Base Epoxy Research Articles

Development of waterborne epoxy-based resin incorporated with modified natural rubber latex for coating application

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.

An experimental and analytical investigation to determine thermal conductivity of epoxy-filler composites for space applications

Thermal conductivity of epoxy-filler composite based Thermal Interface Materials (TIMs) is of utmost importance for thermal management systems used in space applications. Previous studies have shown that depending on the filler particle mixed into the epoxy, thermal conductivity of the composite can either be increased or decreased. Towards that, we have selected four different filler particles (micron sized) – aluminium, copper, zinc and silver to enhance the thermal conductivity of the base epoxy. Thermal conductivity of these 4 epoxy-filler composites has been determined experimentally using an indigenous developed setup at the temperatures ranging from 4.2 K to 323 K. The values have also been reported at various volume fractions (up to 15 %). In addition, after each preparation as the filler particles are mixed mechanically into the epoxy, they are randomly distributed, and this can affect the composite’s thermal conductivity (for the same volume fraction). The experimental determination of thermal conductivity for all the possible distributions is a time consuming, and cumbersome task. In the literature, thermal conductivity values are usually reported for few possible distributions. Therefore, we have developed a novel analytical model to predict all the possible values of thermal conductivity for a specific volume fraction. The predicted values compare well with our experimental data reported in this work at temperatures ranging between 338 K (above room temperature) to 4.2 K (liquid helium temperature). The predicted values are also in good agreement with the experimental values of different fillers such as red mud, pine wood dust and glass fiber etc. from the literature. Additionally, in comparison to other theoretical models like Lewis-Nielsen, Rule of mixture, and Poisson’s distribution, the present model predicts the thermal conductivity values more precisely. This work will be significant in the designing of components where heat transfer plays an important role towards the safety of the component.

Fabrication of kenaf fiber reinforced boron carbide fillers embedded epoxy matrix composite – An antimicrobial and structural analysis

This study investigates the incorporation of boron carbide (B4C) filler particulates into a kenaf fiber-reinforced epoxy matrix to explore its potential in lightweight applications, focusing on antimicrobial effectiveness, mechanical integrity, thermal properties, and microstructural characteristics. The composite material was formulated by blending varying seven different concentrations of boron carbide (0–50 g) and kenaf fibers (KFs) with an epoxy resin, aiming to achieve a balance between mechanical strength and minimal weight. Antimicrobial test revealed that the composite material, consisting of kenaf fiber reinforced with B4C particulates, exhibited significant antibacterial activity against common pathogens. Mechanical testing indicated that the addition of boron carbide and kenaf fibers significantly improved the tensile strength and flexural rigidity of the composites. Specifically, enhancements in tensile strength and flexural modulus were quantitatively analyzed, showing notable increases compared to the base epoxy resin. Scanning Electron Microscopy (SEM) was employed to examine the fracture surfaces following mechanical testing, revealing improved interfacial bonding between the kenaf fibers and the epoxy matrix due to the presence of boron carbide. This microscopic analysis also highlighted areas where stress distribution was optimized, contributing to the composite's enhanced mechanical properties.

Towards sustainable and recyclable plastic materials: Vanilin-based epoxy bio-composites with spruce bark powder and hydrochar, pioneering green chemistry solutions for shape memory applications

The negative impacts of fossil-based plastic production and its excessive usage are significant and multifaceted, affecting both the planet and humanity in various ways. In this study, a novel approach to developing sustainable and recyclable materials sourced from lignocellulosic biomass is introduced. This methodology involves formulating an epoxy-based resin using diglycidyl ether of vanillin (DGEVA) for curing with dodecenylsuccinic anhydride (DDSA), in presence of significant proportions (5–20 wt%) of either spruce bark (SB) powder or its hydrochar (HTC). Through thermomechanical analyses conducted via Dynamic Mechanical Analysis (DMA), it was ascertained that while the inclusion of SB has minimal impact on material performance, the incorporation of HTC leads to significant improvements. Specifically, a substantial enhancement in storage modulus is observed, increasing from 1.5 GPa to 3.1 GPa, and a rise in the damping factor from 56°C to 61°C. These findings are further corroborated by Scanning Electron Microscopy (SEM) analysis, which demonstrates excellent compatibility between the bioresin matrix and the biofillers. Moreover, this investigation underscores the remarkable mechanical and chemical recycling capabilities of the systems, which are notably improved by the presence of spruce bark or HTC particles, in addition to their inherent shape-memory properties. This approach not only showcases the feasibility of sustainable material development but also highlights the potential for an effective waste utilization in enhancing material properties and reducing the environmental impact.

