Polyamide Resin Research Articles

Identification of mechanisms and experimental implementation for enhancing the interfacial force between oxygen functionalized waste carbon fibers and polyamide resin

To recycle waste carbon fibers (CFs) and utilize them as a composite material with polyamide–6 (PA–6), the oxidation of the carbon surface is crucial for enhancing its bonding with PA–6 without damaging the waste CFs. However, the most effective oxygen-containing functional group (O–group) was hitherto unknown. In this study, computational simulations demonstrated that incorporating O–groups enhanced the interfacial bonding force via hydrogen bonding between the oxygen of the O–groups and hydrogen (N–H) of PA–6. Among various O–groups, the bonding of lactone groups to PA–6 was energetically most favorable, corroborated by different oxidation treatments such as acid, heat, and plasma. As the reaction time or temperature increased, the amount of O–groups, such as lactones, increased. Regardless of the oxidation treatment type, an increase in the amount of O–groups increased the interfacial force, and this tendency was predominantly observed in lactone groups. However, excessive surface oxidation introduced defects on the surface of CFs, which reduced the interfacial force. The modification of waste CFs by identifying the proposed mechanisms lays the groundwork for synthesizing high-quality waste CF composites.

Development of anti-corrosion coating with sandwich-like microvascular network for realization of self-healing and self-reporting properties based on coaxial electrospinning

Biomimetic microvascular networks prepared by coaxial electrospinning technology have attracted much attention as a novel form of carrier for encapsulating active substances. However, the poor interfacial bonding strength between traditional electrospinning materials and metal substrates limits its application in anti-corrosion coatings. Herein, a novel poly(vinyl alcohol) grafted phytic acid (PVA-PA) electrospinning solution was synthesized. And a sandwich-like microvascular network (SMN) was prepared by coaxial electrospinning technology, which used PVA-PA solution as the shell material, epoxy resin 51 (E51), tetraphenylethylene (TPE) and polyamide resin as the core materials, respectively. Owing to the high porosity of SMN, epoxy resin can be directly spin-coated on it to form a composite coating (PVA-PA/SMN/EP). It is proved that due to the strong chelation and coordination interaction between PA and mild steel, the pull-out adhesion of the PVA-PA/SMN/EP composite coatings on mild steel was increased by 0.92 MPa. In addition, by systematically optimizing the relative viscosity, miscibility, conductivity, and saturated vapor pressure between the two jets of the core solution and the shell solution in coaxial electrospinning, the microvascular structure of the coaxial electrospinning nanofibers was improved and the fluidity of the internal active substances was maintained. When the PVA-PA/SMN/EP composite coating generates microcracks, the active substances encapsulated in the SMN flow out, in which the three-dimensional crosslinked network formed by the curing of E51 and polyamide resin enhances the spatial interactions between TPE molecules, which results in TPE emitting a bright blue fluorescence. This work provides a new approach for the development of the next generation of smart anti-corrosion coatings.

Rheological Property Modification of a Molten-State Polyamide through the Addition of an α-Olefin-Maleic Anhydride Copolymer.

The rheological properties of a polyamide (PA) resin with low crystallinity were modified by melt-mixing it with a small amount of an alternative α-olefin-maleic anhydride copolymer as a reactive compound. Because PA has a low melting point, rheological characterization was performed over a wide temperature range. Owing to the reaction between PA and the alternative α-olefin-maleic anhydride copolymer, the blend sample behaved as a long-chain branched polymer in the molten state. The thermo-rheological complexity was obvious owing to large flow activation energy values in the low modulus region, i.e., the rheological time-temperature superposition principle was not applicable. The primary normal stress difference under steady shear was greatly increased in the wide shear rate range, leading to a large swell ratio at the capillary extrusion. Furthermore, strain hardening in the transient elongational viscosity, which is responsible for favorable processability, was clear. Because this is a simple modification method, it will be widely employed to modify the rheological properties of various polyamide resins.

