to the SEM, the 0.015% PA-MoS2 membrane exhibited lower surface roughness, greater hydrophobicity, and a higher water contact angle. Due to the hydrophobic nature of MoS2, these properties resulted in the lowest salt rejection. [ABSTRACT FROM AUTHOR]

This study employed two prevalent plastic products - straws and microfiber as microplastics (MPs) to elucidate their largely unexplored effects on soil's properties and the growth of the tomato plant (Solanum lycopersicum L.). For this experiment, a completely randomized design (CRD) was adopted where, straw - polypropylene (PP), microfiber - polyester (PES) + polyamide (PA), and their combinations (PP + PES + PA) were mixed with soil using different concentrations – 0% (control), 0.4%, 1%, and 2% (treatments) and kept for 45 days at room temperature. The findings demonstrated that incorporating 2% mixed MPs in soil significantly decreased bulk density and electrical conductivity 7.29% and 67.3%, respectively, while soil pH increased 17.84% in cultures containing 1% microfiber. Maximum water holding capacity (MWHC), soil organic carbon (SOC), and soil organic matter (SOM) showed varied responses based on MPs type and concentration. Specifically, MWHC increased 16.4% with 2% microfiber but declined 13.3% with 0.4% straw. The highest decreased (30.65%) in SOC and SOM were evident in cultures with 1% microfiber whereas increased 9.68% and 8.33% in cultures with 0.4% straw. In terms of the growth traits of S. lycopersicum, substantial reductions in plant height (56.37%), leaf number (54.37%), and girth diameter (56.43%) were observed in 2% straw containing cultures. Although no plant mortality was noted, the most pronounced reductions in leaf area (62.44%) and total plant biomass (68.16%) occurred in 2% microfiber cultures. Therefore, the ramifications of these findings may contribute to a deeper comprehension of the mechanisms and effects of MPs on soil properties and above-ground plant growth. [ABSTRACT FROM AUTHOR]

In the present study, a drug-delivery system based on electrospun nanofiber was developed. Polyamide (PA) as a fibers matrix was employed for the delivery of the anticancer drug doxorubicin (DOX). The nanofiber (NFs) was initially modified by incorporating β-cyclodextrin (β-CD) to generate an inclusion complex of β-CD and drug. The modified nanofiber was subsequently fabricated via an electrospinning approach of DOX/β-CD-incorporated PA. For understanding the role of β-CD in the inclusion of DOX, a DOX-incorporated nanofiber (i.e., PA/β-CD) was fabricated for comparison. β-CD enhanced the loading of DOX into PA NFs, resulting in an increased loading efficiency of 56% (PA/β-CD/DOX), compared to 47% for PA/DOX. In addition, the release profile of DOX and the effect of β-CD on the release behavior were investigated. The results demonstrated a substantial release of the drug (total release = ~ 92%) from PA/β-CD/DOX NFs, with a slower release rate (within 4 days) compared to PA/DOX without β-CD (total release = ~ 77%). Consequently, β-CD played a significant role in the sustained release of the drug. The viability of prostate cancer and LNCap cells in response to the drug was assessed for the NFs. The decreased cell viability observed in PA/β-CD/DOX indicates a sustained and controlled release behavior for this drug carrier system. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) and concentrated brine are widely present in the coastal area due to accelerated human activities. However, the changes in the adsorption behavior of microplastics for different pollutants under high salinity conditions and their effects on the single/complex behavior of aquatic organisms are not yet clear.. In this work, polystyrene (PS) and polyamide (PA) microplastics were selected to study their effect on the adsorption behavior of three typical water pollutants (Pb2+, 4-chlorophenol, and levofloxacin) at high salinity. Furthermore, the individual and combined toxic effects of MPs and high salinity on Synechococcus were primarily explored. Activities of superoxide dismutase and catalase, concentrations of reduced glutathione and chlorophyll-a were employed as toxic indicators. Our results showed that salinity significantly changes the adsorption behavior of the three pollutants onto MPs and alters the toxic effect of MPs. Under the condition of 6% salinity and 10 mg/L MPs, PS-MPs did not significantly affect the cellular metabolism and photosynthetic efficiency of Synechococcus, while PA-MPs showed an evident synergistic effect with the high salinity. Copresence of high salinity with MPs reduced the individual toxic effect of PS-MPs and PA-MPs. This study shows that high salinity seawater can significantly alter the adsorption behavior of microplastics to other pollutants and their toxic effects on organisms. The impact of high-salinity brine on the marine ecology should be considered before construction of desalination projects. [ABSTRACT FROM AUTHOR]

The hydrophobicity of polyamide (PA) hinders the comfort and processing of fabrics. The enzyme-catalyzed surface modification has emerged as a promising alternative to conventional chemical methods for hydrophilic modification of PA due to the continuously increasing concern on environmental sustainability. However, the hydrolysis effect is weak. An effective method was developed to circumvent this limitation resulting in polyamide with good hydrophilicity and dyeing properties. The modification route included the swelling pretreatment based on ethanol, bromelain-catalyzed hydrolysis and laccase-catalyzed grafting. The swelling pretreatment greatly improved the accessibility of bromelain to PA. Thus, the hydrolysis effect was enhanced by 0.63% in a short time. Then, the Laccase/TEMPO system oxidized trehalose to complete the grafting on the surface of the PA fabric. The static water contact angle and dye uptake of EA@BM@LAC modified PA fabric increased by 59.8% and 17.4%, respectively. This work proposed a green and multi-enzyme system to achieve surface hydrophilic modification of PA and promoted the comprehensive utilization of enzymes in the textile field. [ABSTRACT FROM AUTHOR]

In recent years, metal nanoparticles (MNPs) have gained significant research interest owing to their versatile characteristics in diversified applications ranging from catalysis to biomedical sciences. Due to their notable and improved properties such as higher flexibility, facile processability, thermal stability, mechanical strength, and exceptional optoelectrical and magnetic behavior as compared to pristine metal nanoparticles, the polymer mediated nanoparticles have recently drawn interest from both industry and academia. In this novel investigation, we report a sustainable synthesis of Ag, Fe, Cu, and Zn metal nanoparticles using a chemical reduction method using polyamide (PA) and polyhydrazide (PH) matrices. This work is innovative in that it makes use of these polymer matrices for improved MNP synthesis, offering a unique combination of thermal and structural features. The polymers-supported metal nanoparticles were characterized for structural, thermal, optical, chemical, and morphological characteristics using XRD, TGA, UV-Vis, IR spectroscopy, and SEM analysis, respectively. XRD measurements demonstrated a significant rise in the crystallinity index for the produced metal nanoparticles, indicating a significant increase in crystallinity quantitatively. The effective synthesis of nanoparticles with precise attributes was confirmed by UV-Vis spectroscopy, which showed a significant absorption peak in the UV region. The thermogravimetric study suggested an improvement in thermal stability of around 25%. This work offers a flexible and eco-friendly method for synthesizing metal nanoparticles, demonstrating the usefulness of polyamide and polyhydrazide matrices as platforms for the synthesis of nanomaterials for numerous applications including catalysis, electronics, sensors, and biomedical applications. Highlights: A facile synthesis of metal nanoparticles (Ag, Fe, Cu, and Zn) via chemical reduction approach. The nanoparticles of Ag, Fe, Cu, and Zn are formed utilizing polyamide (PA) and polyhydrazide (PH) matrices. The synthesized metal nanoparticles exhibited higher crystallinity, better thermal stability, high absorption in UV range. This work offers a potential for numerous applications including catalysis, electronics, sensors, and biomedical applications. [ABSTRACT FROM AUTHOR]

