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The development of composite materials with excellent thermal conductivity is attracting extensive attention to meet the increasing heat concentration challenges in both power and electronic equipment. Previous strategies for improving the thermal conductivities usually accompanied by the cost of mechanical strength. Herein, we propose a new strategy for developing both mechanically strong and thermally conductive composite films. The aramid nanofibers (ANF) are well prepared with introducing Ag nanoflakes and graphene oxide (GO) via vacuum-assisted filtration and hot-pressing treatment. Results indicate the synergistic effects of low dimension materials have resulted in a tightly arranged phonon network construction. The in-plane thermal conductivity of the prepared ANF/Ag/GO film reaches 9.84 W m−1 K−1, about 371% higher than that of pure ANF. Meanwhile, the strong hydrogen bond formed between the functional group of GO and the amide group of ANFs plays a synergistic strengthening and toughening role at the complex interface, and the tensile strength reaches 231 MPa. We believe that these findings shed some light on the design and fabrication of multifunctional materials for thermal management applications. [ABSTRACT FROM AUTHOR]

Monolithic silica-based aerogels, produced with tetraethoxysilane (TEOS), reinforced with aramid fibers and incorporating aluminosilicates were prepared for the first time. The nanocomposites were obtained by varying the amount and type of aramid fibers and replacing a part of the synthetic Si (up to 35 wt% of Si) of TEOS by natural aluminosilicates, kaolin and palygorskite. The effects of the type and amount of both fiber and mineral in the materials key properties were investigated. Most samples displayed very low volumetric shrinkages during ambient drying (<5%), high porosity (∼90%), and low bulk densities, down to 120 kg m−3. Composites with both minerals exhibited superinsulating thermal performance, with thermal conductivity reaching values as low as 22 mW m−1 K−1, while also showing excellent thermal stability. The mechanical properties of the designed clay mineral-silica aerogels can be tailored, since the addition of short length fibers (Kevlar pulp) produces stiffer composites, while the longer fibers (Teijinconex) lead to more flexible ones. [ABSTRACT FROM AUTHOR]

The incorporation of microcapsule particles (MPs) into fabrics offers the potential to enhance both the friction between fabric yarns and the bulletproof impact performance. In this study, MPs were prepared using the interfacial polymerization method. Furthermore, an innovative modification of the AF fabric was achieved by introducing a silane coupling agent and MPs. This resulted in the development of a microcapsules‐aramid fibers (MPs‐AF) composite material exhibiting excellent protective performance. The characterization experiment demonstrated the successful adhesion of MPs to the AF fabric, forming a robust bond between the fiber and the particles. Importantly, the modification process did not have any adverse effects on the fiber structure. The study further investigated the ballistic performance and protection mechanism of the modified fabrics through mechanical performance tests and ballistic impact tests. The yarn pull‐out experiment revealed that the MPs‐AF composite material exhibited a significant increase in pull‐out force, with a remarkable improvement of 175.6% compared to AF fabric. In the ballistic impact experiments, the MPs‐AF composite material demonstrated a substantial increase in ballistic limit velocity, rising from 52 to 118 m/s when compared to the AF fabric. These findings highlight the potential application of the MPs‐AF composite material in the field of wearable protection. Highlights: Fiber surface modification grafting reaction.A simple and novel solution impregnation method was used to prepare modified AF.Preparation of microcapsule particles by interfacial polymerization.Green new fiber bulletproof material.Chemical grafting produces strong chemical bonds to increase interfacial resistance. [ABSTRACT FROM AUTHOR]

Highlights In this research, the effects of ultimate strain rate and environmental temperature on the mechanical performance of the aramid fiber bundles were experimentally investigated. The scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to detect the tensile failure mechanism of the aramid fiber bundle. The results indicated that the tensile strength, failure strain, elastic modulus, and toughness of the aramid fiber bundle were sensitive to the strain rate, which was represented as the typical bilinear monotonic relationships. In contrast, the impact of environmental temperature on the four parameters of aramid fiber bundle was more complex. The ultimate strength, failure strain and toughness of aramid fiber bundle increased with the temperature changing from −60 to 30°C, but rapidly decreased from 30 to 90°C. Finally, the dispersion of the mechanical performance was quantitatively analyzed based on the scale and shape parameters obtained from Weibull model. Tensile tests for aramid fiber bundle under different strain rates and temperatures were conducted. Strain rate and temperature effects on tensile properties of fiber bundle were quantified. Tensile failure mechanism of fiber bundle was analyzed. Dispersion of the mechanical performance was quantitatively analyzed. [ABSTRACT FROM AUTHOR]

This article presents a new method for synthesizing 2,4-disubstituted oxazoles, which are important compounds with pharmaceutical and therapeutic activities. The authors describe a simple and efficient procedure using readily available materials and a copper catalyst. They successfully synthesized oxazoles with different functional groups in moderate to good yields. The method has potential applications in drug synthesis and ligand synthesis. [Extracted from the article]

In this study, aramid fiber (AF)/phenolic resin prepreg was fabricated by impregnating low content carbon nanotube (CNT)‐reinforced phenolic resin with aramid fabric through a two‐roll pressing process. Both non‐functionalized and carboxylic‐functionalized CNTs (CNTs and CNTs‐COOH) were used for comparison study. For each of the formulations, composite laminate was made by a hot‐pressing process with a number of the prepregs stacked together. Mechanical properties and ballistic performance of the laminates and material failure mechanisms were evaluated and analyzed. Both non‐functionalized and CNTs‐COOH can effectively improve the mechanical and ballistic performance of the laminates. With CNTs‐COOH reinforcement, better results were achieved. As compared with the laminate without CNT reinforcement, 1.0 wt% CNTs‐COOH‐reinforced laminate showed 19.41%, 22.29%, and 45.83% improvement in tensile, flexural, and adhesion shear strength, respectively. The ballistic test results showed that the V50 and the specific energy absorption (SEA) were increased by 5.77% and 13.44%, respectively. The correlation between mechanical and ballistic performance of the composites was analyzed and conducted. [ABSTRACT FROM AUTHOR]