Multifunctional epoxy coatings reinforced with LDHs-modified silica microspheres: Synergistic effects on corrosion resistance, thermal insulation, and flame retardancy

This research encapsulated hollow silica microspheres with Mg-Al layered double hydroxides (LDHs) via in-situ solution deposition, integrating them into an epoxy matrix to enhance its properties. Electrochemical impedance spectroscopy revealed that SiO2@Mg-Al-NO2-LDHs-EP maintained a high impedance of 1.42×109 Ω·cm2 after a 50-day immersion period, significantly outperforming the base epoxy. The impedance change in the scratch area in the local electrochemical impedance spectroscopy demonstrates the self-healing property of the coating. According to the thermal conductivity meter test results, adding SiO2-LDHs to the coating can reduce the thermal conductivity of the coating by about 20 %. Furthermore, microcalorimeter and cone calorimeter tests show that SiO2@Mg-Al-NO2-LDHs can significantly improve the flame retardancy properties of the coating. This study demonstrates the potential advantages of LDHs-coated silica microspheres in functional coatings.

The Formation of D-Allulose 3-Epimerase Hybrid Nanoflowers and Co-Immobilization on Resins for Improved Enzyme Activity, Stability, and Processability.

As a low-calorie sugar, D-allulose is produced from D-fructose catalyzed by D-allulose 3-epimerase (DAE). Here, to improve the catalytic activity, stability, and processability of DAE, we reported a novel method by forming organic-inorganic hybrid nanoflowers (NF-DAEs) and co-immobilizing them on resins to form composites (Re-NF-DAEs). NF-DAEs were prepared by combining DAE with metal ions (Co2+, Cu2+, Zn2+, Ca2+, Ni2+, Fe2+, and Fe3+) in PBS buffer, and were analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and X-ray diffraction. All of the NF-DAEs showed higher catalytic activities than free DAE, and the NF-DAE with Ni2+ (NF-DAE-Ni) reached the highest relative activity of 218%. The NF-DAEs improved the thermal stability of DAE, and the longest half-life reached 228 min for NF-DAE-Co compared with 105 min for the free DAE at 55 °C. To further improve the recycling performance of the NF-DAEs in practical applications, we combined resins and NF-DAEs to form Re-NF-DAEs. Resins and NF-DAEs co-effected the performance of the composites, and ReA (LXTE-606 neutral hydrophobic epoxy-based polypropylene macroreticular resins)-based composites (ReA-NF-DAEs) exhibited outstanding relative activities, thermal stabilities, storage stabilities, and processabilities. The ReA-NF-DAEs were able to be reused to catalyze the conversion from D-fructose to D-allulose, and kept more than 60% of their activities after eight cycles.

Strategies towards Fully Recyclable Commercial Epoxy Resins: Diels-Alder Structures in Sustainable Composites.

The Diels-Alder equilibrium is a widely known process in chemistry that can be used to provide a thermoset structure with recyclability and reprocessability mechanisms. In this study, a commercial epoxy resin is modified through the integration of functional groups into the network structure to provide superior performance. The present study has demonstrated that it is possible to adapt the curing process to efficiently incorporate these moieties in the final structure of commercial epoxy-based resins. It also evaluates the impact that they have on the final properties of the cured composites. In addition, different approaches have been studied for the incorporation of the functional group, adjusting and adapting the stoichiometry of the system components due to the differences in reactivity caused by the presence of the incorporated reactive groups, with the objective of maintaining comparable ratios of epoxy/amine groups in the formulation. Finally, it has been demonstrated that although the Diels-Alder equilibrium responds under external conditions, such as temperature, different sets of parameters and behaviors are to be expected as the structures are integrated into the thermoset, generating new equilibrium temperatures. In this way, the present research has explored sustainable strategies to enable the recyclability of commercial thermoset systems through crosslinking control and its modification.