Size Effect of Graphite Nanosheet-Induced Anti-Corrosion of Hydrophobic Epoxy Coatings

In order to broaden the selectivity of graphite nanosheet additives on epoxy resin-based coatings and verify the size effect, this work aims to dope graphite nanosheets of different sizes into the three-dimensional structure produced by cross-linking and curing epoxy resin and polyamide resin. In addition, a micro-nano level secondary structure and a surface with special roughness are constructed to obtain the composite epoxy hydrophobic coating. The influence of the size effect of graphite nanosheets on the hydrophobic performance and corrosion resistance of the coating is summarized as well. Among them, the optimized doping size (2.2 μm) of graphite nanosheets in the epoxy coating showed the largest impedance arc of 2.58 × 108 Ω cm2, which could form an excellent nano-network covering the micropores to impede the diffusion of corrosive medium. Through simulation calculation analysis, we also found that the edge site of graphene is more effective in capturing H2O and O2; therefore, a smaller size of graphene with a large edge can be more favorable. This work will be used as a reference for the industrial application of graphite anti-corrosive coating.

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

AbstractHydrogen bonding is the prerequisite for polyamide fibers to have better stress–strain behavior. It affects the crystal structure of polyamide fibers, such as orientation and periodic arrangement. To illustrate the effect of intermolecular hydrogen bonding on fiber orientation structure and macroscopic mechanical properties, this work uses conventional polyamide resin doped with high molecular weight components to construct polymer compounds with discrete distribution characteristics. By analyzing the changes in intermolecular hydrogen bonds, melt rheological properties, non‐isothermal crystallization behaviors, the impact of hydrogen bonds on the crystal structure and orientation structure and thus on the fiber strength was clarified. The doping of high molecular weight components can make the compound form more hydrogen bonds and inhibit the relaxation of molecular chains through entanglement, thereby promoting melt non‐isothermal crystallization process and increasing complex viscosity η* and storage mode G'. 1D and 2D wide‐angle and small‐angle X‐ray scattering show that doping components reduce crystal size of α1(200) and α2(002, 202) planes from 4.19 to 3.47 nm and 5.88 to 4.96 nm, resulting in a denser long‐period structure. Through the strategy of this work, polyamide 6 fibers' tensile strength is effectively improved by18%, and the mechanical properties are significantly improved.Highlights High‐strength polyamide compound fibers were prepared. Discretely distributed compounds are achieved. Discretely distributed molecular weight enabled hydrogen bonding regulation. Hydrogen bonding‐induced compound fiber crystal structure. Multiple external fields induced crystallization and orientation structures.

Anti-pulmonary fibrosis activity analysis of methyl rosmarinate obtained from Salvia castanea Diels f. tomentosa Stib. using a scalable process.

Pulmonary fibrosis is a progressive, irreversible, chronic interstitial lung disease associated with high morbidity and mortality rates. Current clinical drugs, while effective, do not reverse or cure pulmonary fibrosis and have major side effects, there are urgent needs to develop new anti-pulmonary fibrosis medicine, and corresponding industrially scalable process as well. Salvia castanea Diels f. tomentosa Stib., a unique herb in Nyingchi, Xizang, China, is a variant of S. castanea. and its main active ingredient is rosmarinic acid (RA), which can be used to prepare methyl rosmarinate (MR) with greater drug potential. This study presented an industrially scalable process for the preparation of MR, which includes steps such as polyamide resin chromatography, crystallization and esterification, using S. castanea Diels f. tomentosa Stib. as the starting material and the structure of the product was verified by NMR technology. The anti-pulmonary fibrosis effects of MR were further investigated in vivo and in vitro. Results showed that this process can easily obtain high-purity RA and MR, and MR attenuated bleomycin-induced pulmonary fibrosis in mice. In vitro, MR could effectively inhibit TGF-β1-induced proliferation and migration of mouse fibroblasts L929 cells, promote cell apoptosis, and decrease extracellular matrix accumulation thereby suppressing progressive pulmonary fibrosis. The anti-fibrosis effect of MR was stronger than that of the prodrug RA. Further study confirmed that MR could retard pulmonary fibrosis by down-regulating the phosphorylation of the TGF-β1/Smad and MAPK signaling pathways. These results suggest that MR has potential therapeutic implications for pulmonary fibrosis, and the establishment of this scalable preparation technology ensures the development of MR as a new anti-pulmonary fibrosis medicine.