Braking systems are extremely important in any vehicle. They convert the kinetic energy of motion into thermal energy that is dissipated into the atmosphere. Different vehicle groups have different nominal and maximum speeds and masses, so the amount of thermal energy that needs to be absorbed by the friction pads and then dissipated can vary significantly. Conventional friction materials are composite materials capable of withstanding high temperatures (in the order of 500–600 °C) and high mechanical loads resulting from braking intensity and vehicle weight. In small vehicles traveling at low speeds, where both the amount of thermal energy and its density are limited, the use of slightly weaker friction materials with better ecological properties can be considered. This work proposes a prototype composite friction material using flax fibers as reinforcement instead of the commonly used aramid. A number of samples were prepared and subjected to laboratory tests. The samples were prepared using components of plant origin, specifically flax fibers. This component acted as reinforcement in the composite friction material, replacing aramid commonly used for this purpose. The main tribological characteristics were determined, such as the values of the coefficients of friction and the coefficients of abrasive wear rate. For this purpose, an authorial method using ball-cratering contact was used. The results were analyzed using statistical methods. It was found that the composite material using flax fibers does not differ significantly in its tribological properties from conventional solutions; so, it can be assumed that it can be used in the vehicle's braking system. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the impact behavior of fabric laminates composed of carbon, Kevlar, and hybrid materials through low‐velocity impact tests. Non‐hybrid and hybrid laminates were created using layup techniques with sandwich stacking sequences. Drop weight impact tests were conducted using varying levels of impact energy to assess the influence of stacking sequence and hybridization on impact properties. The results showed significant improvements in impact properties with increasing stacking sequence, particularly a 108.8% and 137.4% enhancement in C4 and K4 laminates, respectively. Kevlar laminates exhibited higher energy resistance than carbon laminates, and the Kevlar‐carbon‐Kevlar‐carbon hybrid laminate demonstrated superior impact force and energy absorption capabilities. Additionally, the study analyzed penetration depth and identified different failure modes dependent on stacking sequence and impact energy levels. These findings provide valuable insights for optimizing fabric laminated composites. Thus, the research could be implemented in industries requiring materials with enhanced impact resistance, such as aerospace, automotive, sports equipment, and protective gear manufacturing. Highlights: Investigated the impact performance of stacked fabric structures, including carbon, Kevlar, and hybrid laminated composites, through low‐velocity impact tests.Fabricated both non‐hybrid and hybrid laminates using layup techniques with a sandwich stacking sequence to assess the impact properties of the composite laminates.Observed greater penetration depth in the C2 stacked structure, while the KCKC hybrid laminate showcased greater resistance to a depth of penetration (DOP).Various failure modes were investigated, demonstrating their relationship with stacking sequence and impact energy levels. [ABSTRACT FROM AUTHOR]

The paper presents a study on composites based on 50:50 (PP:LLPE‐g‐MA) reinforced with 0.5, 1, and 2 wt% aramid fibers unmodified/modified with TiO2, processed by melt compounding. Micronic aramid fibers were acetone washed to remove impurities and treated with Ti(IV)isopropoxide precursor via sol–gel method, adding microcellulose for TiO2 particle dimension control. Composites were hot‐pressed into 4 mm‐thick plates for sampling and 0.5 mm‐thick sheets for thermoforming. All composites were successfully thermoformed, fibers‐based samples showing improved thermoforming ability without wrinkling. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive X‐ray spectroscopy (EDS) analysis confirmed the formation of TiO2 particles on the fiber surface. Optical microscopy, SEM and FTIR analysis exhibit the fibers' strong embedment into the matrix due to physical interlocking, generating surface defect reduction. Water absorption decreased from 0.195% (control) to 0.075 and 0% for 1 TiO2 and 2 TiO2 samples, due to material compactization. Contact angles increased from 95.18° (Control) to 108° (1 TiO2) and 112.89° (2 TiO2). The highest flexural strength and modulus were exhibited by 1 TiO2 sample that increased by 44.88% and 47.6% compared to the control sample, due to higher intrinsic rigidity of fibers and TiO2 modifying surface rugosity and phase interaction. The impact strength of the control sample improved by 139% compared to PP due to brittleness reduction, 1 TiO2 by 209% compared to PP, 29% compared to the control sample. The results and excellent thermoformability recommend the materials for encapsulation of electronic/expensive parts in automotive or drone applications, offering viable, facile, rapid, and cost‐effective solutions to easily replace damaged parts. Highlights: Aramid fibers were successfully modified using isopropoxide precursor;Strong embedment of fibers in the polymer diminishes crack propagation/damage;Improved impact and bending properties and water contact angle;The composites showed a high ability to thermoform into complex shapes;Potential to replace non‐reusable materials as encapsulation solutions. [ABSTRACT FROM AUTHOR]

This investigation highlights the performance of high‐performance polymeric composite for ballistic application. Therefore, reinforcement of para‐aramid fiber in poly‐ether‐ketone‐ketone (PEKK) resin film has been made. The surface of PEKK and para‐aramid fiber was modified by low‐pressure plasma to enhance the surface energy of the polymeric film and reinforcement fiber. The polymeric composite was manufactured by compression molding with a pressure of 2 bar, temperature of 310°C with holding time of 15 min. Due to low‐pressure plasma treatment of PEKK film and para‐aramid fiber, the tensile strength of the composites increases considerably. In the accelerated aging test, the tensile specimens are dipped into concentrated HNO3 and NaOH medium for 15 days. It is observed that there is a decrease in tensile strength. The ultimate tensile strength (UTS) of the virgin specimen was compared to the environmentally aged for 15 days and in this case, also there was a decrease in tensile strength. Two types of composite panels were made (i) 25 layers of PEKK film with 24 layers of para‐aramid fabric and (ii) 45 layers of PEKK film with 44 layers of para‐aramid fabric with 15 mm × 15 mm. The composite panel was tested with four 9 mm handgun bullets fired from a distance of 5 meters with a speed of 430 m/s. In the case of 25 layers of PEKK film with 24 layers of para‐aramid fabric, the composite failed under ballistic test, however, in the case of 45 layers of PEKK film with 44 layers of para‐aramid fabric, the composite was successful under ballistic test. Highlights: Film stacking method of PEKK and Aramid fiber.Ballistic composite panel with layers of PEKK and Aramid fiber.Enhancement of mechanical properties of the composite panel with plasma surface treatment.Ballistic testing of composite panel. [ABSTRACT FROM AUTHOR]

