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Frontal polymerization has great potential in complementing additive manufacturing processes such as direct ink writing as a continuous cure synchronized to the printing speed can overcome issues such as sagging. To study the incorporation of frontal polymerization into a potential printing process, a frontally polymerizable DGEBA epoxy resin has been developed for both UV and thermal initiation. Through frontal polymerization alone, full conversion is observed with a starting glass transition of 150[degrees]C for both initiation methods. Resulting thermal behavior is shown to have little dependence on either initiation irradiance or temperature utilized and much greater dependence on initiator concentration in the resin. Mechanical behavior is maximized by varying initiator concentration and cure conditions achieving tensile stress of 75 MPa and [K.sub.1C] of 1.2 MPa-[m.sup.1/2]. Shelf stability of the resin proves promising with no viscosity change after 12 weeks of room temperature storage. Future studies will concern adapting the resin for both direct ink writing and continuous fiber additive manufacturing applications. Highlights * Frontal polymerization of EPON 826 using RICFP * Utilized a tetrakis borate containing diaryliodonium cationic initiator * Stable and polymerizable after 12 weeks * Resin printed and frontally cured using UV initiation KEYWORDS direct ink writing, epoxy, frontal polymerization, 1 | INTRODUCTION Frontal polymerization has continued to be a promising rapid manufacturing solution in which polymerization propagates in a localized reaction zone. (1) More specifically, a single stimulus initiation [...]

Purpose: This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives. Materials and Methods: Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and μTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or μTBS using a universal testing machine at a crosshead speed of 0.5mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at a = 0.05. Results: Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p<0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group. Conclusion: Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives. [ABSTRACT FROM AUTHOR]

The editor's choice for November 2024 in SPE's Polymer Engineering & Science journal is Anatoly E. Chalykh's article, 'Supramolecular Structure of Epoxy Oligomers.' Recent research by Anatoly E. Chalykh reveals [...]

The cooling time in injection molding is defined as the period during which the molten plastic in the mold solidifies and cools to a temperature suitable for safe ejection without deformities. Efficient cooling is crucial for large-volume production in the plastic injection molding industry. This study investigates the cooling performance of rapid tooling made from aluminum-filled epoxy resin with varying inner cooling channel surface roughness. This study includes creating a microstructure on the cooling channel surface to assess its impact on cooling efficiency. The study produces rapid tooling with both parallel and series cooling channels. The average cooling time for molded wax patterns is lower with parallel cooling channels than serial cooling channels. Nanobubble coolant shortens the cooling time of molded wax patterns based on experiments of low-pressure wax injection molding. The average cooling time-saving ratio is about 15.4% from five low-pressure injection moldings using nanobubble coolant. [ABSTRACT FROM AUTHOR]

In this work, 1–3 connectivity barium zirconate titanate ceramic cement-based composites were fabricated using Portland cement and epoxy resin as the matrix. Barium zirconate titanate (BZT) of 40–60 % by volume was used while epoxy was used with cement at 0–7% by volume. Dielectric and piezoelectric properties, and other properties such as acoustic impedance, density and microstructure were investigated. It was found that epoxy resin can be used in combination with BZT to achieve a suitable acoustic impedance value (9–11 × 106 kg/m·s2) matching that of concrete for structural health monitoring application. Thus, when epoxy resin was used at 7 %, BZT volume can be increased to 60 % where the highest d 33 value of 93 pC/N was found and remain within the acoustic matching range. In addition, when epoxy resin was increased, both piezoelectric charge coefficient (d 33) and piezoelectric voltage coefficient (g 33) were also found to increase. This is likely due to the lower porosity thus denser matrix when epoxy resin was used in addition to cement. [ABSTRACT FROM AUTHOR]

Boron nitride, as an excellent thermal conductive filler, has received widespread attention in the field of heat dissipation, and its interface thermal transport with organic matrix is a key issue for improving thermal conductivity. In this study, several typical modifiers are selected to modify boron nitride to improve its interfacial compatibility with epoxy resin. The composition of functional groups, crystal structure and factors affecting thermal conductivity of the modified boron nitride surface are systematically studied. The influence of main factors such as the structural characteristics of grafted molecules and the grafting functional groups on the construction of thermal conductivity channels was analyzed in detail. The results show that shorter chain length and fewer cross-linked branches are more conducive to phonon transport and propagation. The thermal conductivity of BN-KH570/EP composite at 26 wt% load reaches 1.52 W/m·K, which is 7.6 times that of pure epoxy resin. It also maintains good thermal stability at 600 °C, which provides a new idea for improving the interface interaction of boron nitride composites. [ABSTRACT FROM AUTHOR]

The corrosion problem of metals has caused significant economic losses and safety risks in industrial production. Therefore, it is imperative to take measures to against corrosion. This study develops a new type of hyperbranched epoxy resin for anticorrosive coatings that contain catechol groups similar to mussels. The anticorrosive epoxy coating exhibits extremely high hardness and strength, outstanding thermal stability, excellent adhesion, as well as remarkable resistance to water and salt spray. The results of mechanical test showed that the tensile strength of the coatings could achieve as high as 63 MPa and their pencil hardness reached 8 H. After 30 days of immersion in saltwater, the pencil hardness could still keep 6 H, respectively. Furthermore, compared with the HBEP coating, the PCA-modified coating exposed to salt spray environment for 30 days shows less corrosion on both its surface and scratch area. This new type of coating has tremendous potential applications in areas such as marine metal protection. [ABSTRACT FROM AUTHOR]

This study investigates the impact of zinc oxide nanoparticles on epoxy resin systems and the ultraviolet (UV) aging resistance of modified epoxy resin composites using molecular dynamics (MD) simulations and experimental methods. Initially, various epoxy resin cross‐linking models are established through MD simulations to understand the influence of different nano ZnO contents on resin modification, further validated by experiments. Subsequently, the UV radiation resistance of nano ZnO–epoxy resin composites is assessed by subjecting them to high‐intensity UV radiation equivalent to 3 years of natural environmental conditions, analyzing changes in tensile properties, impact performance, hardness, and glass transition temperature of epoxy resin before and after UV radiation exposure. The findings suggest that the addition of nano zinc oxide reduces the impact of UV radiation on epoxy resin, with optimal UV radiation resistance observed at a nano zinc oxide mass fraction of 0.3 wt%. [ABSTRACT FROM AUTHOR]

Recently, composites have attracted many researchers, which have advanced favored properties compared to metallic materials, such as high strength with lightweight as well as corrosion and erosion resistance and others. However, these resources are exposed to yield during the working life. For these new products and their employing in different applications, and for the mentioned importance, this study has investigated the mechanical characteristics of these structures to avoid potential failure. An investigation of Arcan (shear V -notch test) procedure has been conducted for epoxy resin which is used for reimpregnations with Eglass and compared with lightweight metal of Aluminum as a benchmark to show the shear behavior for the composite one under shear load experimentally and numerically. The butterfly-shaped sample was modeled and tested accordingly with Arcan (shear V -notch test) numerically in order to produce pure shear force by tensile subjection condition using ANSYS software. The test verified that a state of pure shear was present during the testing on each ± 45∘ inclined from the axis of subjection although the changes recorded as G magnitude of shear modulus between Aluminum and the thermoplastic of Epoxy resin is nearby 94%, which may be because of the effect of material nature (i.e. mechanical properties) for the selected materials. The mentioned novel constituent shear behaviors have been investigated and compared expediently. These novel constituents can be adopted in different applications of shear loads. [ABSTRACT FROM AUTHOR]