Advanced optical photothermal infrared spectroscopy for comprehensive characterization of microplastics from intravenous fluid delivery systems

Growing attention is being directed towards exploring the potential harmful effects of microplastic (MP) particles on human health. Previous reports on human exposure to MPs have primarily focused on inhalation, ingestion, transdermal routes, and, potentially, transplacental transfer. The intravenous transfer of MP particles in routine healthcare settings has received limited exploration in existing literature. Standard hospital IV system set up with 0.9 % NaCl in a laminar flow hood with MP contamination precautions. Various volumes of 0.9 % NaCl passed through the system, some with a volumetric pump. Fluid filtered with Anodisc filters washed with isopropyl alcohol. The IV cannula was immersed in Mili-Q water for 72 h to simulate vein conditions. Subsequently, the water was filtered and washed. Optical photothermal infrared (O-PTIR) microspectroscopy is used to examine filters for MP particles. All filters examined from the IV infusion system contained MP particles, including MPs from the polymer materials used in the manufacture of the IV delivery systems (polydimethylsiloxane, polypropylene, polystyrene, and polyvinyl chloride) and MP particles arising from plastic resin additives (epoxy resin, polyamide resin, and polysiloxane-containing MPs). The geometric mean from the extrapolated result data indicated that approximately 0.90 MP particles per mL of 0.9 % NaCl solution can be administered through a conventional IV infusion system in the absence of a volumetric pump. However, with the implementation of a pump, this value may increase to 1.57 particles per mL. Notably, over 72 h, a single cannula was found to release approximately 558 MP particles including polydimethylsiloxane, polysiloxane-containing MPs, polyamide resin, and epoxy resin. Routine IV infusion systems release microplastics. MP particles are also released around IV cannulas, suggesting transfer into the circulatory system during standard IV procedures.

Optimization of flavonoids extracted from hawthorn （Crataegus pinnatifida） by ultrasonic-assisted deep eutectic solvent

Hawthorn flavonoids have received extensive attention in agriculture, pharmaceutical and food industries due to their rich biological activities. In this study, deep eutectic solvent (DES) was used to extract flavonoids from hawthorn. Under optimal conditions, with a molar ratio of ethylene glycol to choline chloride at 2:1, DES volume fraction 70%, the solid-liquid ratio of 30:1 (mL/g), and an Ultrasound time of 30 min, the yield of hawthorn flavonoids was 57.82 ± 0.04 mg/g. The measured results were consistent with the prediction. After extracting hawthorn flavonoids, DES was recovered by polyamide resin. The recovery rate reached 91.53% ± 0.12%. Finally, HPLC method was used to compare the content and composition of hawthorn flavonoids extracted by DES compared with ethanol. The experimental results showed that DES had a higher yield and a slightly different composition from ethanol-assisted ultrasonic extraction. In conclusion, the deep eutectic solvent has good application prospects in extracting hawthorn flavonoids.

Compression performance of 3D-printed thermoplastic auxetic structures

The influence of lattice structural design on the mechanical property has been abundantly investigated, however, the effect of material on the load-carrying performance and energy absorption was seldom studied. In the current work, the auxetic structures fabricated using four materials including polyamide (PA), carbon fiber (CF) reinforced PA (PA/CF), polyether ether ketone (PEEK) and PEEK/CF were 3D-printed, and the compression performance and deformation behavior were compared and explored. The results showed that the deformation mode of auxetic structure were similar, which was not dependent on the material type. However, the compressive strength and modulus of the auxetic structure showed strong dependence on the material properties. Besides, PA and PA/CF auxetic structures displayed better rebound behavior after compression, which was perhaps attributed to the good resilience of PA resin. Therefore, mathematical equations were utilized to predict the compressive property based on the material parameters, showing a good agreement. On the other hand, the simulation of compression process was established and conducted, which confirmed the deformation process as experimental presented. The rebound behavior was further predicted by a loading-releasing cycle with different compression strains. Accordingly, the compression parameters showed great relations with material parameters but little effect on the deformation behavior.