Today, aramid fibers are well known as a high‐performance and ideal material for reinforcement purposes in rubber product manufacturing including hoses, tires, cables, and conveyors composites. However, surface modification of aramid fiber is necessary to solve poor interfacial adhesion between aramid fibers and the rubber matrix. Accordingly, in the present study, the effect of the surface modification of aramid fibers using atmospheric pressure plasma treatment with different precursors on adhesion to the rubber matrix was investigated. For that, the plasma coating was conducted using argon as the main working gas, and toluene, acetonitrile, tetraethyl orthosilicate (TEOS), and hexamethyldisiloxane (HMDSO) as liquid precursors. The physical–chemical characterization of the layer confirmed the successful deposition of amorphous carbon, amorphous nitride‐carbon, SiO2, and Polydimethylsiloxane (PDMS)‐like coating layers on the surface of aramid fibers by using toluene, acetonitrile, TEOS, and HMDSO as precursors, respectively. Overall, the result showed that the plasma surface modifications with acetonitrile precursor leads to the increase in interfacial adhesion of aramid/rubber composite, while retaining the tensile strength, and flame resistance properties of aramid as original fibers. Notably, the results of this study confirm the potential use of atmospheric pressure plasma for surface modification of aramid yarn to produce functional aramid for use in rubber composites. Highlights: The plasma‐coated aramid using HMDSO, TEOS, toluene, and acetonitrile precursors was prepared; and its effect on the tensile properties of aramid fiber as well as interfacial adhesion between aramid/rubber composite was investigated.The positive effect of atmospheric pressure plasma coating using HMDSO precursor on the tensile properties of aramid fiber was revealed.The positive effect of atmospheric pressure plasma coating using toluene and acetonitrile on the interfacial adhesion between aramid/rubber composite was revealed.The positive effect of atmospheric pressure plasma coating using TEOS precursor on the flam resistance property of aramid fiber was revealed.This study provides valuable insights into the effect of the different plasma‐coated organosilicon and hydrocarbon precursors on the interfacial adhesion between aramid/rubber composite. [ABSTRACT FROM AUTHOR]

The article explores the use of the enzyme PestE from Pyrobaculum calidifontis VA1 for the enzymatic synthesis of hydroxycinnamic acid amides (HCAAs). HCAAs are natural compounds with potential applications in various industries. The current methods for synthesizing HCAAs are not environmentally friendly, so enzymatic methods are being explored as a greener alternative. The study focuses on the synthesis of N-trans-feruloyltyramine using PestE and found that the reaction was most efficient at 60 °C with a specific molar ratio. The use of acetonitrile as a cosolvent posed challenges, but ascorbic acid could be added to prevent substrate oxidation. PestE was also found to catalyze the formation of other hydroxycinnamic acid amides. Overall, this enzymatic method offers a more sustainable approach to HCAA synthesis. [Extracted from the article]

This article discusses a new method for synthesizing gem-difluoroalkenes, which are compounds that can enhance the bioactivity of drug candidates. The method involves using photoredox catalysis and bromine radicals to directly difluoroallylate certain bonds in amides. The authors optimized the reaction conditions and successfully applied the method to various amides. The article also provides detailed information on the synthesis and characterization of several compounds, including their physical properties and spectroscopic data. This information can be valuable for researchers studying these compounds or related topics. The supporting information for the article is available online. [Extracted from the article]

Membranes are important in the pharmaceutical industry for the separation of antibiotics and salts. However, its widespread adoption has been hindered by limited control of the membrane microstructure (pore architecture and free‐volume elements), separation threshold, scalability, and operational stability. In this study, 4,4′,4′′,4′′′‐methanetetrayltetrakis(benzene‐1,2‐diamine) (MTLB) as prepared as a molecular building block for fabricating thin‐film composite membranes (TFCMs) via interfacial polymerization. The relatively large molecular size and rigid molecular structure of MTLB, along with its non‐coplanar and distorted conformation, produced thin and defect‐free selective layers (~27 nm) with ideal microporosities for antibiotic desalination. These structural advantages yielded an unprecedented high performance with a water permeance of 45.2 L m−2 h−1 bar−1 and efficient antibiotic desalination (NaCl/adriamycin selectivity of 422). We demonstrated the feasibility of the industrial scaling of the membrane into a spiral‐wound module (with an effective area of 2.0 m2). This module exhibited long‐term stability and performance that surpassed those of state‐of‐the‐art membranes used for antibiotic desalination. This study provides a scientific reference for the development of high‐performance TFCMs for water purification and desalination in the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

This study presents an investigation on the mechanical properties and failure mechanisms of composites made of plain woven fabrics reinforced with carbon fibers, aramid fibers, and their intralayer hybrids. The specimens were fabricated by hand lay-up method. Tension, compression, and shear tests were performed in accordance with the relevant standards to investigate the tensile, compression, and shear properties of carbon fiber, aramid fiber, and carbon/aramid fiber intralayer hybrid plain woven composites. Accurate strain field was obtained by digital image correlation (DIC) technology and compared with the results measured by the strain rosettes. Furthermore, a multi-scale modeling strategy was developed to predict the mechanical properties of the hybrid composites. The fiber monofilament model was used to calculate the effective properties of carbon and aramid yarns at the micro-scale level. Representative volume element (RVE) models of the hybrid composite were constructed considering the real fabric pattern at the meso-scale level. The predicted results agree well with the experimental data which validates the multi-scale modeling strategy. The presented information on the tensile, compressive, and shear properties and finite element simulation method of carbon/aramid intralayer hybrid composites should be useful in subsequent research as well as in designing new high-performance composites and structures. [ABSTRACT FROM AUTHOR]

In general, the majority of fiber-reinforced polymer composites (FRPs) used in structural applications comprise carbon, glass, and aramid fibers reinforced with epoxy resin, with the occasional utilization of polyester and vinyl ester resins. This study aims to assess the feasibility of utilizing recyclable and sustainable materials to create a resilient composite suitable for structural applications, particularly in scenarios involving low-velocity and high-velocity impact (LVI, HVI) loading. The paper presents a comparative analysis of the performance of E-glass, aramid, and eco-friendly basalt-reinforcing fabrics as reinforcement fibers in both thermosetting (epoxy) and recyclable thermoplastic (Elium©) resins. Given the limited research on Elium composites, especially those incorporating basalt-reinforcing fiber, there is an urgent need to expand the databases of fundamental mechanical properties for these diverse composites. This necessity is exacerbated by the scarcity of the literature regarding their performance under low- and high-velocity impact loadings. The results of this study will demonstrate the potential of basalt-reinforced Elium composite as an effective recyclable and environmentally friendly structural material system for both static and dynamic loading conditions. [ABSTRACT FROM AUTHOR]

