Diglycidyl Ether Of Bisphenol A Research Articles

UV-assisted direct ink writing 4D printing of benzoxazine/epoxy thermosets

Benzoxazine is employed in an increasing number of domains due to its exceptional thermal stability, but it is difficult to apply for 4D printing due to its high brittleness and lack of photo-curable groups. Herein, dual-cure DIW 4D printing inks (BZs) consisting mainly of a commercial benzoxazine and a synthesized diglycidyl ether bisphenol A monoacrylate (DGEBAMA) were formed. In the dual-cure ink, photo-curable groups were cross-linked to rapidly prototype complex structures. After thermal curing, 4D-printing structures with isotropic properties were obtained. The ether bonds provided by the copolymerization of epoxy groups and oxazine rings and the soft segment of DGEBAMA increased the material's toughness. The highest overall performance was obtained by BZ50, which displayed higher glass transition temperature (188 °C), tensile strength (92.13 MPa), elongation at break (9.34 %), and good shape-memory ability. This work provides a straightforward method for enabling the 4D printing of benzoxazine/epoxy-based materials with good toughness, excellent thermal properties, and shape-memory abilities, expanding the potential application of benzoxazine/epoxy-based materials in advanced fields.

Pyrolytic performance and kinetics study of epoxy resin in carbon fiber reinforced composites: Synergistic effects of epoxy resin and carbon fiber

Pyrolysis is recognized as a sustainable approach for recycling carbon fiber reinforced polymers (CFRP), ensuring enhanced process efficiency and resource utilization. To unveil the pyrolysis mechanism of epoxy resin and its synergistic interaction with carbon fiber in different scenarios, we conducted pyrolysis experiments on pure epoxy resin diglycidyl ether of bisphenol A cured with 4,4'-Diaminodiphenylmethane (C-epoxy), as well as three kinds of carbon fiber-resin mixtures, using TG and Py-GC/MS techniques. Isoconversional analysis (Friedman method) of C-epoxy degradation revealed three reaction stages within the temperature range of 280–540 °C, each corresponding to activation energies of 158 kJ/mol at α = 5%, 179–190 kJ/mol at the plateau of α = 10–60%, and 190–236 kJ/mol for α values surpassing 60%. The multi-Gaussian distributed activation energy model (DAEM) aptly characterized C-epoxy’s thermal decomposition, featuring two Gaussian peaks with similar contributions of 0.58 and 0.42, and activation energy distributions of 217.76 ± 3.92 kJ/mol and 233.36 ± 21.42 kJ/mol, respectively, which are close to the activation energies from isoconversional analysis at α = 10–60% and α > 60%, respectively. The presence of carbon fiber significantly influenced the kinetic parameters of epoxy resin pyrolysis, with the extent of change linked to the mixing methodology applied. Notably, carbon fiber decreased the activation energy of the reaction while accelerating the rate of weight loss. However, the synergistic effects vary depending on different synergistic scenarios. By analyzing the product distribution obtained through an analytical pyrolyzer coupled with a gas chromatography–mass spectrometry set-up (Py-GC/MS), we proposed a pyrolysis mechanism for epoxy resin, encompassing three key stages: cleavage of N–C and NC–COH bonds, phenolic O–C and vicinal C–C bonds, and disruption of the isopropylidene bridge on bisphenol A. The influence of carbon fiber on epoxy resin pyrolysis product distribution was relatively modest, manifesting predominantly within the mixture obtained by premixing before curing. Here, carbon fiber exhibited a dual effect, inhibiting oxygen-containing diphenyl products while promoting oxygen-containing monophenyl products. Ultimately, our study provides essential kinetic data for multidimensional simulation and theoretical guidance pertaining to the pyrolysis recycling of widely used carbon fiber-reinforced epoxy resin composites.

Rheology, curing and time‐dependent behavior of epoxy/carbon nanoparticles systems

AbstractThis study delved into the characterization of epoxy nanocomposites containing diglycidyl ether of bisphenol‐A (DGBEA), graphene nanoplates (GN), and carbon nanotubes (CNT) across a range of weight percentages (0.05% to 2%). The nanocomposites were produced through a process involving mechanical stirring and ultrasonication. To assess compatibility, three‐dimensional solubility parameters (3DSP) were employed. CNT demonstrated superior compatibility with epoxy and triethylenetetramine (TETA), due to its higher amount of oxygenated species in nanoparticle surface compared to GN. A rheological percolation phenomenon occurred in CNT systems at concentrations above 0.2%, while GN did not display percolation even at 2% concentration. Incorporating nanoparticles led to increased curing enthalpy due to surface functional groups. As the percolation network formed, viscosity rose, and a reduced glass transition temperature (Tg) indicated restricted molecular mobility. Surprisingly, Tg consistently increased by approximately 27°C during composite annealing, regardless of nanoparticle type or concentration. This was attributed to forming a three‐dimensional network structure potentially originating from reactions between nanoparticle‐oxygenated groups and the epoxy matrix. This phenomenon was crucial in heightened creep and irreversible deformations, setting these nanocomposites apart from pure resin behavior.