Novel efficient epoxy resin based shielding materials enhanced with BN powder against nuclear radiation: A new perspective of shielding performance analysis

In this work, novel efficient epoxy resin based shielding materials enhanced with BN powder against nuclear radiation was proposed. The composites were prepared by using epoxy resin E51, polyamide resin 651 and BN powder. Neutron shielding performance was analyzed by using Evaluated Nuclear Data File, partial density method and a moderated 241Am–Be neutron source. In addition, gamma ray shielding performance and mechanical property were tested by a137Cs gamma ray source and an electronic universal testing machine, respectively. The results indicate that the addition of BN powder could improve the shielding performance for thermal neutron, fast neutron and gamma ray. Neutron shielding performance of prepared composite materials is nearly the same with the variation of densities. Nuclear shielding performance is better than commercial shields (SWX-213, SWX-201 and SWX-261). And the bending strength is greater than 12.78 MPa. In addition, shielding attenuation mechanism for neutron at 10−5–2 × 108 eV is mainly contributed by elastic scattering attenuation interaction produced by H and C from epoxy resin matrix, and absorption attenuation interaction produced by B from BN powder at 10−5–102 eV.

Synthesis of biomass hyperbranched polyamide resin from cellulose and citric acid for wood adhesive

Traditional wood adhesives have the problems of excessive dependence on fossil resources and environmental pollution. Cellulose, a renewable biomass resource with a low price and huge output, provides a basis for preparing biomass wood adhesives. In this study, a new type of polyamide resin was prepared by modifying microcrystalline cellulose and reacting with natural citric acid. Specifically, toluenesulfonyl cellulose (TS) was synthesized, and functional amino cellulose (AC) was prepared by a nucleophilic substitution reaction with hyperbranched polyamide (HP). Then cellulose-based hyperbranched polyamide resin (CHP) was prepared by polycondensation with citric acid. The structure of CHP resin was investigated by FTIR, XPS, 13C NMR and GPC, and plywood was prepared to study its mechanical properties. Due to the formation of hyperbranched cross-linked network structure inside the resin, the prepared plywood has excellent properties. The dry shear strength reaches 2.24 MPa, and the strength reaches 1.25 and 1.31 MPa after soaking in water at 63 °C and 93 °C for 3 h. The resin in this study has a simple preparation process and excellent performance, which provides a solid foundation for developing high-performance cellulose-based wood adhesives.

An investigation into mechanical properties of a 3D printed two-matrix continuous fiber composites with multi-cavity structure

A continuous fiber reinforced two-matrix composites with multi-cavity structure was fabricated by a co-extrusion method, combining the excellent wettability of thermosetting resin to fiber and the wonderful extrusion forming ability of thermoplastic for nozzle based additive manufacturing (AM). Diversified component materials were utilized to enrich database for the AM of continuous fiber composites, including continuous carbon fiber (CCF), continuous basalt fiber (CBF), short fiber reinforced polyamide (SFRPA), polyamide (PA), polylactic acid (PLA) and epoxy resin. The tensile and flexural tests were conducted to investigate the effect of component materials on the mechanical properties. The micro-structures of printing filament and the fracture morphology of samples were characterized by optical microscope (OM) and scanning electron microscopy (SEM), respectively. A novel numerical model based on Peridynamics (PD) was proposed for the simulation of failure model. The three-dimensional (3D) printed continuous fiber reinforced two-matrix composites with multi-cavity structure show dissimilar mechanical behavior and failure characteristic for different combinations of component materials. The micro-structure of the fiber bundle pre-impregnated by epoxy resin after printing has a great influence on the mechanical properties and fracture modes of the samples. The failure modes mainly include pullout and breakage of fiber, stress whitening and crack of matrix, and interfacial debonding. The PD model effectively captures the tensile and flexural failure characteristic of 3D printed composites with multi-cavity structure. The results from experimental analysis and numerical simulation have reference significance for structural optimization and failure prediction of continuous fiber composites printed by co-extrusion process.