The addition of fibers to asphalt mixtures has the potential to improve the resistance of asphalt mixtures to cracking and permanent deformation (rutting). However, the state (distribution) of fibers in the asphalt mix is critical parameter in determining performance enhancement. This study evaluated the impact of different laboratory mixing methods (mainly Hobart and bucket) on fiber distribution and selected a method comparable to plant-produced fiber-reinforced mixes. The laboratory performance of plant-mixed lab-compacted (PMLC) and lab-mixed lab-compacted (LMLC) fiber-reinforced mixtures was compared. Four types of laboratory and plant mixtures [unreinforced, polyolefin and aramid (PFA) fibers at 0.05% dosage, and Sasobit-coated aramid (SCA) fibers at 0.01% and 0.02% dosages] were produced to compare the laboratory performance of asphalt mixtures. The cracking resistance [evaluated using indirect tensile strength (ITS) and semicircular bend (SCB) tests], rutting susceptibility [evaluated using flow number (FN) and the Hamburg wheel tracking test (HWTT)], durability (evaluated using Cantabro loss), and fatigue (evaluated using a uniaxial fatigue test) performance of control and fiber-reinforced asphalt mixtures were evaluated. Among laboratory mixing methods, a bucket mixer was selected to produce LMLC samples because it produced the maximum fiber distribution (87% of fibers in the individual state). Laboratory performance testing results showed that PFA-reinforced mixtures enhanced the rutting performance regardless of mixing method. The mixtures with PFA 0.05% and SCA 0.01% fibers were highly durable and had better dynamic modulus (|E*|) at low frequency and high temperature. Cracking performance was improved with the addition of SCA fibers into the mix; however, fiber-reinforced mixes (PFA 0.05% and SCA 0.01%) had higher fatigue damage tolerance, except SCA 0.02% reinforced mix. The laboratory bucket mixing method is representative of plant-produced fiber-reinforced mixtures, and laboratory performance results were consistent for laboratory bucket and plant produced mixtures. This paper showcases laboratory mixing method equivalent to fiber distribution that produce fiber-reinforced asphalt mixtures comparable to those produced at an asphalt plant. Different laboratory mixing equipment, including Hobart and bucket mixers, was used to produce fiber-reinforced asphalt mixtures in the laboratory. Aramid fibers were added into these mixers after separation by hand. In addition, the same fiber-reinforced mixtures were produced at a batch plant for comparison purpose. Fibers and binder were extracted from all mixtures and individual fibers (indicating better fiber distribution) were quantified. According to the results, the use of a bucket mixer led to better fiber distribution within the produced asphalt mixtures than did a Hobart mixer. Laboratory performance comparison results showed that the mixes produced using the bucket mixer had identical results to plant-produced mixtures. Hence, using a bucket mixer and introducing aramid fibers after hand separation is an effective way to produce plant-representative fiber-reinforced asphalt mixtures. This is a major step toward designing and producing fiber-reinforced asphalt mixtures and enhancing the cracking performance of asphalt mixtures. [ABSTRACT FROM AUTHOR]

Particle‐reinforced polymer composites have figured prominently in technological appliances owing to their high mechanical modulus and strength. Due to the obvious demand for lighter but more resilient composites to substitute heavy metal parts, several investigations have been made into particle‐based composites. The current research investigates the impact of reinforcing aramid fiber (PPTA), glass wool (GW), aluminum (Al), and silicon carbide (SiC) powder into an epoxy matrix on aspects of mechanical and morphological characteristics. Hand lay‐up technology was performed to manufacture composites at five different degrees of reinforcement loading (5, 10, 20, 30, and 40 wt. %). SEM and optical microscopes were used for microstructural investigation in order to evaluate the cohesion and dispersion of the reinforcing particles across the matrix phase of the hybrid composites. The elongation at break, flexural strength, flexural modulus, and hardness of epoxy‐PPTA‐GW−Al‐SiC hybrid composites improved, whereas the tensile strength and impact strength decreased from 5 wt. % to 40 wt. % loading. Among fabricated hybrid composite compositions, the morphological and mechanical characteristics obtained at 40 wt. % PPTA, GW, Al, and SiC powder loading are the best among all others. [ABSTRACT FROM AUTHOR]

A series of seven stable amide derivatives based on indole‐3‐carboxaldehyde were synthesized with high yields using various aliphatic and aromatic acyl chlorides, triethylamine and DMAP as the catalyst at room temperature. Structural characterization was performed using FT‐IR, 1 H‐NMR, 13C‐NMR and LC–MS techniques. To develop bioactive material, acetalization of water‐soluble polyvinyl alcohol was achieved by reacting one of the N‐acyl derivatives, 1‐propionylindole‐3‐carboxaldehyde, in the presence of a p‐TSA catalyst to form polyvinyl acetal with pendant bioactive groups. The polymer was analyzed using 1 H‐NMR, FT‐IR, TGA, DSC, FE‐SEM and EDX spectroscopic techniques. The polymer was water‐insoluble with enhanced thermal stability compared to pure polyvinyl alcohol. This approach for developing N‐acyl derivatives of indole‐3‐carboxaldehyde and then reacting one of the monomers with polyvinyl alcohol to improve its thermal properties and stability in humid conditions has proven successful. [ABSTRACT FROM AUTHOR]

An experimental design method is proposed to guide the selection of specimen dimension and split Hopkinson pressure bar apparatus. This method is applicable to the woven composite with modulus independent of strain rate. This method can predict the maximum specimen dimension at the desired strain rate under the maximum strike velocity of the apparatus. Based on the proposed design method, the in‐plane dynamic compressive behavior of 2D plain weave carbon/aramid hybrid composite was obtained. The strength exhibited sensitive to strain rates. The nonlinear constitutive model described the dynamic constitutive relationship effectively. The distribution of delamination failure significantly influenced the final failure shape of the specimens through the high‐velocity camera. Microscopic observations indicated that carbon fiber yarns and aramid fiber yarns exhibited different fracture modes. Highlights: An experimental design method applicable to woven composites in dynamic tests.Negative correlation between strength and strain rate of hybrid composites.The validity of the nonlinear constitutive model to dynamic property.The effect of hybridization and strain rates on damage modes. [ABSTRACT FROM AUTHOR]

The finite element model of a 7.62 mm armor‐piercing incendiary bomb penetrating lightweight composite target is established. The structure of the target plate is composed of boron carbide ceramic/carbon fiber laminate/aramid fiber laminate/damping material. The reasonable distribution position of damping material is explored by designing the material structure and geometric parameters. Genetic algorithm is used to optimize the structure of the lightweight composite target plate, and the feasibility of the optimization results is verified through experiments. The results show that under the same surface density, the energy absorption value of the target plate with a certain thickness of back layer damping is 1.36% higher than that of the target plate without damping. And the damping material on the back layer can act as a buffer layer to reduce blunt trauma caused by bullets to the human body. The surface density of the optimized lightweight composite target plate is reduced by 21.6% under the same protection capability. This work provides a theoretical foundation for the impact resistance design and optimization of lightweight composite target plates. Highlights: Impact resistance performance of lightweight composite target plate is investigated.The impacting analytical model of the structure is established.The validity of the optimized impacting analytical model is verified by numerical simulation. [ABSTRACT FROM AUTHOR]