The effects of temperature on mechanical properties of neat and montmorillonite reinforced epoxy compounds

ABSTRACT The aim of the article was to determine the effect of temperature on the tensile strength of two types of the epoxy compounds: the neat and the montmorillonite reinforced epoxy compounds. These epoxy compounds were made in four variants, which included two epoxy resins based on bisphenol A (unmodified base epoxy resin and modified with polyester resin epoxy resin) as well as two curing agents: triethylenetetramine and polyamide curing agent. The samples were exposed in two types of environment: (i) at 80°C for 1 and 2 months in a thermal chamber and also (ii) in the temperature range from −40°C to 80°C for 1 and 2 months in a thermal shock chamber. The reference samples of epoxy compounds were also compared. After the aging time, the dog-bone samples of epoxy compounds were subjected to the tensile strength tests in accordance with PN-EN ISO 527–2. The compressive strength of reference samples is higher for epoxy compounds containing the triethylenetetramine curing agent (both for epoxy compounds comprising Epidian 5 and Epidian 57 epoxy resin), The values of tensile strength, elongation at break are affected by the ambient and curing temperature, the curing period and the presence of a filler (montmorillonite). The tensile strength of the reference epoxy compounds containing Epidian 5 epoxy resin and the triethylenetetramine curing agent is lower than that of epoxy compounds containing unmodified epoxy resin (Epidian 5) and the polyaminoamide curing agent, while the tensile strength of the epoxy compounds containing modified epoxy resin (Epidian 57) and the triethylenetetramine curing agent is higher than that of the epoxy compounds containing Epidian 57 epoxy resin and the polyaminoamide curing agent. Aging of the epoxy compounds both in the climatic chamber and in the thermal shock chamber in most cases it contributed to an increase in the tensile strength.

Evaluation of disposable protective garments against epoxy resin permeation and penetration from anti-corrosion coatings.

Epoxy-based resin formulations are a frequent cause of allergic and irritant contact dermatitis in the construction and painting industries. Cases of epoxy resin contact dermatitis continue to persist across many sectors and are likely attributable to the growing use of epoxy products, including epoxy-based anti-corrosion coatings and inadequate skin protection. There are no published performance data against epoxy resins for garment materials and gloves to guide proper material selection in the workplace. The objective of this study was to evaluate the resistance of 5 protective garment materials against permeation and penetration by bisphenol A diglycidyl ether and its higher oligomers found commonly in epoxy-based anti-corrosion coatings. Five disposable garment materials were evaluated for resistance to bisphenol A diglycidyl ether monomers and oligomers during contact with epoxy-based anti-corrosion coatings, including latex gloves, nitrile gloves, Tyvek coveralls, polypropylene/polyethylene (PP/PE) coveralls, and a cotton T-shirt. A permeation test cell system was used to evaluate each garment material against an epoxy-based zinc-rich primer and an epoxy-based intermediate coating using a realistic application method. Glass fiber filters were used to collect permeating and penetrating epoxy resin during a 120-min test period. Bisphenol A diglycidyl ether quantification was performed with high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Paint loading, coating thickness, and homogeneity were assessed on polytetrafluoroethylene filters sprayed in series in permeation test cells. Latex gloves provided the least resistance to permeation by BADGE in coating formulations, with a maximum cumulative permeation over the 2-h test interval of 21.7 ng cm-2 with the primer and 513.8 ng cm-2 with the intermediate coating product. Nitrile gloves were not permeated by either coating formulation. The Tyvek coveralls provided greater protection as compared to the PP/PE coveralls. The cotton T-shirt was penetrated by bisphenol A diglycidyl ether more frequently than any of the tested garment materials and resulted in a maximum cumulative penetration of 128 ng cm-2 with the primer and 28.0 ng cm-2 with the intermediate coating. Although all the garment materials evaluated during this study provided sufficient protection to prevent cumulative permeation in excess of the established acceptable permeation thresholds, the use of nitrile gloves and Tyvek coverall is highly recommended to minimize skin exposure to bisphenol A diglycidyl ether. We recommend cotton T-shirts to be used under Tyvek coveralls as a secondary layer of skin protection and for added comfort, but not as a primary protection layer.