The forward osmosis (FO) process has recently gained significant interest in treating wastewater, brackish/seawater and concentrating feedstocks for various operations, including desalination. The study investigates the effect of different synthesis conditions of the polyamide-based thin-film composite (TFC) FO membranes on the membranes' final performance. Taguchi statistical analyses were used to fabricate and optimize the polyamide TFC FO membrane. The process parameters as factors were the amount of polyethersulfone (PES), polyethylene glycol 400 (PEG-400), polyvinyl pyrrolidone (PVP), m-phenylenediamine (MPD), and trimesoyl chloride (TMC), and TMC reaction-time (RT). The Taguchi method was adopted to investigate the optimal conditions and the significance of individual factors using an L16 (45) orthogonal array. Another Taguchi analysis (Taguchi 2) was adopted to investigate the influence of other important parameters like optimal conditions for MPD, TMC, and TMC reaction-time factors using an L9 (33) orthogonal array. Confirmation tests validated a maximum water flux of 46.4 ± 2.32 L/m2·h with a specific combination of control factors for membrane synthesis: PES/PEG/PVP/MPD/TMC/TMC RT-16/7/0.5/1/0.05/30. These tests demonstrated a high-water flux of 7.05 ± 0.35 L/m2·h when exposed to industrial wastewater (secondary effluent) as the feed solution (FS) and fertilizer as the draw solution (DS) in the FO process. The R2 values were more than 90%. The experimental validation confirmed the models' predictive ability with different FSs, including industrial wastewater. [ABSTRACT FROM AUTHOR]

In recent years, it is seen that there have been many publications on natural dyes in literature. In the studies carried out, one or more plants were taken and the color and fastness obtained with them in the presence of different mordants were examined. Beyond that, functionalities such as odor, antibacterial activity, and UV protection that natural dyes impart to the fabric were examined. However, the important thing that the literature needs is to represent also the results related to the industrial scale production since industry shows high interest to be able to use natural dyes. In this study, seven plant dyes have been used for the coloration of polyamide fabric. The studies have been conducted both on an industrial scale and at the laboratory scale. Based on the statistical analyses, four dyes with the highest color strength and fastness properties including catechu, madder, mulberry leaf, and pomegranate peel were selected for more studies on industrial scale. The results confirmed the good color strength and satisfactory fastness properties against repeated washing, rubbing, water, and perspiration for all selected dyes. The samples dyed with those dyes exhibited excellent protection against UV radiation. The results obtained in this study showed the potential of the selected natural dyes in eco-friendly industrial dyeing of nylon fabric with acceptable fastness properties. [ABSTRACT FROM AUTHOR]

The objective of this experimental study is to utilize rotary friction welding (FW) for assembling similar polyamide materials. The application of the SVM approach enables the development of a predictive model for estimating mechanical properties in RFW processes. Furthermore, the optimization of RFW parameters through GA proves pivotal in selecting optimal welding conditions, providing a variety of choices. The welding parameters considered in this study included rotation speed at five levels and traverse speed at three levels. The strength of the welded samples was characterized by a tensile test. Additionally, temperature measurements were taken to determine the maximum temperature in the joint area. The results demonstrated the dependence of tensile strength and maximum temperature on the rotation speed. Maximum tensile strength is achieved at an optimal rotation speed. Moreover, analysis of variance (ANOVA) indicates that rotation speed is the parameter most influenced by tensile strength. [ABSTRACT FROM AUTHOR]

This study examined the kinetic reaction between hydrogenated dimer fatty acid C36 and 4,4′-methylene bis(cyclohexylamine) in the melt phase at 140, 145, 150, 160, and 165 ºC. The acid value, degree of polymerization, number average molecular weight, and weight average molecular weight were calculated at different times. Infrared spectroscopy was used to determine the structure of the resulting polymer. The kinetic degradation was carried out using thermogravimetric analysis, and thermodynamic and equilibrium constants were defined. Additionally, differential scanning calorimetric was used to determine the thermodynamic constants for melting. The kinetic of the polyamidation reaction was discovered to be of overall second order, with an activation energy of 187.45 kJ/g mol up to 80, 84, 92, 93, and 94% conversion at 140, 145, 150, 160, and 165 ºC, respectively. After reaching these conversion percentages, the reaction becomes overall third order. [ABSTRACT FROM AUTHOR]

With the rise of global demand for eco-friendly alternatives and the drive toward reducing the adverse environmental impact, the exploration of new sources of natural dyes has gained significant attention. This study focused on optimizing the dyeing process of polyamide fabric using Verbascum thapsus (Mullein) flower without mordant, as well as exploring the effectiveness of biomordants as sustainable alternatives to traditional metal mordants. To investigate the effectiveness of Verbascum thapsus flowers as a textile dye, the related color coordinates as well as color strength (K/S) of the fabric samples which had been dyed were measured. The color fastness of the samples which had been dyed using different mordants was also assessed. The optimized dyeing conditions for nylon 6 dyed with Mullein extract was achieved using pH = 3, temperature = 100 ℃, dye concentration = 100%, material-to-liquor ratio (M:L) = 1:30, and time = 60 min. Furthermore, the effectiveness of biomordants, including pistachio hull, pomegranate peel, oak gall, and Terminalia chebula, was compared with that of traditional metallic mordants (iron (II) sulfate, zinc sulfate, copper sulfate, and aluminum potassium sulfate) in terms of enhancing the dye absorption and colorfastness. The highest K/S value was obtained in dyeing after bio-mordanting with 50% pomegranate peel. In addition, the antibacterial activity was investigated and proved in this sample. The diameter of the inhibition zone of the nylon 6 fabric bio-mordanted with 50% owf pomegranate peel and dyed with 100% Verbascum thapsus was around 25 mm for P. aeruginosa and S. aureus. It was observed that biomordants, except for Pistachio hull, improved the associated color strength for the dyed nylon 6 fabric. In contrast, metallic mordants showed a decrease of color strength. Regarding color fastness, biomordants also had positive effects on color fastness. The results indicated that biomordants could be considered as environmentally friendly alternatives to metallic mordants in the related dyeing processes. These findings can be valuable in the development of eco-friendly dyeing processes for synthetic fibers. [ABSTRACT FROM AUTHOR]

Cold spray metallization of polymers is a promising surface engineering technique that enables the deposition of metal coatings onto polymer substrates at low process temperatures, resulting in improved surface properties, thus enhanced functionality of the polymeric material. However, deposition of well-adhering metallic coatings without causing surface damage to the polymer substrate is still a challenge. In this work, copper-polyamide composite coatings with different copper concentrations between 30 and 75 vol.% in the starting powders were deposited on polyamide substrates using a low-pressure cold spray system with two nozzle geometries of short and long diverging sections. The spray parameters were first developed for the deposition of polyamide powder (at gas temperature of 260 °C and gas pressures ranging from 0.41 to 1.37 MPa), and then used to spray the composite powder mixtures where the polyamide particles were acting as a binder for copper particles. Inflight and impact particle characteristics (velocity and temperature) of the polyamide powder were simulated to better understand the deposition properties. Considering that the selected conditions were suboptimal for the deposition of copper particles, no surface damage was caused as no penetration of the copper particles into the polymer substrate occurred. The results show that increasing the copper content in the powder mixtures significantly improved the resulting coating uniformity and the retained copper content. In addition, the coating deposited by spraying the powder mixture with a higher copper content of 75 vol.% and using the longer nozzle yielded the highest cohesion strength. To further improve coatings cohesion, two post-spray processing methods of furnace heating and hot pressing were used, and the effect of each process on coatings properties was investigated.Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Given name: [Kintak Raymond] Last name [Yu]. Also, kindly confirm the details in the metadata are correct.The author names are now correct: Kintak Raymond given name and Yu last name All other details are corrects [ABSTRACT FROM AUTHOR]

The effect of moisture on the photo-oxidative degradation of polyamide-6 (PA-6) was studied by analyzing the mechanical response after two different accelerated aging procedures. In the first aging procedure, the PA-6 was only exposed to ultra-violet (UV) radiation at 60 ∘ C. In the second procedure, the same duration of UV radiation was periodically interrupted while the relative humidity was raised to 100%. Diffusion-limited and nominally homogeneous degradation conditions were investigated using bulk and film specimens, respectively. Accelerated UV aging reduced the ductility of PA-6, but the additional hygrothermal exposure had no effect on the ductility or strength, indicating that humidity did not influence the photo-oxidation of PA-6. This finding contrasts with previous studies that found thermo-oxidation of PA-6 was accelerated by moisture. [ABSTRACT FROM AUTHOR]