The coating was created on the surface of aramid fibers (AFs) by solution dip‐coating and in situ UV curable method, using a polymerizable deep eutectic solvent (PDES), dissolved poly(ethylene imine), and poly(ethylene glycol) diacrylate (PEGDA). Fourier transform infrared spectroscopy and thermogravimetry confirmed the successful construction of the coating on the AF surface, which accounted for 12%–17% of the total fiber mass. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed a 2 μm increase in fiber diameter and a maximum fiber surface average roughness (Ra) of 263.7 nm when the polyethyleneimine content was 0.5% (AF‐PDES‐0.5). Based on these results, H pull‐out samples of fiber/rubber composites were fabricated. The results indicated that the H pull‐out force of AF‐PDES‐0.5 samples increased by 109.74% than that of untreated fiber, and reached 12.92 N of the maximum strength. In summary, the method is simple, rapid, non‐polluting, capable of continuous, and intelligent construction of coatings on the surface of AF. Thus, making it highly promising for application in the field of aviation tires. Highlights: Using PDES, green, and low‐carbon preparation processes.Solution dip‐coating and UV reaction for improved reaction speed and workability.Quantitative of interface thickness and modulus using EDS and AFM. [ABSTRACT FROM AUTHOR]

This article explores the synthesis and characterization of furan-based polyamides using a continuous flow system. The researchers successfully synthesized the polyamides without impurities and optimized the synthesis process by adjusting reaction conditions. The resulting polyamides exhibited amorphous characteristics and thermal stability comparable to petroleum-based polyamides. The authors also demonstrated the depolymerization of the polyamides back into their monomers using acid-catalyzed hydrolysis, suggesting that this approach has potential for industrial applications and offers a sustainable alternative to fossil-based polyamides. [Extracted from the article]

The document is the contents list for the journal "Chemical Communications" published on May 7, 2024. It includes a feature article on the chemistry of gold( I)– ethylene complexes, as well as several communications on various topics such as catalysis, organic synthesis, and electrochemistry. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document provides a list of articles and authors, along with images and permissions for reproduction. [Extracted from the article]

Herein, we demonstrated a visible light mediated tandem oxidation–organo catalyzed C−S bond functionalization protocol for the cleavage of aromatic C−S bond. The investigation encompassed the functionalization of C−S bonds within sulfones, sulfoxides, and aliphatic sulfide derivatives. However, the process of functionalizing the C−S bond in aromatic sulfides remains uncertain. The presented protocol demonstrates the C−S bond functionalization on benzo[b]benzo[4,5]thieno[2,3‐d]thiophene derivative and amines including primary and secondary amines as well. A radical mediated mechanism was proposed for the tandem oxidation–organocatalyzed C−S bond functionalization protocol. [ABSTRACT FROM AUTHOR]

The article discusses a method for synthesizing amide bonds using deoxyfluorinated carboxylic acids and pyridinesulfonyl fluoride. The authors optimized the reaction conditions and explored the substrate scope, demonstrating the versatility and utility of their method. They also showcase the application of this methodology in the synthesis of a challenging ester-linked compound and a tetrapeptide. The research was supported by various funding sources, and there are no conflicts of interest to declare. This article provides valuable information for researchers in the field of medicinal chemistry and organic synthesis. [Extracted from the article]

The Applications of silica aerogel are limited due to its brittleness and low strength. As a result, it is essential to strengthen and toughen it. Organic nanofibers are one of the preferred reinforcement materials. In this work, we designed and fabricated flexible and compressible nanostructure-assembled aramid nanofiber/silica composites aerogel (ANF/SiO2 aerogel) to improve the mechanical strength and flexibility of silica aerogel without compromising thermal insulation properties. The aramid nanofiber/silica composite aerogels were prepared by immersing the aramid nanofiber wet gel into the silica sol for a certain period of time followed by freeze drying without solvent replacement. The surface modifier 3-aminopropyltriethoxysilane (APTES) was used as a coupling agent to form chemical linkage between the ANF fiber and silica gel. It was observed that APTES can effectively drive the silica sol to infuse into ANF hydrogel, promoting the assembly of silica gel onto the fiber surface and a uniform distribution in the network of ANF. The compressive resilience, thermal stability, and thermal insulation properties of the composite aerogels were evaluated by inducing the silica aerogel into the ANF network to form a protective layer on the fiber and change the pore structure in the ANF network. [ABSTRACT FROM AUTHOR]

Multi-layer ceramic/fiber reinforced polymer (FRP) composite, especially Al2O3/carbon-aramid hybrid FRP composite, is a common ceramic composite armor system (CCAS) in the protection field. Aiming at selecting an optimal configuration from several schemes with different discrete structural parameters, including the thickness ratio of carbon fiber (CF) to aramid fiber (AF), the prepreg's number of layers (PNL) of CF and AF, etc., a two-step comprehensive optimization and evaluation method is proposed based on the parametrical study of the ballistic behavior and improved analytical hierarchy process (AHP) conducted by finite element analysis (FEA) and Python programming, respectively. The results demonstrate the effectiveness of this two-step methodology despite the influence of these discrete factors on the ballistic behavior is intricate. Besides, when the PNL is less, the configuration with the PNL of CF is 8, the thickness ratio of CF to AF is 3:7 and the PNL of AF is 14 is the desirable design scheme with the highest comprehensive ballistic behavior. [ABSTRACT FROM AUTHOR]

We performed direct carbamoylation using heteropoly acid (HPA) photocatalysts with a Keggin structure under UV‐light. Carbamoyl radicals were generated via the decarboxylation of N,N‐disubstituted dimethyloxamic acid under these conditions. The HPA catalyst functioned as a photocatalyst when the dicarbonyl bond was broken, generating carbon dioxide. We found that disubstituted carbamoyl radicals readily coupled with aromatic bromides to generate diverse benzoic amides. In particular, using a homogeneous HPA photocatalyst improved the reaction's transmittance, which had been a problem of the existing heterogeneous photocatalyst. This reaction condition can be easily handled, mild, and safer than the traditional benzoic amide synthesis. This method can be scaled up efficiently, is eco‐friendly, and can be applied to producing active pharmaceutical ingredients. [ABSTRACT FROM AUTHOR]