Functionalized borosilicate-silica-epoxy nanocomposite superhydrophobic coating for corrosion inhibition under harsh environment

Current work proposes a facile scheme for fabrication of robust superhydrophobic borosilicate-silica-epoxy nanocomposite coatings on steel substrate with hierarchical structures, capable of inhibiting corrosion under harsh environment. The scheme amalgamates the advantageous properties of three ingredients: acid resistant property of borosilicate glass, superhydrophobic features of functionalized silica nanoparticles and durability of epoxy resin. The various steps of synthesis include 1. ball milling of borosilicate glass to micron and submicron size (~500 nm to 1.5 μm) 2. grafting of silica nanoparticles (~20 nm, through stober method) on the borosilicate particles to form rough hierarchical structure and 3. preparation of stable dispersion of the nanoparticles in epoxy-based resin followed by coating through immersion technique. Efficacy of the scheme was established through morphological, durability and electrochemical impedance studies. The surface morphology revealed hierarchical structures of functionalized silica nanoparticles (size range 20–100 nm) grafted on micro-sized borosilicate particles, which sustained water droplets with contact angle as high as 164.5° ± 2°. Sandpaper abrasion test proved excellent durability retaining hydrophobicity up to 250 abrasion cycles. The prepared surface maintained notable interface stability under aggressive environment: 3 and 10 days under pH 1 and 13 respectively. The electrochemical study in 3.5 wt% NaCl aqueous solution showed significant decrease in corrosion current density of coated surface (0.3585 μA/cm2) compared to uncoated surface (43.918 μA/cm2) suggesting excellent corrosion resistance. The results highlight scope of using this robust coating for abrasive and harsh environment.

Electrochemical Evaluation of Al-5 wt% Zn Metal-Rich Primer for Protection of Al-Zn-Mg-Cu Alloy in NaCl

An intact and X-scribed Al-5wt%Zn-rich primer (AlRP) without pretreatment or topcoat was evaluated for its ability to suppress potential-dependent intergranular corrosion and intergranular stress corrosion cracking of peak-aged AA7075A-T651 in NaCl salt fog and full immersion. The ability of the primer to provide sacrificial anode-based cathodic prevention of peak-aged AA7075-T651 substrate was evaluated both under the primer coating and at scratches. The AlRP evaluated consisted an epoxy-based resin embedded with spherical Al-5wt%Zn pigment particles. Performance was evaluated under full immersion in 0.6 M NaCl solution and compared to ASTM B117 salt spray exposure using two approaches. These consisted of the University of Virginia (UVA) cycle test on intact coatings and the full immersion galvanic couple testing on simulated scratched panels created when intact coatings form bimetal couples with bare AA7075-T651. Focus was placed on the ability of the AlRP to achieve a targeted intermediate galvanic couple potential near a “prevention” potential which suppresses stress corrosion crack growth, intermetallic particle corrosion as well as intergranular corrosion. The long-term (24-h) open-circuit potential (OCP) of AlRP-coated AA7075-T651 in 0.6 M NaCl indicated that the AlRP provided less than 100 mV of cathodic potential shift of the intact coating from its OCP in 0.6 M NaCl. Electrochemical cycle testing conducted at a potentiostatic hold of –0.95 VSCE demonstrates that the AlRP did not enable sacrificial anode-based cathodic protection as the coupled potential remained at the corrosion potential of bare AA7075-T651. Furthermore, the current observed throughout galvanic corrosion experiments coupling of AlRP to AA7075-T651 indicated the AlRP coating was a cathode in the bimetal galvanic couple. ASTM B117 salt spray exposure of the AlRP revealed oxidation of the AA7075-T651 substrate below the primer detected as a continually growing oxygen signal at the primer-substrate interface that did not arrest corrosion over the exposure period.