The article presents the results of an experimental determination of the friction coefficient of various materials (95Kh18 steel and BrAZh9-4 bronze, F-4 fluoroplastic, PA-6 polyamide, and MPG-7 graphite) in a friction pair with single-crystalline aluminum oxide under low speeds and various loading conditions. Determining the friction coefficient of aluminum oxide at low sliding velocity allows recording and evaluating the static friction for various counterbody materials, identifying the mechanisms of interaction between rubbing bodies and their influence on friction processes. Studies of the tribological characteristics of single-crystal aluminum oxide show that it has no antifriction properties, and, when using it in a friction unit, we need to take into account the pairing material, the load on the friction contact, and the sliding velocity. Aluminum oxide has a high affinity for metals, which causes strong adhesive interaction up to wear with cohesive destruction of metals. Polymer materials such as fluoroplastic and polyamide weakly adhesively interact with aluminum oxide, which ensures stable sliding within lubrication with low friction coefficients over a wide range of loads and velocity. Dry friction of the self-lubricating graphite material is determined by the tribological properties of the graphite. At low loads and sliding velocity, the adsorption component of friction is revealed. When forces are sufficient to destroy bonds in crystalline layers of graphite, the friction process is limited by the effect of self-lubricating of graphite. [ABSTRACT FROM AUTHOR]

Thymoquinone (TQ) is a phytochemical compound present in Nigella sativa and has potential benefits for treating dermatological conditions such as psoriasis. However, its clinical use is limited due to its restricted bioavailability, caused mainly by its low solubility and permeability. To overcome this, a new transdermal drug delivery system is required. Nanoparticles are known to enhance material solubility and permeability, and hence, this study aimed to synthesize TQ-loaded L-arginine-based polyamide (TQ/Arg PA) nanocapsules incorporated into transdermal patches for prolonged delivery of TQ. To achieve this, Eudragit E polymer, plasticizers, and aloe vera as penetration enhancer were used to develop the transdermal patch. Furthermore, novel TQ/Arg-PA was synthesized via interfacial polymerization, and the resultant nanocapsules (NCs) were incorporated into the matrix transdermal patch. The Arg-PA NCs' structure was confirmed via NMR and FTIR, and optimal TQ/Arg-PA NCs containing formulation showed high entrapment efficiency of TQ (99.60%). Molecular and thermal profiling of TQ/Arg-PA and the transdermal patch revealed the effective development of spherical NCs with an average particle size of 129.23 ± 18.22 nm. Using Franz diffusion cells and synthetic membrane (STRAT M®), the in vitro permeation profile of the prepared patches demonstrated an extended release of TQ over 24 h, with enhanced permeation by 42.64% when aloe vera was employed. In conclusion, the produced formulation has a potential substitute for corticosteroids and other drugs commonly used to treat psoriasis due to its effectiveness, safety, and lack of the side effects typically associated with other drugs. [ABSTRACT FROM AUTHOR]

This study investigates a novel method of recycling end-of-life reverse osmosis (RO) membranes to enhance the mechanical properties of concrete. Reverse osmosis (RO) is a widely used technology for water purification and desalination, but it has various environmental problems that require attention. RO membranes have a short service life, resulting in the generation of end-of-life (E-o-L) RO membrane trash in thousands of tons each year, which is typically disposed of in landfills, polluting land resources. The RO membrane primarily comprises a thin-film composite of polyamide (TFC PA) as a filter medium. The material properties of TFC PA are studied and added to the concrete as an additive in the cement volume at 1 to 20%. The optimum mix is identified at 3.4% of TFC PA, and the mechanical properties are nearly 17% greater than the control mix. SEM/EDX shows a higher bonding between TFC PA and the concrete, and TGA results exhibit the mass loss increasing with the increase in TFC PA. MIP analysis shows that the volume of cumulative pores and intruded volume is increased with increasing TFC PA. A sustainability study was carried out to evaluate the energy consumed and embodied CO2 in the mixes and compared them with the control mix. The mathematical model for compressive strength at 7 days, 14 days, and 28 days is done using response surface methodology (RSM) with the independent variables of TFC PA, slump, and superplasticizer. The adopted regression illustrates a significant relationship between the response and variables, proving a higher R2 for all the models and optimal p-values for the responses. They show that TFC PA influences the enhancement of properties of concrete. The residual also proves to be very minimal in the model. [ABSTRACT FROM AUTHOR]

Mechanical recycling is an important alternative to reduce the amount of fossil resources needed to produce plastic materials. This research evaluated the theoretical recyclability of two multilayer films for meat products packages, composed of PE/PE/ad/PA/ad/PE/PE (Film A) and PE/ad/PA/EVOH/PA/ad/PE (Film B), using the RecyClass tool. Then, an extrusion was carried out as a post-industrial recycling step. Recycled films were prepared without compatibilizer and with different concentrations (5–7%) of a commercial compatibilizer based on maleic anhydride (MA), and were evaluated according to their chemical, thermal, morphological, and mechanical properties. Films without compatibilizer were classified as non-recyclable using RecyClass. However, the use of a compatibilizer proved to be promising for the recycling of these packages. The infrared spectra showed that the PA-MA-PE copolymer was obtained during the mixing, confirmed by the microscopy images, where the compatibilizer provided an adhesion between the mixing interfaces. The melting temperature of PE proved to be stable during processing. However, the compatibilizer addition resulted in changes in the PA melting temperature in Film A. Films with compatibilizer showed a significant increase in elongation at break compared to films without it. These results confirm the strong efficiency of PA-MA-PE compatibilization, which is an alternative for recycling multilayer packaging of meat products. [ABSTRACT FROM AUTHOR]

Purpose: A number of studies have been conducted on the occurrence, transport, and fate of microplastics in soil environments. The complexity of matrices presents significant challenges in investigating microplastics in soil, highlighting the need for further research and development in this field. In this review, sampling and pretreatment methods available for detecting and further studying microplastics in soil environments are primarily focused with a minor discussion on their various sources and behavior. Finally, based on the current research findings, the directions of future research are proposed as well. Methods: Based on a comprehensive search of the available database, we provide updated information on the sources and behavior of microplastics in the soil and the analytical techniques available for their study. Results: Previous studies have predominantly focused on microplastic contamination and its levels in various environments. We propose that the focus of microplastic research needs to be redirected to allow a better understanding of the behavior and impact of soil microplastics. The novel approach involves modeling the behavior of microplastics in the soil and associated environmental impacts and risks and developing standardized testing methods. These tools will provide a comprehensive strategy for creating a healthy and safe environment. Conclusions: As plastic production increases worldwide, the accumulation of microplastics in the soil also increases, with potentially adverse implications for food security, human health, and climate change. A comprehensive strategy for rational delineation of microplastic behavior in the soil, as presented here, is needed to counteract and control the environmental impact of microplastics. [ABSTRACT FROM AUTHOR]

The effect of glass fiber-reinforcement polymer Polyamide 66 on the uniaxial compressive mechanical response was measured over a wide strain-rate range from quasi-static tests with strain rate of 5×10–3 s–1 to impact tests with strain rate of 2×103 s–1. Dynamic compressive load was applied using a split Hopkinson pressure bar, whereas an electromechanical testing machine was used to carry out quasi-static experiments in displacement control to determine strain-rate sensitivity. The results demonstrate that strain rate significantly influences yield stress, post-yield behavior, and ductility of the two polymers under study. The yield stress experimental data are consistent with thermally activated processes. [ABSTRACT FROM AUTHOR]