Polysilazane (PSZ) is a class of novel materials with significant advantages; however, its practical applications are severely limited due to drawbacks such as the need for high-temperature curing and susceptibility to brittleness and cracking. Consequently, we have chosen PSZ and epoxy resin (EP) as the film-forming resins, with silica aerogel (SiO2gel) serving as the inorganic filler, to fabricate a SiO2gel–PSZ/EP composite coating capable of curing at room temperature. The incorporation of EP and SiO2gel has improved the toughness, mechanical stability, and thermal stability of PSZ. After 800 cycles of abrasion wear, the composite coating maintained its surface integrity. The scratch test rated its adhesion at level 1. Additionally, after 14 days of immersion in acidic and alkaline solutions, the coating demonstrated favorable chemical stability. The coating underwent 10 cycles of thermal shock testing, during which no significant cracking or peeling was observed on the surface. Finally, electrochemical impedance spectroscopy testing revealed that, after exposure to 300 °C, the composite coating exhibited a corrosion current density of 1.23 × 10−10 cm2, corresponding to a corrosion protection efficiency of up to 99.99%. In summary, the coating maintains excellent anticorrosion properties even after exposure to high temperatures and demonstrates outstanding stability, significantly enhancing its durability in harsh environments. This enhancement suggests a broad potential for applications in the field of subsea transportation. [ABSTRACT FROM AUTHOR]

The aim of the present study is to assess the shielding performance of a novel lead-free epoxide material against ionizing radiation. The effect of variation in particle size and concentration of tin oxide (SnO), which was added to epoxy resin polymer (ER), on its radiation shielding properties has been investigated in this research. Ten samples of ER samples incorporated with different concentrations (0%,20%,40%,60%) of SnO microparticles, nanoparticles, and both sizes combined were prepared and assessed. The linear attenuation coefficients (LAC) were measured experimentally through the collimated gamma-ray beam at 0.0595 MeV, 0.6617 MeV, 1.1730 MeV, and 1.330 MeV emitted from Am-241, Cs-137 and Co-60, respectively (to cover all energy range of gamma rays) for all samples with various concentrations and particle sizes of SnO. The other radiological shielding parameters such as half value layer (HVL), tenth value layer (TVL), and radiation protection efficiency (RPE) were estimated and compared for all different samples. The results prove that the increasing of the concentration and reducing the particle size of SnO leads to the enhancement of the radiation protection properties of the ER polymer. Moreover, it was observed that the incorporation of SnO micro- and nanoparticles together improves the radiation shielding properties of ER samples. Conclusively, the reinforcing of ER polymer material matrix by micro/nanoparticles of SnO as composite with enhanced radiation shielding specifications was highlighted. [ABSTRACT FROM AUTHOR]

The introduction of Diels–Alder (D-A) bonds into epoxy resins is a promising pathway to convert these unrecyclable materials into sustainable materials. However, D-A bonds make epoxy resins extremely brittle materials and hinder their practical usability. Nonetheless, the reversibility of D-A bonds allows the transition of the material to a de-crosslinked network formed by separated oligomers that can melt above 90–100 °C. This means that D-A epoxy resins can be reprocessed after being cured like thermoplastics. In the present work, a thermoset blend is made by adding spent epoxy particles to a D-A epoxy resin to increase its thermal and mechanical properties and to evaluate a possible reuse of conventional thermoset wastes. The application of hot-pressing to a mixture of epoxy particles and powder of cured D-A epoxy creates a material in which the interaction of the particles with the D-A resin increases the thermal resistance of the material and prevents the D-A epoxy from melting at high temperatures. In addition, the flexural strength is increased by 80% and the chemical resistance against organic solvents is also improved. [ABSTRACT FROM AUTHOR]

Epoxy adhesives possess excellent mechanical properties, durability, and stability in harsh environments, making them suitable for producing engineering materials. This study selects four commercially available epoxy adhesives in Saudi Arabia: Epotec YD 128; Sikadur®-52 LP; Sikadur®-31 CF; and Sikadur®-42 MP Slow. Firstly, a comparison of their storage, application, and service temperatures was made, detailing the hazard identification and prevention measures established in accordance with the Occupational Safety and Health Administration (OSHA) guidelines. Subsequently, test samples of the four adhesives were produced, and tensile, compressive, and shear tests were conducted to compare their fundamental mechanical properties. Finally, a gas analyzer assessed the major harmful gases emitted by these epoxy adhesives 120 min after mixing the epoxy resins and curing agents. The results show that Sika 42 exhibits the highest tensile and compressive strengths among other types of adhesives, reaching 75.7 MPa and 133.8 MPa, respectively. It also has the longest pot life of 48 min at elevated temperatures (40 °C), making it suitable for the climatic conditions in Saudi Arabia. However, as a three-component adhesive, its application is complex and associated with the most identified hazards. Sika 31 presents a tensile modulus of up to 10.4 GPa, at least 3.8 times higher than the other adhesives, making it practical for controlling tensile deformation. Additionally, its ultimate shear strain reaches 10.7%, at least 6.6 times higher than the other samples, highlighting its suitability for constructing ductile bonds. After mixing of epoxy resins with curing agents, the presence of NO2 and SO2 were detected. However, no harmful gases were detected after 120 min, possibly due to the complete curing of the adhesives. [ABSTRACT FROM AUTHOR]

Environmental awareness has led industries and consumers to replace products derived from oil resources with products derived from natural sources. In the case of the composite materials industry, the replacement of synthetic fibres with natural fibres has increased in recent years. To study the influence that different types of natural fibres and different textile manufacturing techniques have on the mechanical properties of composites, bio-based epoxy matrix composites reinforced with different natural animal fibres were produced, some reinforced with sheep's wool and others with dog wool, which were later subjected to bending and tensile tests. From the authors' knowledge, there are few studies of composites produced with animal fibres, and even fewer with dog hair. The textile structures used as reinforcement were created using crochet, knitting, and weaving techniques. Prior to the composites production, the fibres were characterized by X-ray Diffraction (X-RD), and the yarns produced from these fibres were subjected to tensile tests. The results obtained suggest that the number of yarns and the diameter of the needles used during the production of the reinforcement have a significant impact on the mechanical properties of the composites. The green epoxy resin composites reinforced with sheep's wool exhibit higher values of flexural strength, tensile strength, and Young's modulus than those reinforced with dog wool, with average increases of 36.97%, 45.16%, and 72.99%, respectively. It was also possible to verify that the composites reinforced with woven fabrics and crocheted fabrics exhibit the highest values of tensile strength, flexural strength, and Young's modulus. Additionally, the composites reinforced with woven fabrics exhibit the highest values of deformation at first failure/break and toughness. [ABSTRACT FROM AUTHOR]