Degradable, intrinsically flame-retardant, low-water-absorbing vanillin-derived epoxy thermoset with a Schiff base structure

Given the issues of non-renewability, poor degradability, and high flammability associated with petroleum-derived bisphenol A-type epoxy (DGEBA) resins, developing degradable and flame-retardant epoxy resins from renewable biomass is of great importance. However, it is still a challenge at present. Herein, a novel Schiff base diepoxy compound (BV-EP) was successfully synthesized from lignin-derived vanillin and commercial amine 9,9-Bis(4-aminophenyl)fluorene (BAPF) through a simple, two-step procedure. After cross-linking with 4,4ʹ-diaminodiphenylmethane (DDM), the vanillin-derived Schiff base epoxy thermoset (BV-EP/DDM) displayed better thermal properties (glass transition temperature Tg: 197 °C) and flame retardancy than the control sample (DGEBA/DDM). The peak heat release rate (PHRR) and the total heat release (THR) of BV-EP/DDM were reduced by 60.1 % and 19.8 %, respectively, compared with those of DGEBA/DDM. Furthermore, the degradable Schiff base and the hydrophobic fluorenyl Cardo structure provide the BV-EP/DDM with good acid-catalytic degradation and low water absorption properties. In this work, the fluorenyl Cardo structure plays the role of “killing three birds with one stone” in enhancing the performance of BV-EP/DDM. This synergistic strategy paves the way for fabricating more practical degradable and intrinsically flame-retardant epoxy resins from renewable biomass resources.

From stress to charge: investigating the piezoelectric response of solvate ionic liquid in structural energy storage composites.

Solvate ionic liquids (SILs) are a class of ionic liquids where the liquid-state salt is chelated by a coordinating solvent, and of interest due to their advantageous properties such as low vapour pressure and superb thermal and chemical stability for energy storage applications. The electromechanical and piezoelectric effect were studied in lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solvated by triethylene glycol dimethyl ether (triglyme, G3), forming [Li-G3]TFSI. These effects were also investigated in full solid polymer electrolyte (SPE) used in energy storage devices, consisting of [Li-G3]TFSI paired with an epoxy-based resin system. The SIL's electromechanical response was first established in isolation, as well as within the SPE. Experimental data demonstrates the effect of a major part of the SPE contributing to the electrical potential generation during application of force and subsequent pressurisation as well as depressurisation, underlined by a direct piezoelectric effect. SPE response to applied load is explored after the recent discovery of liquid-to-crystalline phase transition following pressurisation in pure ionic liquids. This finding has the potential to ameliorate the performance of energy storage composites via additional effects of charging such a device by subjecting it to stress, leading to increased efficiency. Results to date show a bulk potential difference across the SIL of up to 150 mV, while the SPE potential response is scaled down due to a significantly lower volume of SIL at the interface (∼30 mV). Nevertheless, such findings can still significantly affect the performance of carbon fibre (CF)-based structural supercapacitors and batteries that are able to store and release electrical energy whilst simultaneously contributing to load-bearing performance.

Scientific Analysis and Conservation Treatment of the Ancestral Tablet Excavated from the Site of Gongpyeong, Seoul

Scientific analysis and conservation treatment were conducted on two ancestral tablets excavated in whole form the site of the 15th and 16th districts (B area) in Gongpyeong, Seoul. As a result of scientific analysis, a rectangular empty space was confirmed inside the ancestral tablet that could not be seen with the naked eye. It was a form of manufacturing and combining a main body and a prop composed of the front side and the back side, and the tree species of all the members of the two ancestral tablets were identified as Castanea spp.. It is supposed that the two ancestral tablets excavated from the Gongpyeong site were manufactured in accordance with the standard and shape similar to the contents of “Garye”, which has records on the production of ancestral tablets. The excavated ancestral tablets were immersed to the final 40% using PEG#2000 by applying the PEG immersion method, and dried using a vacuum freeze dryer. After drying, disparate things such as PEG and soil remaining on the surface were removed, and PEG#4000 15% (in ethyl alcohol) was applied to the surface once to the surface to strengthen the surface. A slight crack was observed in a part of a prop of one of the two ancestral tablets, and it was restored using epoxy-based resin, color-matched, and conservation treatment was completed.