This work studies the tensile behavior of polyamide 6 (PA6) at different strain rates using both experimental and numerical methods. Quasi-static and dynamic tensile tests are performed using a universal testing machine and a split Hopkinson tensile bar (SHTB). The stress-strain curves and specimen morphologies are obtained over a wide range of strain rates from 2.6 × 10–4 s–1 to 900 s–1. The tensile behavior of PA6 is sensitive to strain rate, and the yield strength and yield strain both increase with an increase of strain rate. The plastic stage of PA6 exhibits strain hardening characteristics under quasi-static loading, but strain softening characteristics under dynamic loading. The strain softening characteristics become more significant with an increase of strain rate. The quasi-static tensile mechanical responses of PA6 are analyzed by a ZWT viscoelastic constitutive model, while the dynamic ones are analyzed by a ZWT model with a damage factor. The experimental stress-strain curves are well described by the constitutive model. Three-dimensional incremental expressions of the constitutive model are given, and a user-defined constitutive subroutine is written. Numerical simulations on the stress wave propagation process and the stress-strain curves of PA6 under SHTB loading are conducted, with results that are consistent with the experiments. [ABSTRACT FROM AUTHOR]

Epoxy-polyamide CNTs reinforced nanocomposites have the excessive ability for their uniform structures and specific properties and have considerable attention owing to their potential applications. In this work, epoxy/polyamide (ER-PA) and CNTs reinforced epoxy/polyamide (ER-PA/CNTs) nanocomposites were prepared by using the solution casting method. Herein, Fourier transforms infrared spectroscopy (FT-IR) was applied to indicate the responsible functional groups, presented in the prepared nanocomposites. Surface morphology and particle dispersion of the prepared nanocomposites were examined by scanning electron microscopy (SEM). The obtained results demonstrated that the CNT's weight content, dispersion rates, and the surface functionalization of CNTs nanoparticles have a strong influence on the surface morphology of the prepared nanocomposites. The thermal properties and crystalline nature of the ER-PA/CNTs nanocomposites were studied by using thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analyses. The prepared nanocomposites showed good thermal stability and crystalline behavior as compared to the ER-PA nanocomposites network system. From the obtained results, it can be assumed that this effort can help to design other reinforced nanocomposites for promising applications in the nanocomposites materials industry. [ABSTRACT FROM AUTHOR]

This study addresses the significant concern of pharmaceutical contaminants, including antipyretic and antibiotic drugs, in municipal and industrial wastewater, impacting both the environment and human health. We investigate incorporating zinc-based metal-organic framework (Zn-MOF) nanofillers into polyamide layers, developing thin-film composite (PA-TFC) nanofiltration membranes via interfacial polymerization to remove paracetamol, ibuprofen, and amoxicillin from simulated wastewater. Characterization confirms Zn-MOF's presence in the PA-TFC membrane, affecting structural topology, pore size, contact angles, and zeta potential. Zn-MOF nanofillers strongly adhere to the polyamide layer, influencing membrane surface chemistry and morphology. The newly developed MOF/PA-TFC nanofiltration membranes demonstrate a remarkable water flux of up to 35 LMH, showcasing superior removal efficiency for the three pharmaceutical contaminants when compared to PA-TFC membranes. Specifically, the rejection rates for paracetamol, ibuprofen, and amoxicillin are notably high at 93%, 98%, and 99%, respectively. Consequently, this study establishes MOF/PA-TFC nanofiltration membranes as a highly efficient solution for removing emerging pharmaceutical contaminants from environmental water, promoting sustainability and safeguarding water resources. [ABSTRACT FROM AUTHOR]

Polyimine represents a rapidly emerging class of readily accessible and affordable covalent adaptable networks (CANs) that have been extensively studied in the past few years. While being highly malleable and recyclable, the pioneering polyimine materials are relatively soft and not suitable for certain applications that require high mechanical performance. Recent studies have demonstrated the possibility of significantly improving polyimine properties by varying its monomer building blocks, but such component variations are usually not straightforward and can be potentially challenging and costly. Herein, we report an in situ oxidation polymerization strategy for preparation of mechanically strong poly(imine-amide) (PIA) hybrid CANs from simple amine and aldehyde monomers. By converting a portion of reversible imine bonds into high-strength amide linkages in situ, the obtained hybrid materials exhibit gradually improved Young's modulus and ultimate tensile strength as the oxidation level increased. Meanwhile, the PIAs remain reprocessable and can be depolymerized into small molecules and oligomers similar as polyimine. This work demonstrates the great potential of the in situ transformation strategy as a new approach for development of various mechanically tunable CANs from the same starting building blocks. [ABSTRACT FROM AUTHOR]

In recent years, water purification by membrane desalination techniques has been growing drastically; after all, water scarcity is a significant issue to deal with in some parts of the world. To put one step forward toward resolving the issue of water scarcity, the best way is to upgrade the current desalination technique and membranes so that the output of clear water will be improved. In this review, we will focus on enhancing some crucial properties of the Polyamide (PA) and Polyimide (PI) membranes by incorporating some functional additives. Ag NPs (Silver nanoparticles), Cu NPs (Copper nanoparticles), GO (Graphene oxide), SWCNT (Single-walled carbon nanotube), and MWCNT (multi-walled carbon nanotube) are some of the additives which can be used with PA/PI active layer to improve some essential properties of membrane-like antifouling, biofouling, low water flux, selectivity, permeability, hydrophilicity, hydrophobicity, etc. The deposition of such additives onto the surface of the Polyimide/Polyamide coat or membrane can be done using interfacial polymerization or phase inversion. Membrane filtration can be done using reverse osmosis and electrodialysis techniques. A thin-film composite membrane comprising PA and MWCNTs, yielded a water flux of almost 25.9 L m−2 h−1, with a salt rejection of 98.1% exhibiting excellent hydrophilicity with a water contact angle of 59.6°. [ABSTRACT FROM AUTHOR]

This research aimed to explore the effect of different concentrations (5–7%) of PCA-MA (polyolefin compatibilizer additive with maleic anhydride) on the properties and migration potential of two different multilayer packaging materials currently used for meat products: PE/PE/ad/PA/ad/PE/PE and PE/ad/PA/EVOH/PA/ad/PE (PE: polyethylene; ad: adhesive; PA: polyamide; EVOH: ethylene vinyl alcohol). The incorporation of PCA-MA resulted in the reduction of the crystallinity index and consequently, a reduction in tensile strength and puncture resistance was experienced. Additionally, a loss of water vapor barrier was observed, and the overall and specific migrations of maleic anhydride to the aqueous and fatty food simulants were below the quantification limit of the methods used. Therefore, they are within the specifications of the current legislation of food contact materials. Overall, although PCA-MA incorporation resulted in some loss of packaging properties, this additive can be considered an attractive alternative to facilitate the recycling process of these complex materials. [ABSTRACT FROM AUTHOR]

In this study, the influences of styrene–butadiene–styrene block copolymer (SBS), a thermoplastic elastomer, nanoclay (NC) and maleic anhydride grafted styrene–ethylene/butylene–styrene (m-SEBS), a compatibilizer, on the non-isothermal crystallization kinetics of polyamide 12 (PA12) have been evaluated using different theoretical models including Avrami, Jeziorny, Ozawa and Mo as well as Kissinger, Takhor and Augis and Bennett equations. Using microscopic observations, X-ray diffraction patterns and rheological responses, the interrelations among the crystallization kinetics variables, morphology and molecular dynamics of compatibilized PA12/SBS rubber/NC mixtures have been thoroughly investigated. A study on different kinetics variables such as crystallization half-time, Avrami index and F(T) demonstrates that the PA crystallization rate has an upward trend against the compatibilizer level within the studied compatibilizer content, while the rate shows a maximum value against NC loading and SBS content. The calculation of the rubber particles diameter, the distance between the rubber particles, PA/SBS interfacial area and normalized chain relaxation time clarifies that more heterogeneous nucleation sites are provided for PA chains by NC platelets and SBS particle surfaces at higher contents (higher amounts in the ranges of 15–21 mass% for SBS and 3–7 mass% for NC), though the molecular movements are restricted more as well, which reduces the growth rate of PA crystals. [ABSTRACT FROM AUTHOR]