Wrinkles are urgent problems to be solved in the process of hot diaphragm preforming. Inter-ply slipping resistance is one of the causes of wrinkles. In this paper, based on the vertical inter-ply slipping test system, the inter-ply slipping behaviors of carbon fiber-reinforced epoxy resin composite prepregs were characterized. The mechanism of wrinkles caused by inter-ply slipping resistance was analyzed. According to the different characteristics expressed by the fiber and resin during the slip process, the inter-ply slipping behaviors of the prepregs were divided into three stages. The effect of temperature on the inter-ply slipping stresses was shown. The temperature will affect the viscosity of the prepregs. When the viscosity of the prepregs is low, the inter-ply slipping resistance will decrease. Based on the Coulomb friction law and the hydrodynamic equation, the inter-ply slipping kinetic equation of the prepregs was established. The inter-ply slipping kinetic equation was introduced into the ABAQUS main program by the 'vfriction' subroutine. The introduction of inter-ply slipping dynamics improved the accuracy of predicting the shape and position of wrinkles. [ABSTRACT FROM AUTHOR]

It is widely known that glass–epoxy laminates are renowned for their high stiffness, good thermal properties, and economic qualities. For this reason, composite materials find successful applications in various industrial sectors such as aerospace, astronautics, the storage sector, and energy. The aim of this study was to investigate the mechanical and thermal properties of composite materials comprising two different types of epoxy resin and three different hardeners, both at room temperature and under cryogenic conditions. The samples were produced at IZOERG (Gliwice, Poland) using a laboratory hot-hydraulic-press technique. During cyclic loading–unloading tests, degradation up to a strain level of 0.6% was observed both at room temperature (RT) and at 77 K. For a glass-reinforced composite with YDPN resin (EP_1_1), the highest degradation was recorded at 18.84% at RT and 33.63% at 77 K. We have also investigated the temperature dependence of thermal conductivity for all samples in a wide temperature range down to 5 K. The thermal conductivity was found to be low and had a relative difference of up to 20% among the composites. The experimental results indicated that composites under cryogenic conditions exhibited less damage and were stiffer. It was confirmed that the choice of hardener significantly influenced both properties. [ABSTRACT FROM AUTHOR]

Among the many methods of joining different materials, gluing is characterized by its most specific nature. In comparison with, for example, welded, screwed, or overlapped connections, a glued connection depends on the largest number of factors. Many of them are related to the phenomenon of adhesion, which is complicated by definition. It has many shapes and forms, and its existence determines not only the durability of such a joint but also the possibility of its execution. Epoxy polymers are among the most commonly used adhesives. Their extremely good parameters can be easily modified by additives in the form of fillers. Compatibility between the filler and the adhesive allows for further improving the adhesive parameters in the glued joint. However, in order to effectively combine the adhesive and the filler, different, often specific mixing methods must be used. The following study presents the results obtained in an experimental research program, the aim of which was to increase the adhesion of epoxy resin to a properly prepared concrete substrate. As a method to increase the final adhesion, the addition of microsilica and carbon nanotubes in an experimentally determined amount was selected. The use of sonication as a mixing method together with cavitation allowed for improving the parameters which determine the final adhesion of the adhesive to concrete. The parameters which were selected to describe the course of changes in the adhesion of the adhesive to the concrete substrate were the viscosity, free surface energy, surface parameters, adhesion, and SEM images of the tested resin in various modification configurations. The obtained results make it possible to form stronger and more durable adhesive joints during the reinforcement of concrete structural elements using fiber-reinforced polymer (FRP) composites. [ABSTRACT FROM AUTHOR]

Epoxy resins exhibit outstanding curability, durability, and environmental compatibility, rendering them extensively utilized in the realm of engineering curing. Nevertheless, the current curing mechanism of epoxy-based resins in cohesion with sand remains inadequately elucidated, significantly impeding their applicability within the domain of soil curing. This study employed molecular dynamics simulations to investigate the adsorption behavior of three distinct types of epoxy resins on the sand surface: diglycidyl ether of bisphenol-A epoxy resin (DGEBA), diglycidyl ether 4,4′-dihydroxy diphenyl sulfone (DGEDDS), and aliphatic epoxidation of olefin resin (AEOR). The objective was to gain insights into the interactions between the sand surface and the epoxy resin polymers. The results demonstrated that DGEDDS formed a higher number of hydrogen bonds on the sand surface, leading to stronger intermolecular interactions compared to the other two resins. Furthermore, the mechanical properties of the adsorbed models of the three epoxy resins with sand were found to be relatively similar. This similarity can be attributed to their comparable chemical structures. Finally, analysis of the radius of gyration for the adsorbed epoxy resins revealed that AEOR exhibited a rigid structure due to strong molecular interactions, while DGEDDS displayed a flexible structure owing to weaker interactions. [ABSTRACT FROM AUTHOR]

Rare earth‐doped transparent glass, boasting high transmittance and excellent luminescent properties, holds great potential in the field of all‐inorganic solid‐state white illumination. Currently reported single‐structure solid‐state white lighting usually has the problems of low color rendering index (CRI) and high correlated color temperature (CCT) due to the lacking of red light emission. In this work, a novel single‐structure MgO–Al2O3–SiO2–Eu2O3 (MAS: Eu) glass with color tuning was prepared by the simple glass melting process. Interestingly, the prepared Eu3+‐doped aluminosilicate glass possessed a unique capability to achieve color emission under different excitation wavelengths. The reason for this was attributed to the good self‐reduction capability of the MAS glass, which effectively reduced Eu3+ to Eu2+ under an air atmosphere. Meanwhile, only by regulating the Eu3+ doping concentration, the MAS glass also achieved a tunable emission from blue to white to red light under 380 nm excitation. The acquisition of white light was realized through the multispectral emission of blue–green light emitted by Eu2+ and orange–red light emitted by Eu3+. Remarkably, the single‐structure MAS glass doped with 8 wt.% Eu3+ successfully achieved high‐quality white light and high thermal stability, exhibiting a high CRI of 86, a low CCT of 2761 K, good chromaticity parameters of (0.407 and 0.3192), and the emission intensity at 423 K remains above 86.35% that of room temperature. Meanwhile, the doped Eu3+ exceeded 12 wt.%, without any observable concentration quenching. Moreover, the MAS: Eu glass showed a high transmittance of 90 and a moderate thermal conductivity of 1.45 W/mK (epoxy resin ∼0.17 W/mK). These results would dramatically inspire the development of high‐quality solid‐state white lighting applications. [ABSTRACT FROM AUTHOR]