Digital light 3D printed fast- and controlled degradation of covalent hydrogel networks

Digital light processing (DLP)-based 3D printing of hydrogels with sophisticated structures has been widely used in myriads of fields. However, the inherent covalently crosslinked network of hydrogels limits their further applications, such as working as sacrificial molds. In this work, a photocurable hydrogel system with labile covalent bonds suitable for DLP based printing to fabricate 3D complex hydrogel structures with fast- and controlled degradation ability is reported. The hydrogel precursor is composed of polyethylene glycol 400 (PEG400), a water soluble photoinitiator, and PEGDA575-Do, a degradable photocurable diacrylate monomer that can be degraded in aqueous condition via reversable aza-Michael addition reaction. The mechanical properties of formed hydrogels can be regulated by changing the PEG content and water content, and the degradation rate can be regulated by changing parameters such as PEG400 content, water content and the treating temperature. Moreover, the DLP printed degradable hydrogels networks can be used as sacrificial molds to fabricate structures from materials that cannot be directly used for DLP 3D printing (e.g. thermoplastic polycaprolactone (PCL), epoxy-based resin, and chocolate). As proofs-of-concept, a microfluidic chip is fabricated by using the biocompatible 3D printed hydrogel as a sacrificial template. Similarly, a flexible RFID tag and a flexible self-powered device are also prepared, demonstrating the potential applications in the field of flexible electronics.

Impact of water diffusion on electrical properties of epoxy nanocomposites

This study investigates the effects of water ageing at 80 °C on glass fibre hybrid epoxy nanocomposites with multi-walled carbon nanotubes and graphene nanoplatelets. Effect of water uptake in the epoxy matrix is mitigated by the inclusion of carbon nanofillers, leading to improved hydrophobic nature. A comparative study is performed on the water uptake of the epoxy-amine matrix cured with aliphatic amine, with 0.4 weight percent of MWCNT and 0.6 weight percent of graphene nanoplatelets (GNPs). Gravimetric assessment and electrical impedance measurements are carried out over a period of 3000 h to assess water diffusion coefficients and water saturation. Water absorption is measured until saturation, and results show that the water diffusion coefficient of the hybrid nanocomposites is increased from 2.51 × 10−8 (m2 s−1) at 27 °C to 3.32 × 10−8 (m2 s−1) at 80 °C and it is higher than that of the base epoxy composites. Cole–Cole diagrams have revealed heterogeneity of the composites studied. Water diffusion results in the plasticization of the matrix, and it manifests in the broadening of the tanδ peak observed in water-aged epoxy composites. With the inclusion of hybrid MWCNT and GNP nanofillers.,the water diffusion coefficient is reduced to half, and saturation is increased by four times.

Block copolymer additives for toughening 3D printable epoxy resin

We explore the potential for using a brush-coil triblock copolymer to enhance the mechanical properties of epoxy resin for 3D printing applications. Epoxy resins are widely used in structural material and adhesive and have great potential for 3D printing. However, the highly brittle nature of epoxy resins requires the use of large concentrations of toughening agents that pose significant challenges in meeting rheological requirements of 3D printing. We report a reactive brush-coil block copolymer with three distinct blocks that can phase separate and chemically crosslink with the base epoxy resin to form spherical aggregates. Detailed scanning electron microscopy imaging shows that these aggregates can arrest and deflect cracks during propagation and can synergistically strengthen (∼ 1.5×) and toughen (∼ 2×) the epoxy resin with even 1 wt% of the BCP additive to the base resin. Importantly, both the modulus and the glass transition temperatures are preserved. Direct ink writing (DIW) and digital light processing (DLP) 3D printing of the modified resins also shows the same strengthening and toughening effects seen in mold-cast samples, demonstrating its compatibility with 3D printing processes. These findings suggest that brush-coil triblock copolymers additives at very low concentrations can synergistically improve the mechanical properties of epoxy resin for 3D printed parts.