Activation of inert triethylene tetramine-cured epoxy by sub-critical water decomposition

Cured epoxy is stable and difficult to be recycled. To make the inert cured epoxy and its derivatives or composites reactive is still a challenge. In this study, sub-critical water was used to decompose the solid diglycidyl ether-based epoxy resin (bisphenol A and bisphenol F) cured with triethylene tetramine (TETA) to reactive species. First of all, the thermally most unstable bonds in the epoxy resin underwent homogeneous cleavage reaction. Next, the generated free radicals were saturated by extracting hydrogen from the sub-critical water. The decomposition rate was improved with increasing the temperature and reaction time. During the reaction, breakage occurs preferentially in the epoxy resin main chain because of the existence of ether groups. The compounds evolved and the decomposition was analyzed. The experimental outcomes revealed that the decomposition mechanism of diglycidylether of bisphenol A (DGEBA)/TETA and diglycidylether of bisphenol F (DGEBF)/TETA resin regimes in sub-critical water may include side group elimination, random fracture and unzipping. Moreover, a segmented second-order kinetic analysis of the decomposition process was performed. The decomposition processes of two resins in sub-critical water were divided into two stages. Both stages were second-order reaction, the activation energy of DGEBA/TETA was 175 kJ/mol (Ea1(15-45min)), and 612 kJ/mol (Ea2(52.5-75min)). The activation energy of DGEBF/TETA was 258 kJ/mol (Ea1(15-45min)), and 686 kJ/mol (Ea2(52.5-75min)), respectively. This study provides a way for recycling inert epoxy wastes from different industrial fields and generating reactive and functional polymers.

Synergistic effects in the co-pyrolysis of thermoset epoxy resin and biomass on kinetics and product distribution

With the rapid growth of wind power, batteries, and aerospace industries, sustainable disposal of thermoset plastics has become a long-term concern. However, pyrolysis, a highly promising solution for this issue, has seen limited studied on thermoset plastics. Drawing inspiration from the synergistic interactions observed between thermoplastics and biomass, this study explored the co-pyrolysis of a thermoset epoxy resin, diglycidyl ether of bisphenol A, cured with 4,4′-Diaminodiphenylmethane, with ash-free biomass pseudo-components (cellulose, lignin, and xylan) using thermogravimetry and Py-GC/MS. The results revealed distinctive synergistic effects in Epoxy-Cellulose and Epoxy-Lignin mixtures, delaying the onset and hastening the conclusion of weight loss. This was accompanied by increased activation energies, assessed through the Friedman and Kissinger-Akahira-Sunose methods, as well as higher char yields. Conversely, in Epoxy-Xylan, synergistic effects led to reduced activation energy across most α values, resulting in a lower onset temperature and a heightened maximum rate of mixture degradation. Regarding product distribution, all three pseudo-components, particularly lignin, enhanced the selectivity of bisphenol A. Additionally, cellulose and xylan altered the kinetics of N–C and C(N)–C(OH) bond cleavage, reducing the amount and altering the distribution of 2-B-N compounds (compounds featuring two benzene rings and nitrogen). Conversely, the presence of resin reduced the volatiles from cellulose and xylan, promoting phenol-type products and –H and alkylene side chains while diminishing guaiacol-type products and alkyl side chains. Three mechanisms were proposed to elucidate these observed synergistic effects: catalytic effects of –OH groups from biomass pseudo-components, hydrogen exchange or hydrogen bonding between resin-derived nitrogen and biomass-derived oxygen-containing functional groups, and radical reactions. These insights into the co-pyrolysis of biomass and cured epoxy resin can inform the selection of suitable feedstocks for various applications.

Evidence through Thermal Analysis of Retro Diels-Alder Reaction in Model Networks Based on Anthracene Modified Polyester Resins.

The present work is focused on polyester resins obtained from the diglycidyl ether of bisphenol A and anthracene modified 5-maleimidoisophthalic acid. Because the maleimide-anthracene Diels-Alder (DA) adduct is stable at high temperatures, it is considered a good option for high performance polymers. However, the information related to the retroDA reaction for this type of adduct is sometimes incoherent. A detailed thermal study (conventional TGA, HiRes TGA, MTGA, DSC, MDSC) was performed in order to establish whether the rDA reaction can be revealed for this type of anthracene modified polyester resins. The TGA method confirmed the cleavage of the anthracene-maleimide DA adduct, while the DSC demonstrated the presence of anthracene in the system. At high temperatures, unprotected maleimide homopolymerizes and/or reacts with allyl groups according to the -ene reaction. Therefore, the thermal DA reaction is not displayed anymore upon the subsequent cooling, and the glass transition region is registered at a higher temperature range during the second heating. The use of sample-controlled thermal analysis (HiRes TGA) and MTGA improved the TGA result; however, it was not possible to separate the very complex degradation processes that are interconnected.