Biobased polymers derived from plant oils are sustainable alternatives to petro based polymers. In recent years, multienzyme cascades have been developed for the synthesis of biobased ω-aminocarboxylic acids, which serve as building blocks for polyamides. In this work, we have developed a novel enzyme cascade for the synthesis of 12-aminododeceneoic acid, a precursor for nylon-12, starting from linoleic acid. Seven bacterial ω-transaminases (ω-TAs) were cloned, expressed in Escherichia coli and successfully purified by affinity chromatography. Activity towards the oxylipin pathway intermediates hexanal and 12-oxododecenoic acid in their 9(Z) and 10(E) isoforms was demonstrated for all seven transaminases in a coupled photometric enzyme assay. The highest specific activities were obtained with ω-TA from Aquitalea denitrificans (TRAD), with 0.62 U mg−1 for 12-oxo-9(Z)-dodecenoic acid, 0.52 U mg−1 for 12-oxo-10(E)-dodecenoic acid and 1.17 U mg−1 for hexanal. A one-pot enzyme cascade was established with TRAD and papaya hydroperoxide lyase (HPLCP-N), reaching conversions of 59% according to LC-ELSD quantification. Starting from linoleic acid, up to 12% conversion to 12-aminododecenoic acid was achieved with a 3-enzyme cascade comprising soybean lipoxygenase (LOX-1), HPLCP-N and TRAD. Higher product concentrations were achieved by the consecutive addition of enzymes compared to simultaneous addition at the beginning. Key points: • Seven ω-transaminases converted 12-oxododecenoic acid into its corresponding amine. • A three-enzyme cascade with lipoxygenase, hydroperoxide lyase, and ω-transaminase was established for the first time. • A one-pot transformation of linoleic acid to 12-aminododecenoic acid, a precursor of nylon-12 was achieved. [ABSTRACT FROM AUTHOR]

The present study investigates the natural dyeing of nylon fabric using the dragon's blood resin extract. Response surface methodology was used to optimize the process variables including pH (3–9), temperature (50–100 °C), concentration (10–50%owf), and time (30–90 min). From a visual point of view, diverse eco-friendly shades with a rather diverse color gamut of varied hue and tone were generated by applying a wide range of natural and eco-label mordants. The impact of 4 bio-mordants (including peppermint, mugworts (Artemisia), Dorema ammoniacum (DA) gum, and pomegranate rind), as well as 4 mineral mordants (alum, copper (II) sulfate, potassium dichromate, and iron (II) sulfate) on the color and fastness properties of the dyed nylon samples, was assessed. The concentration of the used mordants was 5%owf, and the dyeing experiments were conducted by applying the pre-mordanting technique. Measurement of the color strength (K/S) of the dyed fabric was done using a reflectance spectrophotometer. The dyed nylon fastness qualities and the colorimetric characteristics were then evaluated by applying the related standards. The results showed that the optimum conditions for obtaining the highest color strength were dye concentration = 50%owf, pH = 6, temperature = 100 °C, and dyeing tome = 60 min. The proposed ISO standards in relation to colorfastness displayed acceptable ratings for the color strength of dragon's blood resin dyed fabric while its treatment was done by applying bio-mordants in comparison to its metallic counterparts. Therefore, dragon's blood resin could be regarded as a promising eco-friendly natural colorant source for the purpose of sustainable nylon dyeing. [ABSTRACT FROM AUTHOR]

In this study, the low velocity impact behavior of glass fiber reinforced epoxy (GFRE) composites with the addition of organic intercalated nanoclay and spheroidal powder of polyamide nanoparticles individually and together were investigated experimentally. The weight ratio of the additives was 2% of the epoxy resin-hardener system. Composite laminates were manufactured using prepreg and hot-pressing techniques. Impact tests were carried out at different energy levels from 10 J to 45 J up to complete perforation of the laminates. To evaluate the damage characteristics of the laminates, the results are interpreted in terms of load-time, load-displacement, energy-time, and observation of the physical damages introduced. Addition of nanoparticles increased the peak load (up to 22.6%) and damage resistance (up to 40%) of the GFRE laminates altering damage mechanisms of the composite material from out of plane to in-plane direction at higher impact energy levels. [ABSTRACT FROM AUTHOR]

Metal-polyamide gear pairs provide advantages but their application is limited due to wear. The properties of the metallic gearing significantly affect the wear behavior. However, the influence of varying metallic materials as well as flank hardness is not known. Within this contribution, the occurring wear mechanisms when applying steel, brass and aluminum with varying hardness resulting from manufacturing by machining and cold forging were identified. Depending on the hardness of the metallic tooth flank, the release of metallic particles (3-body abrasion) or surface roughening (2-body abrasion) results. The formation of a wear-reducing transfer film is only possible with sufficient strength of the metallic tooth flank and tribological compatibility. Maximum wear occurs at a metal hardness of about 120 HV due to 3-body abrasion with high abrasive effect of the metallic particles. The adaptation of the cold forging process enables a local increase in the plastic strain of the tooth flank by 84% resulting in an elevated tooth flank hardness (+ 53%) for aluminum and significantly reduced wear. Furthermore, the formation of a wear-reducing transfer film results. Aluminum pinions produced in the adapted cold forging process achieve performance level of steel within the investigated load case. [ABSTRACT FROM AUTHOR]

Conventional fluorescent polymers are featured by large conjugation structures. In contrast, a new class of fluorescent polymers without any conjugations is gaining great interest in immerging applications. Polyamide is a typical member of the conjugation-free fluorescent polymers. However, studies on their electrophotonic property are hardly available, although widely used in many fields. Herein, poly(ethylene succinamide), PA24, is synthesized; its chemical structure confirmed through multiple techniques (NMR, FTIR, XRD, etc.). PA24 is highly emissive as solid and in its solution at room temperature, and the emission is excitation and concentration dependant, with an unusual blue shift under excitation from 270 nm to 320 nm, a hardly observed phenomenon for all fluorescent polymers. Quite similar emission behavior is also observed under cryogenic condition at 77 K. Its emission behavior is thoroughly studied; the ephemeral emission blue-shift is interpreted through Förster resonance energy transfer. Based on its structures, the emission mechanism is ascribed to cluster-triggered emission, elucidated from multi-analyses (NMR, FTIR, UV absorbance and DLS). In presence of a dozen of competitive metal ions, PA24 emission at 450 nm is selectively quenched by Fe3+. PA24 is used as probe for Fe3+ and H2O2 detections and in data encryption. Therefore, this work provides a novel face of polyamide with great potential applications as sensors in different fields. [ABSTRACT FROM AUTHOR]

Given the environmental burden of textile industry, especially of dyeing processes and the volume of synthetic dyes and surfactants, the intensive development of the greener approaches is under way. Herein, an environmentaly-friendly dyeing of polyamide (PA) and PA/Elastane (PA/EA) knits using live bacterial approach in water environment, completely eliminating usage of textile auxiliaries is described. A total of 12 pigment-producing Streptomyces strains were isolated and purified from soil and rizoshere or bark of smoke tree Cotinus coggygria samples. The antibacterial, antifungal and cytotoxic effects of crude bacterial extracts were tested. Antimicrobial effect was obtained by the majority of extracts but only two streptomycetes extracts, 11–5 and BPS51, showed moderate cytotoxicity against HaCaT human cell line. This was the reason to select 11–5 and BPS51 strains for the dyeing of the textile materials. Excellent properties of dyeing wool, silk and PA are achieved initially using live cultures, and the bioprocess is optimized on commercial PA and PA/EA knits used for stockings production. Satisfactory coloration of both knits is achieved with dynamic conditions (culture shaking at 180 rpm over 5–14 days at 30 ºC) giving the best coloration results, except in the case of the PA sample dyed with a bacterial strain 11–5. The prolongation of dyeing time leads to higher color yields independently of fabric and bacteria strain. Although the color differences between the samples before and after washing are observed, washing fastness after three washing cycles can be considered as satisfactory. [ABSTRACT FROM AUTHOR]