Optically transparent and high-strength glass-fabric reinforced composite

Fiber reinforced polymer composites (FRPs) are widely utilized in various industrial applications due to their significant advantages such as low cost and superior mechanical properties. However, owing to the trade-off between high mechanical strength and high optical transparency with typical FRPs, it is technically challenging to achieve high mechanical performance while meeting the optical requirements for transparent electronics and automotive applications. We herein report the synthesis of a transparent fiber reinforced polymer (tGFRP) by incorporating reinforced E-glass fiber into refractive-index-tunable thermosetting epoxy resin and the consequential advantageous opto-mechanical properties. By doping organic molecules, the optical property of the epoxy-based resin system has been efficiently engineered, achieving the match of the chromatic dispersions of the E-glass fiber and the epoxy resin. By the means of a novel technique derived from infusion treatment and in-situ polymerization combined with a liquid composite molding (LCM) method, both surface and bulk defects have been efficiently mitigated. With the refractive-index of the epoxy matrix matched with that of the embedded fiber fabrics, high transparency up to 88% has been realized with 10v.% fiber loading (500 μm thick tGFRP). An outstanding transparency and superior mechanical properties were achieved on 2 mm thick samples, maintaining up to 85% transmittance even when using 25 layers of E-glass fabric, corresponding to 50 v.% fiber. This work has shed light on the development of transparent composite materials for applications such as in construction, transportation, and protective equipment.

Ti3C2Tx MXene coated carbon fibre electrodes for high performance structural supercapacitors

MXenes, while excellent for electrical energy storage, face challenges in translating their nanoscale properties to macroscale structures. To address this, MXene-coated carbon fibers (CF) were developed as electrode materials for structural supercapacitor composites. CF surface chemistry was tailored using aryl diazonium salts (–NO2, –NH2, -SH, –COOH) to optimize MXene adhesion. Electrodes were characterized for surface chemistry, morphology, and properties including electrochemical, mechanical, and interfacial aspects. Electrodes developed from MXene coated on CF functionalized with a poly(o-phenyelenediamine) coating exhibited a specific capacitance of 157 F/g−1 at 5 mV s−1, a ∼725-fold improvement in capacitance compared to pristine unfunctionalized CF, with minimal to no compromise in the underlying strength and stiffness of the CF. The MXene coating also improved the interfacial adhesion of the electrode to an epoxy-based resin by 54 %. The process was scaled up to functionalize and coat woven CF mats and were used to fabricate a structural supercapacitor device. The device exhibited a specific capacitance of 908 mF/g−1 at 0.5 mA g−1, representing a remarkable ∼42-fold improvement compared to the control. This lightweight multifunctional supercapacitor composite holds great potential in aerospace, automotive, and renewable energy storage sectors, addressing global challenges tied to fossil fuel combustion and associated environmental and socio-economic issues.

Effect of Different Silane Coupling Agents on the Bond Strength between Hydrogen Peroxide-Etched Epoxy-Based- Fiber-Reinforced Post and Composite Resin Core.

The aim of the study was to evaluate the effect of various silane coupling agents on the micro-push-out bond strength between a hydrogen peroxide-etched epoxy-based fiber-reinforced post and composite resin core. Seventy-five cross-linked epoxy-based fiber-reinforced posts were etched with 24% hydrogen peroxide for 10 min. Then they were divided into five groups according to various silane coupling agents and bonded to a composite core. A Universal Testing Machine was utilized to evaluate the push-out bond strength. In addition, all groups' modes of failure were assessed. The push-out bond strength data in MPa were analyzed using ANOVA and a Tukey HSD post hoc test to reveal any difference between the groups. Results revealed that the application of a two-bottle silane coupling agent exhibited the highest bond strength, while the application of a one-bottle silane coupling agent demonstrated the lowest bond strength for a hydrogen peroxide-etched fiber post bonded to a composite core material, which was statistically significant (p < 0.05). The strongest association with the highest bond strength was found with the two-bottle silane coupling agent when compared to the one-bottle. The study highlighted that the application of a silane-coupling agent may affect the bond strength between composite and epoxy-based fiber-reinforced posts.