Water-based coating has gained much attention globally due to environmental issues. This work aims to develop a waterborne epoxy coating incorporated with modified natural rubber (NR) latex for improved performance. For this purpose, the NR latex was modified into three types of low molecular weight epoxidized natural rubber (LENR) latex. The waterborne epoxy resin was prepared by simply mixing the epoxy resin with an amine curing agent in water and various LENR latex contents (10 to 50 wt%). The waterborne epoxy/LENR blend was coated on a tin substrate and the cured coating demonstrated better adhesion and bending properties than the neat epoxy. Phase morphological properties displayed a rough surface with a heterogeneous surface structure of the dispersed rubber and epoxy matrix. Two glass transition temperatures were observed, corresponding to the rubber modifier and the epoxy matrix. The mechanical properties of the thermosetting epoxy/LENR blends were assessed, revealing a maximum increment in elongation ability by approximately 370% for adding 50 wt% LENR, compared to the neat epoxy. These results hold the potential avenue for utilizing NR-based material in the waterborne epoxy-based resin for coating applications. Furthermore, it contributes to the NR, a renewable and eco-friendly material, in the coating technology, embracing a sustainable future. [ABSTRACT FROM AUTHOR]

There is no doubt that when solid surfaces are modified, the functional groups and atoms directly bonded to solid atoms play a major role in adsorption interactions with molecules or resins. In this study, the adhesion and dissociation between epoxy resin and molecules containing Si atoms were analyzed. The analysis, conducted in contact with the solid surface of silicon, utilized quantum chemical calculations based on a molecular model. We compared some Si-containing molecular models to test quantum chemical calculations that contribute to the study of adhesion and dissociation between epoxy resins and solid surfaces somehow other than simple potential energy curve calculations. The AFIR (artificial force induced reaction) method, implemented in the GRRM (global reaction route mapping) program, was employed to separate an epoxy resin model molecule and three types of silicon compounds (Si(CH3)2(OH)2, Si(CH3)4, and (CH3)2SiF2) in three directions, determining their minimum dissociation energy when changing the applied energy by 2.5 kJ/mol. In systems with weak hydrogen bonds, such as Si(CH3)4 or (CH3)2SiF2, the energy required for dissociation was not large; however, in systems with strong hydrogen bonds, such as Si(CH3)2(OH)2, dissociation was more difficult in the vertical direction. Although anisotropy due to hydroxyl groups was calculated in the horizontal direction, dissociation remained relatively easy. [ABSTRACT FROM AUTHOR]

Preparation of high-performance thermosetting resins via bio-based resources is important for the development of a sustainable world. In this work, we proposed the introduction of cyanide structure groups into the molecular structure of epoxy resins to give them excellent heat resistance. A eugenol-based epoxy-phthalonitrile (EEPN) resin was synthesized by a two-step process using the bio-based renewable resource of eugenol, and a series of EEPN/Epoxide resin (E51) blend resins with different EEPN contents were prepared. The structure of the EEPN monomer was characterized and confirmed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and elemental analysis. The thermal stability and dynamic mechanical properties of the cured resins were investigated by thermogravimetric analysis and dynamic mechanical thermal analysis. The experimental results showed that EEPN had excellent heat resistance; the char yield at 800 °C was 67.9 wt%, which was much higher than that of E51 at 26.3 wt%; and the heat resistance of the blended resins was significantly improved with the increase in the EEPN content. [ABSTRACT FROM AUTHOR]

Epoxy resins (EPs) are highly flammable, and traditional flame retardant modifications often lead to a significant reduction in their mechanical performance, limiting their applications in aerospace and electrical and electronic fields. In this study, a novel flame retardant, bis(4-(((diphenylphosphoryl)oxy)methyl)phenyl)phenyl phosphate (DMP), was successfully prepared and introduced into the EP matrix. When the addition of DMP was 9 wt%, the EP/9 wt% DMP thermosets passed the UL-94 V-0 rating, and their LOI was increased from 24.5% of EP to 35.0%. With the introduction of DMP, the phosphoric acid compounds from the decomposition of DMP promoted the dehydration and charring of the EP matrix, and the compact, dense char layer effectively exerted the shielding effect in the condensed phase. Meanwhile, the produced phosphorus-containing radicals played a quenching effect in the gas phase. As a result, the peak heat release rate (PHRR) and total heat release (THR) of EP/9 wt% DMP were reduced by 68.9% and 18.1% compared to pure EP. In addition, the polyaromatic structure of DMP had good compatibility with the EP matrix, and the tensile strength, flexural strength and impact strength of EP/9 wt% DMP were enhanced by 116.38%, 17.84% and 59.11% in comparison with that of pure EP. This study is valuable for expanding the application of flame-retardant EP/DMP thermosets in emerging fields. [ABSTRACT FROM AUTHOR]

In this study, we address the challenge of hidden damages in FRP composites, such as delamination, matrix cracking, and fibre breakage resulting from transverse low-velocity impact (LVI)—damages often elusive on the surface. Our methodology operates at the meso-scale, depicting laminates as stacked homogenized plies incorporating interfaces. To capture the mechanical behaviour and damages, we extend an existing nonlinear mean-field debonding model (NMFDM), accommodating asymmetric matrix plasticity (AAMP), fibre–matrix interface debonding failure, and in-plane progressive failure. In a key enhancement, we introduce a strain rate term to the AAMP model, addressing strain rate effects associated with LVI loading. Additionally, we incorporate a novel strain-driven 3D failure criteria, offering a more precise assessment of progressive failure subjected to LVI loading. The interfaces between plies are modelled using surface-based cohesive behaviour to capture interaction phenomena. To validate the developed NMFDM, we conduct impact simulations at various energies on a UD composite laminate consisting of AS4/8552 carbon fibre and epoxy matrix. These simulations showcase the predictive capability and accuracy of the NMFDM in capturing the intricate behaviour and damage progression of UD composites subjected to LVI. [ABSTRACT FROM AUTHOR]

A three-dimensional viscoelastic-viscoplastic constitutive model is presented for predicting the dynamic mechanical behavior of an epoxy resin at low-to-medium strain rates. The model utilizes the generalized Maxwell model, incorporating two Maxwell elements in parallel with a nonlinear spring to represent the viscoelastic response at low and medium strain rates. By utilizing an empirical logarithmic relationship to predict the material properties at different strain rates, a nonlinear exponential relation based on overstress concepts is proposed for modeling the viscoplastic behavior. Comparing the tensile and shear stress–strain curves predicted by the proposed model with the experimentally measured curves, a good agreement is observed. Implementing the viscoelastic-viscoplastic model in commercial finite element software, a three-dimensional numerical discretization is performed. Through simulations of stress-relaxation and loading–unloading tests at various strain rates using the proposed material model, relaxation and hysteresis responses are analyzed. The model successfully predicts the experimentally measured hysteresis response of a specific epoxy resin during the loading cycle, consistent with other nonlinear viscoelastic models. This material model not only well replicates the nonlinear viscoelastic responses below the yield strain but also captures plastic nonlinearities at different strain rates. [ABSTRACT FROM AUTHOR]