This study focuses on advancing epoxy-polyamide composites through the incorporation of chitosan, derived from crab shells, a sustainable polymeric bio filler known for its ability to enhance mechanical and thermal properties. Utilizing a solution casting technique, composites were fabricated by blending various concentrations of chitosan into the epoxy-polyamide matrix. Several analytical methods, including FT-IR, XRD, SEM, DSC, and mechanical testing, were used to evaluate the modifications and properties of the composites. FT-IR confirmed successful chitosan incorporation into the ER-PA composites, supported by SEM analysis showing improved structural integrity. XRD revealed prominent diffraction peaks, reflecting increased crystallinity and efficient chitosan integration. SEM indicated uniform chitosan dispersion on smooth surfaces, enhancing fracture toughness. Mechanical study of the 1% chitosan blend demonstrated superior results, with an elasticity of 6.79 GPa and fracture elongation of 2.2%, surpassing the 5% blend. DSC data showed improved thermal stability, with the uncured composite exhibiting endothermic behavior at 100 °C and exothermic behavior at 400 °C. TGA confirmed enhanced thermal properties up to 780 °C, particularly for the 1% Cs blend, which also displayed outstanding amorphous characteristics. Overall, the mechanical study confirmed Young’s best modulus, toughness, and tensile strength in the 1% blend. A noticeable shift toward higher temperatures during accelerated heating indicated enhanced material durability. These findings highlight the significant potential of chitosan to improve the mechanical strength and thermal stability of epoxy-polyamide composites, making them suitable for demanding engineering applications where endurance and performance are critical.Graphical abstract: This study focuses on advancing epoxy-polyamide composites through the incorporation of chitosan, derived from crab shells, a sustainable polymeric bio filler known for its ability to enhance mechanical and thermal properties. Utilizing a solution casting technique, composites were fabricated by blending various concentrations of chitosan into the epoxy-polyamide matrix. Several analytical methods, including FT-IR, XRD, SEM, DSC, and mechanical testing, were used to evaluate the modifications and properties of the composites. FT-IR confirmed successful chitosan incorporation into the ER-PA composites, supported by SEM analysis showing improved structural integrity. XRD revealed prominent diffraction peaks, reflecting increased crystallinity and efficient chitosan integration. SEM indicated uniform chitosan dispersion on smooth surfaces, enhancing fracture toughness. Mechanical study of the 1% chitosan blend demonstrated superior results, with an elasticity of 6.79 GPa and fracture elongation of 2.2%, surpassing the 5% blend. DSC data showed improved thermal stability, with the uncured composite exhibiting endothermic behavior at 100 °C and exothermic behavior at 400 °C. TGA confirmed enhanced thermal properties up to 780 °C, particularly for the 1% Cs blend, which also displayed outstanding amorphous characteristics. Overall, the mechanical study confirmed Young’s best modulus, toughness, and tensile strength in the 1% blend. A noticeable shift toward higher temperatures during accelerated heating indicated enhanced material durability. These findings highlight the significant potential of chitosan to improve the mechanical strength and thermal stability of epoxy-polyamide composites, making them suitable for demanding engineering applications where endurance and performance are critical. [ABSTRACT FROM AUTHOR]

Nanocalorimetry and Fourier transform infrared (FTIR) spectroscopy are combined to measure the calorimetric properties and molecular spectra of the same sample (sample amount about 5 ng) of polyamide 66 (PA66). By determining IR difference absorption spectra between a quenched and a sample annealed at varying temperatures (Ta) and annealing time (ta), the initial steps of homogeneous nucleation is for the first time revealed on a molecular scale, long before crystallization takes place. As starting point (i), isolated H-bonds are formed between (N–H) and (C = O) moieties of adjacent (neighboring) polymer segments promoted by far-reaching dipole–dipole interactions. In the second step (ii), the H-bonds realign, which in part requires the opening of already established H-bonds. In stage (i), the FTIR absorption intensity of the free (C = O)f moieties decreases while that of the H-bonded (C = O)b ones increases as a function of Ta at constant ta. This implies an increase in the H-bonding network in amorphous domains. The second stage of nucleation in the studied PA66 is characterized by an increase in the number of (C = O)f and a corresponding decrease in (C = O)b moieties as the sample transitions to the ordered crystalline structure. This is attributed to a change from γ to α polymorphs in PA66. The non-polar methylene units in PA66 are largely unaffected during the nucleation steps, where no changes in the overall heat capacity are detectable, proving that these changes occur prior to the onset of crystal growth. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on Polyamide 6.6 (PA6.6) monofilaments for needle-punching tests. First, a device especially developed for this study is described and the experimental protocol is presented. Based on these experiments, a numerical finite element model was set up to take into account the influence of the strain location on the breaking strength of PA6.6 filaments. The variability of the rupture force values was also presented in this model through a statistical breakage criterion using the Weibull formalism. A satisfactory correlation between experiments and simulations results was obtained with respect to the values of force at rupture. Thus, the model presented in this paper was able to take into account the variability of the PA6.6 behavior and the localization of the deformation due to the type of the considered stress. This model can also be adapted to other materials than PA6.6. [ABSTRACT FROM AUTHOR]

The manufacturing of biopharmaceutical drug solutions can involve close contact with various polymeric components, including common filter membranes. Potential leachable substances from filters may interact with the protein and thereby increase the structural damage and aggregation. The main aim of the study deals with the assessment of extractable and leachable (E/L) from different filters and the potential effect of E/Ls on protein (human granulocyte-colony stimulating factor (rh-GCSF) stability. The present study examines the E/L profile of five different polymeric filter membranes using various chromatographic techniques including LC–MS and GC–MS. In order to investigate their effect on protein stability, G-CSF (human granulocyte colony-stimulating factor) formulations were spiked with filter leachable stock solutions at two different pH levels. The spiked formulations were further analyzed with respect to their aggregation behavior. The results demonstrated a higher E/L content in the case of polyamide (PA), polycarbonate (PC), and polyethersulfone (PES) filters as compared to the polytetrafluoroethylene (PTFE) and regenerative cellulose (RC) filter materials. The E/L from RC and PES was found surface-active, whereas E/L from PA and RC significantly altered the particle size/structure resulting in the aggregation of proteins. Furthermore, bisphenol A was found to be one of the E/L substances from PC filters and can impose significant health problems when administered along with pharmaceutical products. The present study reports a qualitative rank ordering of the filter membranes in terms of their propensity to generate E/Ls and thus can be helpful in selecting a suitable membrane filter. [ABSTRACT FROM AUTHOR]

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes are widely used for the treatment of water and wastewater treatment. However, the membrane surface properties could be further modified during interfacial polymerization (IP) process to achieve higher water flux and salt rejection. Herein, the effects of sodium bicarbonate (NaHCO3) and co-amine monomer—2-(2′aminoethoxy) ethylamine (AEE) on the characteristics of piperazine (PIP)-based TFC membranes were investigated for water purification and aerobically treated palm oil mill effluent (AT-POME) treatment. Characterizations based on field emission scanning electron microscopy (FESEM), Fourier transform infrared analysis (FTIR) and contact angle were carried out to provide support to the filtration results. Our findings showed that 0.5 wt% NaHCO3 was the best loading to be added to improve the membrane performance by enhancing water permeability by 37% without affecting Na2SO4 rejection. In the presence of 0.5 wt% NaHCO3, it is found that the introduction of AEE into PIP solution could further improve the Na2SO4 rejection of PIP-based membrane from 97.1 to 98.5% while producing a permeate of better quality. Further evaluation using AT-POME indicated that the AEE-modified membrane was able to enhance the separation performance of PIP-based membrane, increasing its conductivity, colour (ADMI) and COD reduction from 74.31, 92.79 and 83.4%, respectively, to 79.15, 94.26 and 89.3%. This work demonstrated the positive features of using inorganic additive and secondary amine monomer in improving characteristics of TFC membrane for water and wastewater treatment. [ABSTRACT FROM AUTHOR]