As phenanthroline (phen) possesses great coordination ability with various ions, the development of new chiral phen ligands is in great demand in asymmetric catalysis. Herein, we rationally designed and developed an entirely new class of C2-symmetric rigid-featured chiral phen ligands that provide the N,N,O,O-tetradentate coordination of the phen moiety and two additional N,N-dioxides. The chiral ligands, termed Phen-2NO ligands, incorporate the advantages of both the phen skeleton and the pyrroloimidazolone-based N-oxide moiety, and their electronic and steric properties can be readily tuned through the incorporation of substituents in the aromatic rings of the amide group. These ligands presented a superior performance in the Ni(II)-catalyzed asymmetric Michael-type Friedel–Crafts alkylation reaction of indoles with β,γ-unsaturated α-ketoesters. Excellent yields (up to 93%) and high enantioselectivities (up to 99% ee) are obtained for a wide range of substrates under mild conditions. These results demonstrated the promising potential of the Phen-2NO ligand as an efficient chiral phen ligand. [ABSTRACT FROM AUTHOR]

Heterocyclic aramid fibers (HAFs) with high strength and high modulus are widely used in the field of impact resistance. However, the weak interaction between molecular chains of HAFs seriously hinders the simultaneous improvement of strength and modulus. Herein, small addition (0.05 wt%) of nanosized acyl‐chloride‐activated graphene whiskers (NGW‐Cl) is used as reinforcements to simultaneously increase the strength and modulus of HAFs. The resultant NGW‐Cl/HAFs monofilament displays high tensile strength and modulus of 6.31 and 152 GPa, which are 19% and 18.8% higher than that of HAFs. The NGW‐Cl/HAFs multifilaments show high tensile strength and modulus of 36.16 and 1008 cN per dtex, which are 19.34% and 24.14% higher than that of HAFs. Especially, the dynamic modulus of NGW‐Cl/HAFs is up to 268.0 GPa at 200 HZ, which is increased by 92.8% compared with HAFs (139.0 GPa), showing a great application potential in high‐frequency vibration fields. Additionally, the strength and modulus of NGW‐Cl/HAFs impregnated multifilaments is up to 6.08 and 152 GPa, which is increased by 24.5% and 28.8% compared with HAFs. This apparent improvement is because the strong chemical bonding between NGW‐Cl and heterocyclic aromatic chains enhances heterocyclic aromatic chain interaction, inducing high crystallinity and orientation of HAFs. [ABSTRACT FROM AUTHOR]

Tetraglycidyl diamino diphenyl methane (TGDDM) and its carbon fiber composite are widely studied and used because of their heat resistance and high performance. In order to obtain efficient reinforcing effects in a simple manner, we adopt the idea of molecular composite—uniformly dispersing the rigid‐rod macromolecules in the TGDDM matrix. Herein, we prepared fully aminated‐poly(p‐phenylene terephthalamide) by direct polycondensation and hydrogenation reduction as the reinforcing agent. The fully aminated‐PPTA is distributed uniformly in the cross‐linked epoxy resin (EP) network by chemical bonds, and achieves efficient reinforcement. With the addition of only 0.5 wt% fully aminated‐PPTA, the tensile strength and Young's modulus of EP are improved to 127.7 ± 7.4 MPa (+28%) and 3.36 ± 0.15 GPa (+44%); the flexural strength and modulus are improved to 209.6 ± 9.4 MPa (+42%) and 3.70 ± 0.14 GPa (+37%); the notch impact strength is improved by 32%. Crucially, the heat resistance of EP almost remains unchanged. Furthermore, the flexural properties and interlaminar shear strength of the carbon fiber composite are also comprehensively increased. Compared with other modified fillers, the fully aminated‐PPTA is simple to prepare and blend, and is an efficient reinforcing agent for TGDDM and its carbon fiber composite benefitting from its rigid‐rod main chain and amino side groups. Highlights: Molecular composite can achieve excellent strengthen and toughen effects.Fully aminated‐PPTA is embedded uniformly in EP network by chemical bonds.TGDDM is effectively reinforced without deteriorated heat resistance.Fully aminated‐PPTA is also a comprehensive reinforcement for EP/CF composite. [ABSTRACT FROM AUTHOR]

Fires constitute a significant threat due to the pollutants emitted and the destruction they cause. People who take part in firefighting operations must be equipped with appropriate tools, including special clothing that will allow them to work and guarantee safety. One of the threats is represented by compounds from the PAH (Polycyclic Aromatic Hydrocarbons) group, which are characterized by high toxicity and carcinogenicity. Therefore, it is important that the materials used constitute a barrier to contamination. Various materials from which individual elements of special firefighter's clothing are made were tested. Additionally, the effect of height on the possibility of sorption of PAH compounds on a given type of material was analyzed. Based on the obtained analysis results, it was found that both the type of material and the zone in which the clothing items are used are important in the sorption processes of pollutants. For example, PAHs with high molecular weight are most likely to settle on rubber, i.e., the material from which shoes are made, with the exception of Chrysene, whose presence was found primarily in aramid fibers, i.e., the material from which trousers and jackets are made. However, among PAHs with low molecular weight, compounds such as Methylnaphthalene,1- and Fluorene were sorbed on the rubber surface in large quantities. The only compound that is present in comparable amounts in all materials is Acenaphthylene. Data in this area may be important for taking further actions related to the modification of materials used in special fire brigade clothing and in their cleaning processes. [ABSTRACT FROM AUTHOR]

The mechanical recycling of discarded plastic products as resources for environmental preservation has recently gained research attention. In this context, it is necessary to use waste materials for fiber-reinforced thermoplastics (FRTP). Glass and carbon fibers are often damaged by shear and compression during melt-forming processes. To achieve a sustainable society, it is necessary for thermal recycling to produce minimal to no residue and for mechanical recycling to maintain the length of fibers used in FRTP to preserve their performance as a reinforcing agent. Aramid fibers (AFs) do not shorten during the melt-molding process, and their composites have excellent impact strength. On the other hand, plastics reinforced with glass or carbon fibers are reported to have a superior strength and modulus of elasticity compared to aramid fibers. This study investigates the dispersion of a carbon nanofiber (CNF), a whisker, as the third component in aramid-fiber-reinforced polypropylene (PP/AF). The results and discussion sections demonstrate how the dispersion of CNF in PP/AF can enhance the mechanical properties of injection-molded products without compromising their impact resistance. The proposed composition will have excellent material recyclability and initial mechanical properties compared to glass-fiber-reinforced thermoplastics. [ABSTRACT FROM AUTHOR]