Porous geopolymer composite (E51) reinforced by E51 epoxy resin was prepared by well‐distributed dual‐blending using red mud, metakaolin, and slag as raw materials. The effects of E51 content on microstructure, porosity, mechanical properties, and thermal insulation properties of the porous composites were investigated. The addition of E51 changed the setting time and viscosity of the slurry with high content of solid wastes (80%), which play an important role in the formation of pores during the direct foaming process. The addition of E51 had great influence on the porous properties of geopolymer composites, which in turn affected their compressive strength (0.19–1.44 MPa) and thermal conductivity (0.09–0.12 W/mK). The addition of E51 enabled the production of geopolymer composites in a rather large range of total porosity (67.3–81.1 vol%), with an optimal sample possessing a total porosity of up to 78.7 vol%, a thermal conductivity of 0.086 W/mK, and a compression strength of 0.47 MPa. [ABSTRACT FROM AUTHOR]

This paper presents the methodology developed in the repair of three oak beam ends in a protected heritage building: the Zabala Palace in Ordizia (Basque Country, Spain). It describes the structural assessment, design, calculation and execution process, as well as the experimental tests carried out in the laboratory to verify and validate the structural capacity of the repair method. The intervention consisted of cutting and removing the beam ends degraded by fungi and replacing them with wooden prostheses. These elements were connected to the beams by means of threaded steel rods and epoxy resin. Calculations based on standards and the literature were verified by laboratory tests where aspects such as the fluidity, filling and pull-out resistance of four commercial epoxy resins were tested. Once the epoxy resin was selected, three samples of the reinforcement design were also flexure tested. The results of the different tests show capacities much higher than those resulting from the application of the calculation procedures in the current bibliography and standards. The implemented solution allowed the conservation of most of the original patrimonial timber, following the criteria of minimum intervention. [ABSTRACT FROM AUTHOR]

Epoxy resin composite matrices reinforced with carbon fibers are highly demanded by certain industries such as the aeronautics industry because of their exceptional mechanical properties. Unfortunately, the use of reinforcing carbon fibers makes these composite materials hard to recycle by conventional methods. Therefore, in this study, specific hydrothermal treatments have been employed to recover carbon fibers from the offcuts of composite parts from the aeronautics industry. The resin decomposition rates (DRs) achieved by different settings of the operating parameters, such as the use of alkaline catalysts (KOH, NaOH, or K2CO3), the application of mechanical stirring, the use of different reaction times, the solvent volume/composite mass ratio, the specific surface area (surface area/mass) of the composite pieces, and the operating temperature and pressure (subcritical or supercritical conditions), have been examined and assessed. Under the conditions that have been evaluated, resin decomposition rates nearly as high as 98% have been achieved, while the recycled fibers retained over 95% of their original tensile strength (TS). [ABSTRACT FROM AUTHOR]

In this work, pretreatment with vacuum ultraviolet (VUV) light changed the adhesion strength between an epoxy resin and directly sputtered copper in a printed circuit board manufacturing process. The adhesion strength was 0.9 N/cm without irradiation but had a peak value of 2.1 N/cm at 540 mJ/cm2 of VUV irradiation; with increasing VUV irradiation, the adhesion strength decreased. Based on x-ray photoelectron spectroscopy (XPS) analysis of the copper interface of copper peeled from the resin, we evaluated the abundance ratio of metallic and organic oxygen at interfaces exposed to different VUV irradiation doses. We found that the change in the abundance ratio of metallic and organic oxygen was similar to the change in adhesion strength between copper and epoxy resin after exposure to different VUV irradiation doses. We observed the interface between copper and resin via scanning transmission electron microscopy (STEM) and found a distributed layer of oxygen. The functional group concentration in STEM images suggested the presence of a material with an intermediate density. We used chemically modified XPS to evaluate changes in the functional group concentration on epoxy resin surfaces irradiated with VUV light. We found that the hydroxyl group (OH) formed by VUV irradiation and the copper formed by direct sputtering improved adhesion strength in a synergistic manner. We observed a correlation between OH concentration on the resin surface and adhesion strength. These results will help to optimize the VUV irradiation process for adhesion between epoxy resin and sputtered copper. [ABSTRACT FROM AUTHOR]

This research addresses a gap in the literature by exploring the combined use of hemp and hemp hurds in composites, presenting a novel approach to bio-composite development. We report on the mechanical properties of epoxy resin composites reinforced with hemp fibers and hemp hurds, selected for their sustainability, biodegradability, and environmental benefits. These natural fibers offer a renewable alternative to synthetic fibers, aligning with the growing demand for eco-friendly materials in various industries. The primary objective was to evaluate how different filler contents and hemp hurd-to-hemp fiber ratios affect the composite's performance. Composites with 1:1 and 3:1 ratios were prepared at filler concentrations ranging from 1 wt.% to 10 wt.%. Tensile tests revealed that the 3:1 ratio composites exhibited better stiffness and tensile strength, with a notable UTS of 19.8 ± 0.4 MPa at 10 wt.%, which represents a 160% increase over neat epoxy. The 1:1 ratio composites showed significant reductions in mechanical properties at higher filler contents due to filler agglomeration. The study concludes that a 3:1 hemp hurd-to-hemp fiber ratio optimizes mechanical properties, offering a sustainable solution for enhancing composite materials' performance in industrial applications. [ABSTRACT FROM AUTHOR]

Carbon-reinforced polymer composites form an important category of advanced materials, and there is an increasing demand to enhance their performance using more convenient and scalable processes at low costs. In the present study, graphitic flakes were prepared by the mechanical exfoliation of synthetic graphite electrodes and utilized as an abundant and potentially low-cost filler to fabricate epoxy-based composites with different additive ratios of 1–10 wt.%. The morphological, structural, thermal, and mechanical properties of these composites were investigated. It was found that the thermal conductivity of the composites increases by adding graphite, and this increase mainly depends on the ratio of the graphite additive. The addition of graphite was found to have a diverse effect on the mechanical properties of the composites: the tensile strength of the composites decreases with the addition of graphite, whilst their compressive strength and elastic modulus are enhanced. The results demonstrate that incorporating 5 wt% of commercially available graphite into epoxy not only raises the thermal conductivity of the material from 0.223 to 0.485 W/m·K, but also enhances its compressive strength from 66 MPa to 72 MPa. The diverse influence of graphite provides opportunities to prepare epoxy composites with desirable properties for different applications. [ABSTRACT FROM AUTHOR]

The escalating impacts of climate change have led to significant challenges in maintaining road infrastructure, particularly in tropical climates. Abnormal weather patterns, including increased precipitation and temperature fluctuations, contribute to the accelerated deterioration of asphalt pavements, resulting in cracks, plastic deformation, and potholes. This study aims to evaluate the durability of a novel pellet-type stripping prevention material incorporating slaked lime and epoxy resin for pothole restoration in tropical climates. The modified asphalt mixtures were subjected to a series of laboratory tests, including the Tensile Strength Ratio (TSR) test, Indirect Tension Strength (ITS) test, Hamburg Wheel Tracking (HWT) test, Cantabro test, and Dynamic Modulus test, to assess their moisture resistance, rutting resistance, abrasion resistance, and viscoelastic properties. Quantitative results demonstrated significant improvements in the modified mixture's performance. The TSR test showed a 6.67% improvement in moisture resistance after 10 drying–wetting cycles compared to the control mixture. The HWT test indicated a 10.16% reduction in rut depth under standard conditions and a 27.27% improvement under double load conditions. The Cantabro test revealed a 44.29% reduction in mass loss, highlighting enhanced abrasion resistance. Additionally, the Dynamic Modulus test results showed better stress absorption and reduced likelihood of cracking, with the modified mixture demonstrating superior flexibility and stiffness under varying temperatures and loading frequencies. These findings suggest that the incorporation of slaked lime and epoxy resin significantly enhances the durability and performance of asphalt mixtures for pothole repair, making them a viable solution for sustainable road maintenance in tropical climates. [ABSTRACT FROM AUTHOR]