The strain and temperature characteristics of the shape memory effect are studied in bending tests of a composite material with the nylon 66 matrix reinforced with nickel-titanium wire containing 55.7 wt % Ni. It is shown that deformation mechanisms in the matrix and the reinforcing filler influence the shape memory behavior of the composite. The В2 → В19′ martensitic transformation and dislocation slip processes occurring in nickel titanium and resulting in unrecoverable deformation determine thermomechanical properties of the composite. The plastic deformation and stress relaxation mechanisms in the polyamide matrix should also be taken into account, as they can either promote or prevent the shape memory effect in the reinforcing filler at different stages of the composite deformation. It is proposed that the main performance characteristics of shape memory composites are the critical strain εcr0.2, at which 0.2% of unrecoverable strain is accumulated, and the shape recovery start and finish temperatures determined after prestraining to εcr0.2 in a cooled state. The strain and temperature characteristics of the shape memory effect are compared between the composite material and the reinforcing filler. The viscoelastic behavior of the composite matrix is shown to decrease the critical strain from 9% in the reinforcing NiTi filler to 5% in the composite. The composite material exhibits a slight decrease (by approximately 5°C) in the shape recovery temperatures compared to the reinforcing NiTi filler. [ABSTRACT FROM AUTHOR]

This work investigates the efficiency of the Box-Behnken design (BBD) in contrast with the full-factorial design (FFD) in ultimate tensile strength (UTS) of PA12 material extrusion 3D printing (ME-3DP) specimens. Three input parameters, i.e., the raster angle (A), layer thickness (B), and nozzle temperature (C) with three levels each, were employed to compare the BBD and FFD efficiency. The 81 full-factorial UTS initial experimental data used in this research have been produced in a previous work published by the authors. Fifteen (15) out of 81 experiments were selected for the BBD design with three repetitions on the central point (0,0,0). Main effect plots (MEP), interaction plots, surface plots, ANOVA analysis, normality plots, mean absolute percentage error (MAPE), and the root-mean-square error (RMSE) evaluate the BBD and FFD approaches. The BBD MAPE and RMSE indexes show that the Box-Behnken design is appropriate for parameter analysis and processing investigation resulting in a 5.3% MAPE and 2.75 RMSE, close to 5.2% and 2.44 of the full-factorial MAPE and RMSE indexes. [ABSTRACT FROM AUTHOR]

An enhance in the manufacturing and consumption of polyamide products used in the light, food, textile, construction, engineering, and medicine industries leads to the formation of large volumes of polyamide-containing waste that must be processed and disposed of. Thermal processing of polyamides in an inert atmosphere (pyrolysis), as well as polymer degradation in the presence of atmospheric oxygen, result in the formation of a large number of organic compounds—lactams, ketones, various nitriles, as well as carcinogenic polycyclic aromatic and nitrogen-containing compounds, including valuable organic products, used for further processing. In this regard, the question arises of determining the optimal conditions for the polyamide-containing waste processing, under which the yield of valuable products increases and the amount of by-product, carcinogenic compounds, is minimized. The review describes the features of the thermal degradation of polyamides and materials based thereon in an inert atmosphere and in the presence of atmospheric oxygen and the mechanisms of depolymerization of polyamides. The influence of the polymer structure, temperature, composition of the gaseous medium, flame retardant additives, and the presence of a catalyst on the formation of degradation products in the gas and condensed phases is considered. Co-pyrolysis of polyamides with other polymers brings about an increase in the yield of gaseous products and the formation of pyrolysis oil containing a smaller amount of oxygen-containing compounds, which indicates a co-pyrolysis synergistic effect. As an example of the pyrolysis of industrial polyamide-containing waste, the process of thermal degradation of fishing net materials (both new commercial products and spent ones) is considered. [ABSTRACT FROM AUTHOR]

The right choice of porous support and diamine monomer is crucial in fabricating TFC membranes with improved performance. In this study, the effect of the supporting layer and diamine monomer structure in preparing TFC membranes for dye/salt separation was investigated. Supports used are polysulfone (PSf), polyacrylonitrile (PAN), and hydrolyzed PAN (mPAN) while diamine monomers used are piperazine (PIP), 1,3-diaminopropane (DAPE), and 1,4-bis(3-aminopropyl) piperazine (BAPP). Changing the porous substrate and monomer not only affects membrane physical and chemical morphology but also the performance of TFC NF membranes. Characterization and NF tests revealed that the TFC membrane prepared using mPAN as support and PIP as diamine monomer had most hydrophilic, roughest surface, and lowest crosslinking degree, and it delivered the optimum NF performance: J = 127.66 ± 12.61 LMH; RBrilliant Blue = 99.28 ± 0.57% RCongo Red = 99.21 ± 0.08%; RNaCl = 14.00 ± 6.16%. [ABSTRACT FROM AUTHOR]

Bearings and cylindrical roller bearings to be specific have found application in rotating machinery due to their high load-bearing ability. The dynamic performance of the bearing is greatly influenced by the contact stress, displacement, stiffness and temperature developed during service. Hence, this study employs finite element analysis software, Abaqus to determine the thermo-mechanical behaviour of a typical healthy cylindrical roller bearing of a power generation airflow root blower subjected to a dynamic load of 160 kN at 2850 r/min (300 rad/s). The contour plots and results obtained from the analysis show that the maximum temperature developed in the bearing during operation is 118.5 °C and the maximum contact stress of 896.6 MPa was developed on the outer ring, at the point of contact between the balls and the outer ring, thus making the outer ring more prone to failure as compared to the other components of the bearing during operation. [ABSTRACT FROM AUTHOR]

Carbon fiber (CF)/ polyamide (PA6) composites are one of the most promising thermoplastic materials for automobile applications. However, the interfacial adhesions between the CFs and the PA6 matrix are relatively weak, and therefore the mechanical performance of these composites, if prepared without a surface modification of CFs, is rather poor. In this study, an efficient method to improve the fiber-matrix interfacial of CF/PA6 composites based on modifications of CFs by introducing interfacial layers of PA6 is developed. In this method, the CFs are activated at 400°C in nitrogen for 4h to remove the sizing agents coated on their surface, and then they are immersed in the formic acid solution of PA6. Changes in the chemical composition, surface morphology, and mechanical properties of modified CF and its composite were investigated. Because of the strong hydrogen bond between activated CFs and PA6, the tensile strength, flexural strength, impact strength, and interlaminar shear strength (ILSS) of modified CF/PA6 increased by 24.75, 33.25, 38, and 72%, respectively. [ABSTRACT FROM AUTHOR]

The safe application of nanoparticles in water treatment processes is a growing concern globally, making the utilisation and deployment of appropriate support materials necessary. Hydrothermally synthesised β-FeOOH nanoparticles were incorporated into the polyamide matrix via an in-situ method to fabricate catalytic composites. The materials elucidation was effected using SEM, TEM, ATR-FTIR, XRD and nitrogen adsorption–desorption. The heterogeneous catalytic property of the β-FeOOH/polyamide nanocomposites was evaluated in an aqueous ozonation system with 4-chlorophenol (4CP) as the target organic pollutant. Aliquots were drawn at different time intervals and analysed by LCMS-TOF. The results showed high degradation of 4CP (98.52%) within 40 min compared with ozonation (62.94%). The degradation of 4CP under pH 3, 7 and 10 gave efficiencies of 83.56%, 90.16% and 96.01%, respectively, at 30 min. The composite exhibited excellent reuse potential over six cycles, with no iron leaching observed at different pH conditions. The chemical oxygen demand (COD) and total organic carbon (TOC) for natural wastewater were reduced by 54.62% and 89.22% respectively using the polymeric nanocomposites, while the optimum treatment duration was established using ecotoxicity assessment of the treated water. The novel composites gave excellent removal of 4CP from aqueous solutions. [ABSTRACT FROM AUTHOR]