This study presents the effect caused by the saline environment (artificial seawater) on the physical and tribological properties of laminated composite materials reinforced with aramid fibers when they are subjected to erosive wear by sand particles. Composite materials made by epoxy resin and reinforced with glass fiber, carbon fiber and hybrid fiber (aramid with carbon) were studied. The laminates were superficially reinforced with layers of Kevlar fiber and prepared by the vacuum-assisted resin infusion process. The samples were subjected to a seawater accelerated aging process at 70°C for 1122 h. To reproduce erosive wear conditions of marine structural components, sea sand was used as solid particle under conditions of 4.5 bar of pressure, impact speed of 4.7 m/s and impact angle of 90°. The results showed that aged materials absorb more impact energy with respect to unaged counterparts, causing less material loss and a less depth in the wear track. The information generated by this research work may serve for the design and durability analysis of marine structures such as tidal turbine blades. [ABSTRACT FROM AUTHOR]

In this study, ablative resistance of single fiber‐ and hybrid fiber‐reinforced epoxy‐modified vinyl silicone rubber (EMVSR) composites was systematically studied. Three types of fibers, namely aramid fiber (AF), basalt fiber (BF), and carbon fiber (CF), were employed as the reinforcements. The results indicated that the incorporation of fiber reinforcements effectively suppressed the expansion and strengthened the char layer. Besides, the quality of char layer was quite different when different types of fibers were used. The char layer of AF‐modified samples had more surface defects, BF‐modified samples were brittle, and CF‐filled samples were dense and flat. The use of hybrid AF/BF fibers improved the ablation and anti‐erosion performance of EMVSR. Meanwhile, the thermal insulation performance was enhanced because the back‐face temperature was the lowest with the addition of 1 phr AF and 5 phr CF. The above results indicated that the ablation and anti‐erosion resistance and the quality of char layer as well as the thermal insulation behavior of EMVSR were significantly improved by incorporating fibrillar fillers, which demonstrate practical applications as flexible anti‐ablation materials for thermal protection systems. Highlights: Epoxy‐modified vinyl silicone rubber was used for preparing ablative composites.The effect of adding different fibers on the ablation properties was studied.The presence of single fibers improved the strength of char layer.The use of hybrid fibers was found effective in enhancing the ablative properties.The intrinsic property and entanglement of fibers affected the ablative properties. [ABSTRACT FROM AUTHOR]

Methanogenic archaea inhabiting anaerobic environments play a crucial role in the global biogeochemical material cycle. The most universal electrogenic reaction of their methane-producing energy metabolism is catalyzed by N 5 -methyl-tetrahydromethanopterin: coenzyme M methyltransferase (MtrABCDEFGH), which couples the vectorial Na+ transport with a methyl transfer between the one-carbon carriers tetrahydromethanopterin and coenzyme M via a vitamin B12 derivative (cobamide) as prosthetic group. We present the 2.08 Å cryo-EM structure of Mtr(ABCDEFG)3 composed of the central Mtr(ABFG)3 stalk symmetrically flanked by three membrane-spanning MtrCDE globes. Tetraether glycolipids visible in the map fill gaps inside the multisubunit complex. Putative coenzyme M and Na+ were identified inside or in a side-pocket of a cytoplasmic cavity formed within MtrCDE. Its bottom marks the gate of the transmembrane pore occluded in the cryo-EM map. By integrating Alphafold2 information, functionally competent MtrA-MtrH and MtrA-MtrCDE subcomplexes could be modeled and thus the methyl-tetrahydromethanopterin demethylation and coenzyme M methylation half-reactions structurally described. Methyl-transfer-driven Na+ transport is proposed to be based on a strong and weak complex between MtrCDE and MtrA carrying vitamin B12, the latter being placed at the entrance of the cytoplasmic MtrCDE cavity. Hypothetically, strongly attached methyl-cob(III)amide (His-on) carrying MtrA induces an inward-facing conformation, Na+ flux into the membrane protein center and finally coenzyme M methylation while the generated loosely attached (or detached) MtrA carrying cob(I)amide (His-off) induces an outward-facing conformation and an extracellular Na+ outflux. Methyl-cob(III)amide (His-on) is regenerated in the distant active site of the methyl-tetrahydromethanopterin binding MtrH implicating a large-scale shuttling movement of the vitamin B12-carrying domain. [ABSTRACT FROM AUTHOR]

The structure of previously unknown condensation products of a series of aldoses (N-acetyl-D-glucosamine, D-mannose, D-galactose, and L-fucose) with 4-mercaptobutyric acid hydrazide, promising glyco-ligands of noble metal nanoparticles, has been studied by means of 1H and 13C NMR spectroscopy. It has been shown that the derivatives of N-acetyl-D-glucosamine, D-mannose, and D-galactose exist as a tautomeric mixture of open hydrazone and cyclic pyranose forms in the solution in DMSO-d6. The linear hydrazone form is represented by a set of Z′,E′-conformational isomers, differing in the arrangement of substituents relative to the amide C–N bond, in comparable quantities. The condensation product obtained from L-fucose is an exclusively cyclic pyranose structure in the crystalline state and in solutions in DMSO-d6, represented by a single β-configuration isomer. [ABSTRACT FROM AUTHOR]

The paper investigates the normal interaction between the steel striker, carbon fiber and aramid fiber reinforced plastic plates at a speed ranging from 166.6 to 184.2 m/s. A series of physical and numerical experiments with impact load is conducted to design a mathematical model and numerical algorithm for the composite plate. The behavior and fracture of composites are described by the elastic-brittle model accounting for their different compressive and tensile strengths. The numerical simulation utilizes the finite element method in the EFES software developed by the authors. [ABSTRACT FROM AUTHOR]

Porous crosslinked aromatic polyamides were prepared in a single-step process by reacting a triacid chloride monomer with a diamine monomer having COOH groups via a precipitation polymerization method. The resulting materials were agglomerates of polyamide particles having COCl and COOH groups with average diameters of 30–70 nm and average pore diameters in the range of ca. 20–40 nm. The concentration of COCl groups and the porous structure were significantly affected by the monomer ratio, the total monomer concentration and the reaction solvent. These COCl groups were subsequently modified by reaction with 1,8-diaminooctane in three different solvents, and the extent of modification depended strongly on the solvent. This modification produced aromatic polyamides having two types of crosslinking, based on of the 1,8-diaminooctane and the aromatic polyamide product, which were cleaved in different temperature ranges. The COCl groups introduced were found to have high reactivity and react with NH2 groups even in water, prior to hydrolysis. [ABSTRACT FROM AUTHOR]