Epoxy resin, characterized by prominent mechanical and electric‐insulation properties, is the preferred material for packaging power electronic devices. Unfortunately, the efficient recycling and reuse of epoxy materials with thermally cross‐linked molecular structures has become a daunting challenge. Here, we propose an economical and operable recycling strategy to regenerate waste epoxy resin into a high‐performance material. Different particle size of waste epoxy micro‐spheres (100–600 μm) with core‐shell structure is obtained through simple mechanical crushing and boron nitride surface treatment. By using smattering epoxy monomer as an adhesive, an eco‐friendly composite material with a "brick‐wall structure" can be formed. The continuous boron nitride pathway with efficient thermal conductivity endows eco‐friendly composite materials with a preeminent thermal conductivity of 3.71 W m−1 K−1 at a low content of 8.5 vol% h‐BN, superior to pure epoxy resin (0.21 W m−1 K−1). The composite, after secondary recycling and reuse, still maintains a thermal conductivity of 2.12 W m−1 K−1 and has mechanical and insulation properties comparable to the new epoxy resin (energy storage modulus of 2326.3 MPa and breakdown strength of 40.18 kV mm−1). This strategy expands the sustainable application prospects of thermosetting polymers, offering extremely high economic and environmental value. [ABSTRACT FROM AUTHOR]

Based on the generalized results of experimental methods for studying the viscosity of oligomers—DSC, electron microscopy, NMR spin echo, x‐ray diffraction analysis, edge wetting angles, laser microinterference, atomic force microscopy, dynamic light scattering, plastic flow—an analysis of the features of the supramolecular organization of melts and solutions of epoxy oligomers was carried out. In terms of thermofluctuation approach, a qualitative assessment of the structural elements forming a macroscopic polymer body is given, and direct morphological evidence of their structure, thermodynamic stability, size evolution with temperature changes and elastic‐strain effects is presented. A mathematical apparatus has been developed to describe the destruction of domains in solutions and melts of oligomers. Analytical equations have been proposed for calculating the time of thermofluctuation relaxation of domains. Based on the analysis of the supramolecular structure of dian epoxy oligomers by transmission electron microscopy and translational mobility of oligomer macromolecules in the high temperature region (Tg + 150°C), it has been suggested that a structure such as "flickering clusters" of free volume elements is formed in the oligomer melts. Highlights: Phase diagrams of aromatic and aliphatic epoxy oligomers have been constructed.The influence of molecular weight on the activation energy of diffusion of viscous flow is estimated.It has been shown that the supramolecular structure of epoxy oligomers in the melt contains "flickering clusters."The lifetime of density fluctuations of epoxy oligomers domains in melts has been calculated. [ABSTRACT FROM AUTHOR]

The objective of this research is to develop a composite polymer coating with increased thermal conductivity and corrosion resistance for protecting structural materials in heat exchange apparatuses. Chemically pure compounds such as graphene, boron nitride, tyrosine, sodium hydroxide, zinc pyrophosphate, ethyl acetate, and epoxy resin with the addition of secondary polypropylene were utilized as raw materials. The obtained coatings were evaluated using an emission scanning microscope equipped with an energy‐dispersive spectroscopy (EDS) detector. Electrochemical activity was measured using standard equipment within a frequency range of 0.1–0.01 Hz. Thermal conductivity and corrosion resistance were measured at 0.24 W/m K and 9.70 Ω/cm2 when using only epoxy resin with the addition of secondary polypropylene. When employing a composite consisting of epoxy resin with the addition of secondary polypropylene, boron nitride, graphene, tyrosine, and zinc pyrophosphate, the thermal conductivity and corrosion resistance values were 1.65 W/m K and 11.10 Ω/cm2, respectively. Polymer coatings containing 30% composite demonstrated the highest thermal conductivity (1.65 W/m K) and corrosion resistance (11.20 Ω/cm2). The research findings can be utilized to create polymer coatings with enhanced thermal conductivity and corrosion resistance values. This polymer coatings could serve as structural materials for heat exchange devices. Highlights: Corrosion resistance increase with complexing of composite coating.Thermal conductivity increase with complexing of composite coating.Use of epoxy resin with secondary polypropylene make thermal conductivity value. [ABSTRACT FROM AUTHOR]

The waterborne epoxy resin (WER) colored antiskid thin layer has been widely used in asphalt pavement to improve driving safety. The tectonic depth determines the antiskid performance of aparticle antiskid type thin layer. The spalling of aggregate from a thin layer may reduce the tectonic depth, thus damaging antiskid performance. The spreading process of aggregate on the WER binder surface plays an important role in the spalling behavior of the thin layer. Herein, the influence of spreading processes on the ceramic aggregate spalling behavior on the WER thin layer was investigated based on laboratory experiments. The abrasion and British Pendulum Number (BPN) tests were employed to evaluate the antispalling and antiskid properties of the WER thin layers with different amounts of WER mortar, coverage rates of first-spread aggregate, and spreading orders of coarse/fine aggregates. Moreover, the tectonic depths of the layers before/after the spalling test were also investigated. The results indicated that the optimal dosage of WER mortar is 2.8 kg/m2. The WER thin layer exhibited better anti-striping property when coarse ceramic aggregate was spread first. The first-spread coverage rate of the aggregate on the WER surface is 70%. The thin layer exhibited a superior antispalling performance according to the resulting scheme, with a spalling rate of 3.77%. The tectonic depth only decreased from 1.87 to 1.80 mm after the spalling test. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of three toughening agents—core–shell rubber particles (CSR), nano-silica particles (NSPs), and epoxidized polybutadiene (EPB)—on the performance of UV-LED-cured epoxy electronic encapsulants. By systematically comparing the curing behavior, thermomechanical properties, and impact resistance of different toughening agents in alicyclic epoxy resins, their potential applications in more environmentally friendly UV-cured electronic encapsulation are evaluated. The results show that NSP and CSR toughened samples have fast cured speed under 365 nm UV-LED light, but it affects the depth of curing under low energy conditions. They maintain high Tg, high modulus, and low thermal expansion coefficient (CTE), especially in the NSP-toughened sample. The EPB-toughened sample has good transparency for LED, but it has negative effects on Tg and CTE. This research provides essential theoretical and experimental data to support the development of high-performance UV-LED-cured epoxy encapsulation materials. [ABSTRACT FROM AUTHOR]