Influence of silane interfacial chemistry on the curing process of anionic Polyamide 6 in glass reinforced composites

The manufacturing of composites based on reactive thermoplastic polyamide 6 (PA6), reinforced with glass particles or fibers for structural applications, is quite sensitive to the state of the interface. Surface hydroxyls present at the glass surface can completely inhibit both the PA6 polymerization and crystallization processes. Care must then be exerted when tuning the interfacial chemistry in this system. This work demonstrates how an adequate choice of silane coupling agent, combined with a precise surface grafting methodology and tight control of hydroxyl groups density on glass particulates, yields kinetics and degrees of polymerization and crystallization comparable to the pure PA6 resin. Various silanes were grafted onto the microparticles and their surfaces were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, confocal laser scanning microscopy and contact angle measurements. The activator was also grafted onto the glass surface to initiate polymerization directly from the surface. The results showed that all treated glass particles surfaces allowed obtaining a high degree of conversion but with varying polymerization and crystallization kinetics. The results provide fundamental information on the role of the surface chemistry of glass reinforcements on the polymerization and crystallization of PA6, which are essential for the proper control of composite manufacturing.

Evaluación de un antimicrobiano sobre la adhesión de Candida albicans a materiales de prótesis dentales

Objective: to evaluate the effect of AlphaSan® on C. albicans adhesion to acrylic and polyamide resins. Methods: 2 x 2 mm squares were made with acrylic resin (AR) and polyamide resin (PR). Four study groups (n=12) were established: Group A: AR without AlphaSan®, Group B: AR with AlphaSan®, Group C: RP without AlphaSan®, Group D: RP with AlphaSan®. All groups were incubated in BHI broth with C. albicans ATCC at 36°C for 48 hours. Quantification of fungal adherence was performed by confocal microscopy (CM) and by means of an aqueous solution of crystal violet (CV), measuring the absorbance at 570 nm. Results: In the quantification of C. albicans adherence with CM, a 50% decrease (p =0.03) was observed between the treated groups (B and D) in relation to those not treated with AlphaSan® (A and C). No significant difference in C. albicans adherence was found between groups B and D (p > 0.5). C. albicans adherence, by CV, decreased by 55% (p= 0.01) in AR with AlphaSan® compared to AR without AlphaSan®. On the other hand, it was observed that fungal adherence decreased by 61% (p=0.01) in RP with AlphaSan® compared to RP without AlphaSan®. No significant difference was observed between the samples treated with the antifungal studied (p >0.05). Conclusion: Fungal adherence to the materials treated with AlphaSan® was limited to 50%, this would be due to the fact that the fungus presents a rigid cell wall (glucans and chitin), which provides a physical barrier for the penetration of different compounds. Consequently, it could be assumed that AlphaSan® would act on the cell wall, which would result in 50% of the fungi being able to adhere to the dental materials.

Preparation and characterization of morphological and mechanical properties of cellulose cryogel nanofibers reinforced by different polyamide resins

Preparation and characterization of morphological and mechanical properties of cellulose cryogel nanofibers reinforced by different polyamide resins

Effect of cigarette smoke and denture cleansers on the surface properties and color stability of CAD-CAM and conventional denture base resins.

This study aimed to evaluate the hardness, roughness, and color stability of heat- and microwave-polymerized polymethyl methacrylate (PMMA), polyamide, and CAD-CAM PMMA resins when exposed to cigarette smoke (CS) and immersed in a denture cleanser (DC). Specimens of each resins were divided into four subgroups (n=10). The DC and CS+DC specimens were immersed in a DC; the CS and CS+DC specimens were exposed to CS; and the control (C) specimens were kept in distilled water. Hardness, roughness, and color measurements were performed. DC and CS significantly affected the roughness and color of all resins (p<0.05). However, these did not affect the hardness of the CAD-CAM PMMA resin (p>0.05). The CAD-CAM PMMA resin presented the lowest roughness, highest hardness, and lowest ΔE00 values. While the roughness of all resins exposed to CS when immersed in DC decreased, the ΔE00 values of the conventional PMMAs also decreased. Although this decreases were not significant, it may be advisable to use DC for smokers to decrease discoloration and roughness especially for conventional PMMAs resins.