Remarkable advances in the research and development of micro/mini Unmanned Aerial Vehicles (UAVs) seek thin, lightweight and strong materials for their structural applications. As these structures involve various loading conditions in both the in-plane and through-the-thickness directions during their life cycle, the assurance of the structural stability in each direction is deemed mandatory. The woven Aramid fibers as high strain materials (HSM) are known to improve the through-the-thickness impact strength. However, the addition of the HSM can affect the overall tensile behavior of composite laminates. This study investigates the effect of the woven Aramid fiber on the in-plane tensile behavior of Carbon/ epoxy laminates. Laminates are fabricated using an easy and cost-effective Vacuum Assisted Resin Infusion Molding (VARIM) setup. A uniaxial tensile test was conducted to analyze the tensile behavior of Carbon/Aramid hybrid composites. The effect of adding the woven Aramid layer and the Carbon fabric sequence on the tensile modulus, strain to failure and modulus of toughness are investigated in this study. The results revealed that the presence of Aramid has a positive hybrid effect on the failure strain, exhibiting pseudo-ductile behavior with a compromise in the tensile modulus of the virgin Carbon/epoxy laminate. [ABSTRACT FROM AUTHOR]

An imidazolium‐type room‐temperature ionic liquid containing silsesquioxane frameworks is successfully prepared. The polar ionic liquid products are grafted onto the surface of prepared aromatic polyamide (PA) membranes to improve water flux of PA membranes. Membranes grafted with an ionic liquid exhibit a water flux of 1.89 L m−2 h−1 bar−1), 48% higher than that of pure PA membranes while the salt rejection still remains at 96%. This improvement can be attributed to the enhanced hydrophilicity of the membrane surface, as evidenced by the reduced water contact angle. [ABSTRACT FROM AUTHOR]

Currently, fiber-reinforced polymer composites (FRPs) used for demanding structural applications predominantly utilize carbon, glass, and aramid fibers embedded in epoxy resin, albeit occasionally polyester and vinyl ester resins are also used. This study investigates the feasibility of employing recyclable and sustainable materials to formulate a composite suitable for load-bearing structural applications, particularly in scenarios involving low-velocity and high-velocity impacts (LVIs and HVIs, respectively). The paper presents a comparative analysis of the performance of basalt–Elium, a fully recyclable, sustainable, and environmentally friendly composite, with an epoxy-based counterpart. Moreover, an accurate and reliable numerical model has been developed and introduced through which the response of these composites can be examined efficiently and accurately under various loading states. The results of this investigation demonstrate the viability of the basalt–elium composite as a fully recyclable and sustainable material for crafting efficient and lightweight composites. Additionally, the accurately developed finite element model presented here can be used to assess the influence of several parameters on the composite, thereby optimizing it for a given situation. [ABSTRACT FROM AUTHOR]

Herein, we report an asymmetric two-component alkenyl Catellani reaction for the construction of C--N axial chirality through a palladium/chiral norbornene cooperative catalysis and an axial-to-axial chirality transfer process. Various partially aromatic iodinated 2-pyridones, quinolones, coumarin and uracil substrates react with 2,6-disubstituted aryl bromides with a tethered amide group, to afford a wide variety of polycyclic C--N atropisomers (38 examples, up to 97% e.e.). The obtained C--N axial chirality originates from the preformed transient C--C axial chirality with high fidelity. The synthetic utility of this chemistry is demonstrated by facile preparation of complex quinoline and pyridine based C--N atropisomers through a N-deprotection and aromatization sequence. In addition, a remote axial-to-central diastereoinduction process dictated by C--N axial chirality is observed with excellent diastereocontrol. [ABSTRACT FROM AUTHOR]

This study presents a method for predicting the vibrational frequencies of naphthalene (C10H8) using a vibrational Hamiltonian approach that preserves the D2h symmetry of the molecule. The method incorporates linked one-dimensional Morse oscillators to replicate the behaviors of the aromatic C-H and C-C bonds and their interrelated dynamics. The outcomes of this research offer precise predictions for the fourth and fifth overtones, validating the model's effectiveness in reflecting the complex vibrational dynamics of naphthalene. Thus, this work contributes to a deeper comprehension of the vibrational characteristics of naphthalene and establishes a detailed methodological basis for analyzing the vibrational spectra of similar polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

A novel nickel‐catalyzed practical and simple synthesis of thioesters from amides and disulfides has been developed. Diverse substituted aromatic amides are capable of coupling with diaryl or dialkyl disulfides via C−N/S−S bonds cleavage to produce the desirable thioesters in moderate to good yields. This procedure features cheap metals, novel and easily preparative substrates, providing a simple and practical access to a variety of thioesters without toxic thiols or CO gas. [ABSTRACT FROM AUTHOR]

The Ti(OPr‐i)4‐mediated three–component condensation of enantiomeric Ellman's amides, dimethylphosphine oxide, and aliphatic, aromatic or heteroaromatic aldehydes proceeds in high yields and diastereoselectivities enabling the rapid, scalable and general asymmetric synthesis of (α‐amino)dimethylphosphine oxide derived compounds bearing alkyl, cycloalkyl or hetaryl group at the chiral carbon atom. Asymmetric synthesis of α‐amino‐α‐polyfluoroalkyl dimethylphosphine oxides was accomplished through diastereoselective addition of dimethylphosphine oxide to enantiomeric Ellman's aldimines, RFCH=NS(O)tert‐Bu (RF=CF3, CHF2, PhCF2). [ABSTRACT FROM AUTHOR]

In this study, the traditional mini split Hopkinson tension bar (SHTB) was enhanced for the dynamic mechanical performance testing of single fiber/resin interface of composites. Single Aramid III fibers were modified using a polyamine modification treatment. Quasi-static and dynamic tensile tests of modified single Aramid III fibers were conducted using an electronic tensile testing machine and mini SHTB. The test results indicated that the surface modification employing the Catechol-Tetraethylenepentamine (Cat-TEPA) approach had a negligible effect on the tensile mechanical properties of single Aramid III fibers. The microdroplet method was introduced to measure the dynamic interfacial shear strength (IFSS) of Aramid III fiber/waterborne polyurethane resin using a mini SHTB. The dynamic shear test results revealed an increase in the dynamic shear strength of the modified Aramid III fiber/resin interface from 36.16 MPa to 41.51 MPa. Furthermore, the Scanning Electron Microscope (SEM) photography of the modified single Aramid III fiber after debonding exhibited regular grid structures on the debonding area, which can prevent debonding between the single fiber and the microdroplet, thereby enhancing interfacial shear performance. [ABSTRACT FROM AUTHOR]