As one of the most widely used thermosets due to its excellent performances, epoxy resin (EP) is widely used in various fields and often employed as a component of composite actuator devices, strengthening their mechanical properties. However, the expanding production of EP inevitably leads to the accumulation of waste end-of-life equipment and the corresponding increasingly serious environmental problems. This review summarizes the recycling strategies of EP, divided into two perspectives: recycling from wastes and sources. Chemical recycling is expected to be the future of waste EP treatment, and we discuss the chemical recycling methods of existing waste EP based on different mechanisms, including the selective cleavage of ester bonds, C–N bonds, and C–O bonds. On the other hand, epoxy vitrimer networks based on various dynamic covalent linkages are also outlined, which can respond to multiple external stimuli and provide materials with recyclability from the origin. Therefore, the use of epoxy vitrimer actuators can prevent waste generation throughout the whole lifecycle. We present some issues of concern in both waste-based and source-based recycling strategies and emphasize the significance of scaling-up. Finally, we summarized the current situation and present some future perspectives with the aim of making practical contributions to environmental issues. [ABSTRACT FROM AUTHOR]

Cementing, as an important part of the petroleum industry, plays a crucial role in ensuring the normal production and development of oil and gas resources. However, due to the brittle nature of Portland cement, it is prone to microcracks when subjected to downhole impact or vibration, which affects normal operations. Moreover, conventional elastic particles have a significant impact on the performance of cement paste, prompting people to continuously research new toughening admixtures. This article reviews the mechanism of toughening additives for oil well cement, the research status of physical toughening agents (fibers/whiskers, graphene) and polymer toughening agents (latex, epoxy resin, asphalt), aiming to provide reference and guidance for the development of new toughening additives. [ABSTRACT FROM AUTHOR]

Composite materials represent a cutting-edge formulation, combining two or more components to achieve multifunctional performance tailored for a range of multidisciplinary applications. In this study, it was focused on the fabrication of epoxy resin with glass fiber to produce a composite material. Furthermore, it explored the incorporation of carbon nanotubes (CNTs) into this formulation, paving the way for the development of self-healing composite sheets capable of withstanding bullet impacts. Characterization of the formulated composites involved a comprehensive comparative analysis utilizing attenuated total reflectance Fourier transform infrared spectroscopy (AT-FTIR) to assess chemical composition, alongside topographical studies employing scanning electron microscopy (SEM) and atomic force microscopy (AFM) to evaluate surface morphology as well as the thermal analysis study. Mechanical properties were rigorously analyzed using coherent gradient sensing (CGS) and mechanical testing methodologies. Our findings unveiled a remarkable compatibility between the epoxy resin and glass fibers in the presence of CNTs, indicating a synergistic enhancement in composite performance. Moreover, the remarkable self-healing capability post-bullet impact was substantiated through SEM imaging and advanced imaging techniques, affirming the efficacy of CNTs incorporation in bolstering composite resilience and durability. [ABSTRACT FROM AUTHOR]

Aim: To investigate the effects of Epigallocatechin gallate (EGCG) and curcumin, as a final irrigant on the fracture resistance of irradiated root that obturated with an epoxy resin sealer. Methodology: Eighty mandibular premolars were randomly divided into non-irradiated (NIR) and irradiated (IR) groups. The teeth were irradiated at 2 Gy per fraction, 5 times a week for a total dose of 60 Gy over 6 weeks. All specimens were decoronated, remaining 13±1 mm root length. Two groups were subdivided into four groups (n = 10): 1) non-instrumented; the intact root served as control. The other roots were instrumented with a pro-taper NiTi rotary system. The final irrigation used was 17% EDTA, followed by three irrigation solution groups; 2) 2.5% NaOCl, 3) 0.02% EGCG, and 4) 0.1% curcumin. Root canals were filled with gutta-percha and AH plus. All specimens were embedded in self-curing acrylic resin and loaded vertically at 1 mm/min until fracture occurred. Also, sealer penetration was assessed by confocal laser scanning microscopy (CLSM). The data were evaluated statistically using two-way ANOVA and Tukey test (α = 0.05). Results: In irradiated roots, fracture resistance of EGCG and curcumin groups did not differ from non-instrumented roots, but they were higher than the NaOCl group (P = 0.006). However, NaOCl, EGCG, and curcumin in irradiated roots had comparable strength that was higher than in the non-instrumented group (p<0.001). Difference between irradiated and non-irradiated roots was observed only for NaOCl and non-instrumented groups (P≤0.004). In irradiated roots, a higher sealer penetration was observed in EGCG and curcumin groups compared to NaOCl. Conclusion: EGCG and curcumin could be promising final irrigants to reverse the adverse effect of radiotherapy on the strength of irradiated roots obturated with AH Plus sealer. [ABSTRACT FROM AUTHOR]

Limestone calcined clay cement (LC3), enhanced through reactions with volcanic ash and the interaction between limestone and clay, significantly improves the performance of cementitious materials. It has the potential to cut CO2 emissions by up to 30% and energy consumption in cement manufacture by 15% to 20%, providing a promising prospect for the large-scale production of low-carbon cement with a lower environmental effect. To effectively manufacture LC3 concrete, this study utilized limestone (15%), calcined clay (30%), and gypsum (5%) as supplementary cementitious materials (SCMs), replacing 50% of ordinary Portland cement (OPC). However, in regions abundant in sulfate, sulfate attack can cause interior cracking of concrete, reducing the longevity of the building. To address this issue, microcapsules containing microcrystalline wax, ceresine wax, and nano-CaCO3 encapsulated in epoxy resin were prepared and successfully incorporated into LC3 concrete. Sulfate resistance tests were conducted through sulfate dry–wet cycles, comparing samples with and without microcapsules. The findings revealed that the initial mechanical and permeability properties of LC3 concrete did not significantly differ from OPC concrete. LC3 concrete with added microcapsules (SP4) exhibited enhanced resistance to sulfate attack, reducing mass loss and compressive strength degradation. SEM images displayed a mesh-like structure of repair products in SP4. After 14 days of self-repair, SP4 exhibited a 44.2% harmful pore ratio, 98.1% compressive strength retention, 88.7% chloride ion diffusion coefficient retention, 91.12 mV maximum amplitude, and 9.14 mV maximum frequency amplitude. The experimental results indicate that the presence of microcapsules enhances the sulfate attack self-healing performance of LC3 concrete. [ABSTRACT FROM AUTHOR]

This study is aimed at developing a fibre-reinforced polymer composite with a high bio-based content and to investigate its mechanical properties. A novel basalt fibre-reinforced polymer (BFRP) composite with bio-based matrix modified with different contents of star-like n-butyl methacrylate (n-BMA) block glycidyl methacrylate (GMA) copolymer has been developed. n-BMA blocks have flexible butyl units, while the epoxide group of GMA makes it miscible with the epoxy resin and is involved in the crosslinking network. The effect of the star-like polymer on the rheological behaviour of the epoxy was studied. The viscosity of the epoxy increased with increase in star-like polymer content. Tensile tests showed no noteworthy influence of star-like polymer on tensile properties. The addition of 0.5 wt.% star-like polymer increased the glass transition temperature by 8.2 °C. Mode-I interlaminar fracture toughness and low-velocity impact tests were performed on star-like polymer-modified BFRP laminates, where interfacial adhesion and impact energy capabilities were observed. Interlaminar fracture toughness improved by 45% and energy absorption capability increased threefold for BFRP laminates modified with 1 wt.% of star-like polymer when compared to unmodified BFRP laminates. This improvement could be attributed to the increase in ductility of the matrix on the addition of the star-like polymer, increasing resistance to impact and damage. Furthermore, scanning electron microscopy confirmed that with increase in star-like polymer content, the interfacial adhesion between the matrix and fibres improves. [ABSTRACT FROM AUTHOR]