Development of a food preservative from sea buckthorn together with chitosan: Application in and characterization of fresh-cut lettuce storage.

The purpose was to create a novel composite food preservative for fresh-cut lettuce using flavonoids and chitosan from sea buckthorn leaves (SBL). Sea buckthorn leaves were extracted with ethanol as the extraction solvent and ultrasonic-assisted extraction to obtain flavonoid from sea buckthorn leaf crude (FSL), and then the FSL was secondarily purified with AB-8 resin and polyamide resin to obtain flavonoid from sea buckthorn leaf purified (FSL-1). Different concentrations of FSL-1 and chitosan were made into a composite preservative (FCCP) by magnetic stirring and other methods, containing 1% chitosan preservative (CP) alone, 0.5-2 mg/ml of FSL-1 and 1% chitosan composite preservative (FCCP-1, FCCP-2, FCCP-3, and FCCP-4), and the FSL-1 concentrations were analyzed the effect of FSL-1 concentration on the physicochemical properties of the composite preservatives, including their film-forming ability, antioxidant capacity and ability to prevent bacterial growth, was analyzed. To further investigate the effect of the combined preservatives on fresh-cut lettuce, different FCCPs were applied to the surface was stored at 4°C for 7 days. Then the changes in weight loss, hardness, browning index, total chlorophyll content, SOD and MDA were analyzed. It was used to assess the physicochemical indicators of fresh-cut lettuce throughout storage. According to the results of Fourier transform infrared spectroscopy, FSL-1 and chitosan interacted to form hydrogen bonds, and the contact angle and viscosity of FCCP increased on both horizontal glass and polystyrene plates, indicating the good film-forming properties of the composite preservation solution. With the diameter of the antibacterial zone of Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes being (21.39 ± 0.22), (17.43 ± 0.24), (15.30 ± 0.12), and (14.43 ± 0.24) mm, respectively. It was proved that the antibacterial activity of FCCP became stronger with the increase of FSL-1 concentration and had the best antibacterial effect on S. aureus. The complex preservative showed the best scavenging effect on ferric reducing antioxidant capacity, DPPH radicals (96.64%) and 2,2'-Azinobis- (3-ethylbenzthiazoline-6-sulphonate) (ABTS) radicals (99.42%) when FSL-1 was added at 2 mg/ml. When fresh-cut lettuce was coated with FCCP for the same storage time, various indicators of lettuce such as weight loss, hardness, browning index, SOD activity and MDA content were better than the control group showing good potential in fresh-cut vegetables and fruits preservation. FCCP holds great promise for food safety quality and shelf-life extension as a new natural food preservative. The waste utilization of sea buckthorn leaves can greatly improve his utilization and economic benefits.

Browning inhibition and shelf life of packaged air‐dried chestnut kernels

AbstractAir‐dried chestnut is a traditional snack in northern China, but no standardized quality control methods or commercial products are available. The browning of air‐dried chestnut kernels was inhibited by the combined use of 1.5% EDTA‐2Na, 1% pullulan, and 1% l‐cysteine. The air‐dried chestnut kernels were packed in three different bags (PB1, polyethylene (PE); PB2, polyamide resin (PA)/PE; and PB3, polyethylene terephthalate/PA/aluminum foil/PE), and stored at 4°C, 25°C, and 35°C, respectively. With increased storage time, the degree of browning, weight loss, and hardness increased, while the antioxidant activity and respiration rate decreased. The shelf life (SL) of packaged air‐dried chestnut kernels in different storage conditions was predicted by the Arrhenius equation, and the longest predicted shelf‐lives at 4°C, 25°C, and 35°C were 105.3 days (PB2), 19.5 days (PB3), and 10.8 days (PB1), respectively. The results provide guidance for inhibiting the browning of packaged air‐dried chestnut kernels and prolonging their SL during production and consumption.Practical applicationsAir‐dried chestnut has a crisp and sweet taste and low digestibility of starch, however, it has not been industrially processed until now. The optimal browning inhibitors and packaging materials of air‐dried chestnut kernel were explored, and the shelf life of packaged air‐dried chestnut kernel was predicted using Arrhenius equation. The results of this study will be beneficial to the commercial production of air‐dried chestnut kernel.