Melt post-condensation and thermal and thermo-oxidative degradation of a cycloaliphatic polyamide (Trogamid™ CX7323) were studied through time-resolved rheometry (TRR). The implemented TRR elucidates structural changes occurring during the two concurrent phenomena, namely, melt post-condensation and thermal/thermo-oxidative degradation, during the time sweep in a parallel plate rheometer. TRR measurements were conducted on neat Trogamid™ under nitrogen (inert/non-oxidative) and air (oxidative) environment at 3% strain amplitude and a range of frequencies between 0.1 and 100 rad/s for a duration of 2 h. The linear viscoelastic properties of the transparent polyamide showed an exponential increase with time at 255 ºC under both oxidative and non-oxidative environments, suggesting an increase in molecular mass. At temperatures of 260, 270, and 275 ºC, a dual-stage time-dependent growth in viscoelastic properties was observed under an oxidative environment. Thermo-oxidative degradation of the polymer melts at 270 ºC occurs from the exposed edge of the sample, continuing inwards, effectively reducing the radius of the unoxidized polymer melt by 6.4% from its initial value of 12.5 mm. In the dual-stage growth, the first exponential growth is attributed to post-condensation with continuous desorption of water, followed by logistic oxidative degradation. Furthermore, a new methodology is presented to interpret and differentiate the rheological behavior of the bulk polymer melt from the oxidized segment present within the volume of the test sample. [ABSTRACT FROM AUTHOR]

Polyamide thin film composite membranes have dominated current reverse osmosis market on account of their excellent separation performances compared to the integrally skinned counterparts. Despite their very promising separation performance, chlorine-induced degradation resulted from the susceptibility of polyamide toward chlorine attack has been regarded as the Achilles's heel of polyamide thin film composite. The free chlorine species present during chlorine treatment can impair membrane performance through chlorination and depolymerization of the polyamide selective layer. From material point of view, a chemically stable membrane is crucial for the sustainable application of membrane separation process as it warrants a longer membrane lifespan and reduces the cost involved in membrane replacement. Various strategies, particularly those involved membrane material optimization and surface modifications, have been established to address this issue. This review discusses membrane degradation by free chlorine attack and its correlation with the surface chemistry of polyamide. The advancement in the development of chlorine resistant polyamide thin film composite membranes is reviewed based on the state-of-the-art surface modifications and tailoring approaches which include the in situ and post-fabrication membrane modifications using a broad range of functional materials. The challenges and future directions in this field are also highlighted. [ABSTRACT FROM AUTHOR]

A novel method to enhance antibacterial activity, thermophysiological comfort properties of highly elastane polyamide 66 fabrics by calcium chloride pad-dry-cure method was proposed. For this purpose, three different calcium chloride solutions were prepared and applied by pad-dry-cure method to the polyamide tricot (locknit) warp knitted fabrics. The effects of this method on polyamide fabrics were investigated by antibacterial activity, thermophysiological properties, physical performance tests and characterization analyses, namely, SEM, EDX and FTIR-ATR. Results indicate that calcium chloride agent procedure significantly affected antibacterial activity and thermal comfort properties. The calcium chloride agent procedure was found to be favorable for polyamide/elastane fabrics since it provided antibacterial activity and thermophysiological effect under mild conditions with good stiffness, handle and whiteness properties by means of calcium chloride ionic bonds onto polyamide/elastane fabrics. Most notably, calcium chloride treated fabrics were evaluated as good antibacterial, extremely breathable and comfortable at a higher level of activity. [ABSTRACT FROM AUTHOR]

Surfactants modified the property and performance of polyamide layer during interfacial polymerization of amines and trimesoyl chloride. In this work, three types of similar chain length surfactants with different charge and hydrophile-lipophile (HLB) value was used as additive separately in fabrication of nanofiltration-like forward osmosis membrane. These surfactants are sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB), and sorbitan monolaurate (Span 20). The negatively charged SDS interacted with amines and polyamide layer through electrostatic interaction and hydrogen bonding. It also facilitated the transport of amine into the organic phase by reducing the interfacial tension on the immiscible interface of water and n-hexane. Adding SDS into the amine solution could convert the membrane into more positively charged surface, and a membrane with low water flux. DTAB, a cationic surfactant only interacted with the polyamide layer through electrostatic interaction between its quaternary amine and carboxyl groups of polyamides. In addition, it also changed the membrane into more hydrophilic and negatively charged polyamide layer, leading to higher water flux and low salt reverse flux of TFCDTAB. On the other hand, Span 20, a neutral surfactant that is not completely soluble because of its low HLB value, only dispersed in the amine solution leading to poor membrane performance. In the forward osmosis test (pressure-retarded osmosis mode), TFCDTAB delivered the highest membrane performance using 1 M Na2SO4 draw solution and deionized water as feed: 63.23 ± 2.24 L·m−2·h−1 and the salt reverse flux of 17.83 ± 2.18 g·m−2·h−1. Therefore, a suitable surfactant is needed to regulate the performance of the membrane. [ABSTRACT FROM AUTHOR]

The principal intention of this work is to fabricate and characterize the polyamide/chitosan nanocomposite by a novel single solvent method through the electrospinning procedure. The thermal properties and morphology of prepared nanocomposite are studied by thermogravimetric analysis (TGA) and field-emission scanning electron microscopy (FE-SEM). TGA exposed that the primary decomposition temperature is reduced with rising of chitosan content in the nanocomposites and origin disintegration temperature for polyamide/chitosan nanocomposites is perceived to be in the range from 300 to 500 °C. Also, FE-SEM images demonstrated that the nanofibers of chitosan have good adhesion on the matrix and are well-oriented. Besides, the crystallinity and structural characteristics of the polyamide/chitosan nanocomposites are investigated by using X-ray diffraction (XRD) and Fourier transform-infrared spectroscopy (FT-IR), respectively. The results of XRD proved that the successful blending of chitosan in polyamide is achieved via the electrospinning method. FT-IR results demonstrate that the nanofibers are consist of amine groups. Also, the electrical properties of the nanocomposite improved with the increasing content of chitosan and the conductivity of the polyamide/chitosan 5 wt% demonstrates the maximum current of 0.3 nA. Besides, the sheet resistance of the composite reduced 118–20 × 109 Ω/□ with raising the chitosan volume from 0 to 5 wt%. [ABSTRACT FROM AUTHOR]

In this context, carbon nanotubes (CNTs)/silver nanoparticles hybrids with special 1-dimensional–0-dimensional (1D–0D) structure were successfully fabricated via self-assemble of dopamine followed by reduction reactions of silver cations aiming to synthesize more efficient thermal conductive fillers for the formation of heat flow transfer network in PA6 matrix. FTIR, XRD, TG and TEM revealed the characteristics of functionalized CNTs. Meanwhile, the effect of CNTs hybrids with 1D–0D structure on the construction of heat flow network and thermal conductivity was also investigated. Experimental results showed that thermal conductivity of composites enhanced with increased filler content, the highest thermal conductivity of the PA6/CNTs hybrids composites reached 0.65 W m−1 K−1, which was 2.1 times that of pure PA6 and 32% higher than that of pristine CNTs-filled composites (0.55 W m−1 K−1) with same filler content (10 vol%), and this was ascribed to the better dispersion of fillers and enhanced interfacial interaction between fillers and matrix, as well as the special structure of CNTs hybrids that could abundance the heat transfer path. The crystallinities and dynamic thermal mechanical properties were also analyzed. The enhanced storage modulus (1940 MPa for pure PA6 to 3650 MPa for PA6/CNTs hybrids composites at 5 °C) and higher glass transition temperature along with the change of crystallization behavior of fabricated composites were in accordance with the thermal conductive behavior. The thermal conductive model and its mechanism were then proposed and further confirmed by scanning electron microscopy. [ABSTRACT FROM AUTHOR]