[Display omitted] Enhancing the flame retardancy of epoxy (EP) resins typically entailed a trade-off with other physical properties. Herein, hyperbranched poly(amidoamine) (HPAA) and phytic acid (PA) were used to functionalize graphene oxide (GO) via electrostatic self-assembly in water to prepare a phosphorus-nitrogen functionalized graphene oxide nanosheet (PN-GOs), which could be utilized as high efficient flame-retardant additive of epoxy resin without sacrificing other properties. The PN-GOs demonstrated improved dispersion and compatibility within the EP matrix, which resulted in significant concurrent enhancements in both the mechanical performance and flame-retardant properties of the PN-GOs/EP nanocomposites over virgin EP. Notably, the incorporation of just 1.0 wt% PN-GOs yielded a 20.4, 6.4 and 42.7 % increases in flexural strength, flexural modulus and impact strength for the PN-GOs/EP nanocomposites, respectively. Furthermore, simultaneous reductions were achieved in the peak heat release rate (pHRR) by 60.0 %, total smoke production (TSP) by 43.0 %, peak CO production rate (pCOP) by 57.9 %, and peak CO 2 production rate (pCO 2 P) by 63.9 %. This study presented a facile method for the design of GO-based nano flame retardants, expanding their application potential in polymer-matrix composites. [ABSTRACT FROM AUTHOR]

The current study investigates the tensile behavior of SiC/SiC minicomposites, focusing on the efficacy of epoxy encapsulation in extracting the intrinsic fiber bundle response. Three minicomposite types were examined: two with Hi‐Nicalon Type‐S fibers and one with Tyranno ZMI fibers. Tensile tests were performed on minicomposites and fiber tows, both bare and epoxy‐encapsulated, whereas interface properties were measured via fiber push‐in tests. The results demonstrate that epoxy encapsulation partially mitigates non‐uniform loading in minicomposites with discontinuous matrices. Theoretical limits on fiber bundle strength, estimated using micromechanical models based on weakest‐link statistics and shear lag theory, are similar to measured encapsulated tow strengths when failure occurs within the elastic regime of the epoxy. In some cases, microstructural defects such as fiber–fiber contacts and debonded coatings play important roles in limiting composite strengths relative to theoretical values. Although encapsulation does not always directly improve properties, it provides useful context for evaluating composite performance and exposing microstructural limitations unaccounted for in idealized models. [ABSTRACT FROM AUTHOR]

To address the need for rapid in situ plugging and repair of hydraulic machinery and chemical pipelines and to resolve the issue that a single curing agent cannot simultaneously achieve rapid curing and excellent mechanical properties in epoxy resin systems, this study explores the use of composite curing agents. In particular, effective formulations are designed for mixing fast and slow curing agents, studying their effects on the curing behavior, curing quality, and mechanical properties of epoxy resins and elucidating their influence mechanisms. The results indicate that three resin systems meet the requirements for rapid curing (curing time within 30 min): 4A6B/EP, 2A8B/EP, and 0A10B/EP. Among them, 4A6B/EP exhibits the best curing quality and mechanical properties. In particular, 4A6B/EP demonstrates the lowest values of curing shrinkage rate, internal curing stress, average pore size, porosity, and cumulative pore volume. Its low internal stress and low defects reduce the stress concentration, while more efficient deflection and branching of internal cracks enhance its deformation resistance. Consequently, 4A6B/EP shows the highest microhardness, fracture toughness, tensile strength, Young's modulus, and elongation after fracture. Based on the comprehensive evaluation of rapid curing characteristics and mechanical properties, the 4A6B/EP system offers the best overall performance. Therefore, it is recommended as the preferred resin system for rapid plugging and repair of composite materials, providing a theoretical basis and technical support for boosting the application of epoxy resin composite materials in high-tech fields. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis, characterization, and application of four ionic liquids (ILs), three of which are being reported for the first time, with unique thermal properties and diverse anion-cation combinations, specifically in the context of epoxy resin polymerization. 1-3-Didodecylimidazolium dicyanamide (dDDIM DCA), 1-3-Didodecylimidazolium docusate (dDDIM DOSS), 1-ethyl-3-methylimidazolium dicyanamide (EMIM DCA), and 1-ethyl-3-methylimidazolium docusate (EMIM DOSS) were used to prepare six different mixtures with the same cation and with varying concentrations of DCA components, which is the main factor of an efficient polymerization, while the other component is intended to modify the properties of the cured resin. Mixtures based on EMIM cation demonstrated increased enthalpy and lower onset polymerization temperatures, indicating more efficient curing processes. The hardness of cured epoxy resins can be adjusted by altering the curing temperature and IL composition, with EMIM DCA and EMIM DOSS mixtures displaying high Shore A hardness, suitable for durable surface applications. In contrast, mixtures with higher dDDIM DCA proportions offered a balance between rigidity and flexibility, ideal for applications requiring both mechanical strength and elasticity. [ABSTRACT FROM AUTHOR]

This article explores the important, and yet often overlooked, solid-state structures of selected bioaromatic compounds commonly found in lignin hydrogenolysis oil, a renewable bio-oil that holds great promise to substitute fossil-based aromatic molecules in a wide range of chemical and material industrial applications. At first, single-crystal X-ray diffraction (SCXRD) was applied to the lignin model compounds, dihydroconiferyl alcohol, propyl guaiacol, and eugenol dimers, in order to elucidate the fundamental molecular interactions present in such small lignin-derived polyols. Then, considering the potential use of these lignin-derived molecules as building blocks for polymer applications, structural analysis was also performed for two chemically modified model compounds, i.e., the methylene-bridging propyl-guaiacol dimer and propyl guaiacol and eugenol glycidyl ethers, which can be used as precursors in phenolic and epoxy resins, respectively, thus providing additional information on how the molecular packing is altered following chemical modifications. In addition to the expected H-bonding interactions, other interactions such as π–π stacking and C–H∙∙∙π were observed. This resulted in unexpected trends in the tendencies towards the crystallization of lignin compounds. This was further explored with the aid of DSC analysis and CLP intermolecular energy calculations, where the relationship between the major interactions observed in all the SCXRD solid-state structures and their physico-chemical properties were evaluated alongside other non-crystallizable lignin model compounds. Beyond lignin model compounds, our findings could also provide important insights into the solid-state structure and the molecular organization of more complex lignin fragments, paving the way to the more efficient design of lignin-based materials with improved properties for industrial applications or improving downstream processing of lignin oils in biorefining processes, such as in enhancing the separation and isolation of specific bioaromatic compounds). [ABSTRACT FROM AUTHOR]