Shell structure control of monodisperse polystyrene‐silver composite microspheres and synthesis of epoxy resin‐based anisotropic conductive adhesives

AbstractMonodisperse polystyrene‐silver (PS‐Ag) composite microspheres were used to enhance the electrical conductivity of epoxy resin‐based anisotropic conductive adhesives (ACAs). Specially designed PS‐Ag composite microspheres were used as conductive elements to construct anisotropic conductive arrays. In addition, the surface microstructure and morphology of PS‐Ag composite microspheres were controlled by adjusting the silver precursor concentration and implemented electroless plating method. The size and conductivity of the final composite microspheres used for ACAs were 2.572 μm and 81,967 S cm−1, respectively. In addition, diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin and polyamide resin were used as the matrix resin and curing agent, respectively, to predict the optimum curing process parameters based on curing kinetics. Based on this premise, carboxyl‐terminated butadiene‐acrylonitrile (CTBN) and PS‐Ag composite microspheres were used as the toughening agent and conductive filler, respectively, and a facile strategy was developed to prepare ACAs (viz., PS‐Ag/Ep‐ACAs). As the PS‐Ag composite microspheres exhibited a submicron structure, PS‐Ag/Ep‐ACAs creatively exhibited satisfactory anisotropic electrical and mechanical properties. Therefore, the research strategy and fabrication methods proposed demonstrate immense potential for the fabrication of large‐scale ACAs in practical applications.

Microplastics pollution in the river Karnaphuli: a preliminary study on a tidal confluence river in the southeast coast of Bangladesh.

Bangladesh is a deltaic country in Asia, and its riverine systems ultimately drain into the Bay of Bengal. Plastic is a severe environmental issue for coastal-marine ecosystems due to the indiscriminate usage and discarding of plastic items in the upstream river that eventually find their route into the Bay of Bengal. Microplastics (MPs)are widespread pollutants in almost all environmental compartments, including aquatic environments. This study aimed to quantify and understand the distribution of microplastics in surface water and sediments of the river Karnaphuli, a tidal confluence river adjacent to the Chattogram seaport city of Bangladesh, a highly inhabited and industrial area on the southeast coast of the Bay of Bengal. A manta trawl net (300-µm mesh size) was used to collect surface water samples, while an Ekman dredge was used to collect sediment samples. The concentrations of microplastics in the surface water of the river Karnaphuli during late monsoon, winter, and early summer were recorded to be 120,111.11, 152,222.22, and 164,444.44 items/km2, respectively, while in sediments, those were recorded to be 103.83, 137.50, and 103.67 items/kg, respectively. A higher abundance of microplastics was observed in downstream surface water (228,888.88 items/km2) and sediments (164.17 items/kg). Smaller sizes (0.3 to 0.5mm) of microplastics were predominant, fibers or threads were the frequent types, and black was the most common color in the river Karnaphuli. The Fourier transform infrared analysis revealed that polyethylene terephthalate (surface water: 22%, sediments: 19%), polyamide (surface water: 15%, sediments: 13%), polyethylene (surface water: 12%, sediments: 18%), polystyrene (surface water: 13%, sediments: 11%), and alkyd resin (surface water: 13%, sediments: 10%) were the most prevalent polymers in the river Karnaphuli. Moreover, there was a moderate positive correlation between MPs abundance in surface water and sediments. Therefore, improved long-term research (in different seasons with horizontal and vertical monitoring) is necessary in order to accurately determine the flux of microplastics from the river Karnaphuli to the Bay of Bengal.