Effect of an amine-aldehyde condensate modifier on the thermal and mechanical properties of fiber-reinforced epoxy composites

Purpose The manufacture of polymer composites with a lower environmental footprint requires incorporation of sustainably sourced components. In addition, the incorporation of novel components should not compromise the material properties. The purpose of this paper is to demonstrate the use of a synthetic amine functional toluidine acetaldehyde condensate (AFTAC) as a modifier for fiber-reinforced epoxy composites. One of the fiber components was sourced from agricultural byproducts, and glass fiber was used as the fiber component for comparison. Design/methodology/approach The AFTAC condensate was synthesized via an acid-catalyzed reaction between o-toluidine and acetaldehyde. To demonstrate its efficacy as a toughening agent for diglycidyl ether bisphenol A resin composites and for the comparison of reinforcing materials of interest, composites were fabricated using a natural fiber (mat stick) and a synthetic glass fiber as the reinforcing material. A matched metal die technique was used to fabricate the composites. Composites were prepared and their mechanical and thermal properties were evaluated. Findings The inclusion of AFTAC led to an improvement in the mechanical strengths of these composites without any significant deterioration of the thermal stability. It was also observed that the fracture strengths for mat stick fiber-reinforced composites were lower than that of glass fiber-reinforced composites. Originality/value To the best of the authors’ knowledge, the use of the AFTAC modifier as well as incorporation of mat stick fibers in epoxy composites has not been demonstrated previously.

Microencapsulated epoxidized palm oil: A self-healing coating solution

Coatings are susceptible to cracking due to chemical exposure and mechanical forces. To enhance their durability and self-healing properties, microcapsules are utilized. In this study, poly(urea formaldehyde) microcapsules containing epoxidized palm oil as the core material were synthesized and investigated for their self-healing properties in diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The epoxidation reaction of palm oil was carried out by varying reaction times and the molar ratio of hydrogen peroxide to formic acid to achieve an effective oxygen carrier with a high oxirane oxygen content. The formation of epoxide groups was confirmed using Fourier transform infrared spectroscopy (FT-IR) and Fourier transform Nuclear Magnetic Resonance Spectroscopy (NMR). The core-shell structure of the microcapsules was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Pencil hardness and adhesion tests were conducted on the epoxy coatings containing different amounts of microcapsules to evaluate the impact of microcapsules on hardness and adhesion properties. The epoxy coatings with microcapsules demonstrated significant self-healing ability and provided effective anti-corrosive protection. Higher microcapsule contents resulted in improved self-healing performance. Furthermore, the addition of microcapsules at 5 to 15 wt % did not compromise the hardness and adhesion properties of the epoxy coating.

Structural design strategy of biobased propargyl ether-functionalized epoxy monomer to access low viscosity resin with excellent heat resistance and mechanical properties for advanced composite via VARTM

High performance biobased epoxy resin with low viscosity is important for preparing fiber-reinforced polymer composites via vacuum-assisted resin transfer molding (VARTM). Herein, a novel biobased propargyl ether-functionalized epoxy monomer (BPBO) with low viscosity (0.07 Pa·s) was designed and synthesized from renewable eugenol, and then it was combined with methyl nadic anhydride (MNA) to produce a new epoxy system (BPBO/MNA) with excellent properties. The curing behaviors and integrated performances were systematically researched and compared with those of petrochemical-based commercial diglycidyl ether of bisphenol A (DGEBA) type epoxy resin (DGEBA/MNA). BPBO/MNA shows better thermal and mechanical properties than DGEBA/MNA. Specifically, the glass transition temperature (Tg) and the flexural strength of BPBO/MNA resin are as high as 242 °C and 176.2 MPa, about 47 °C and 16.8 % higher than those of DGEBA/MNA resin, respectively, and both of them are the highest among those of eugenol-derived epoxy resins reported so far. The nature behind these outstanding integrated performances is attributed to the unique cross-linked structure of BPBO/MNA that originated from the ring opening polymerization of epoxy with anhydride and the polymerization of aryl propargyl ether groups. Moreover, carbon fiber reinforced composite with attractive performance was developed by taking BPBO/MNA as the resin matrix via VARTM process. This work presents a simple and unique strategy to prepare high performance biobased epoxy resin with low viscosity for advanced composites.

Interplay of curing and thermal degradation in epoxy resins cured with amino acids: Influence of the maximum curing temperature on the network structure, crystal morphology and mechanical properties

AbstractBio‐based alternatives for epoxy resin curing agents are a necessity for fiber reinforced polymer composites to become more sustainable. Here, the precise knowledge about the optimal curing cycle and its influence on the thermoset's mechanical properties are imperative. Therefore, the influence of the maximum curing temperature on the network structure, crystal morphology and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) cured with l‐arginine was investigated with the goal to derive structure–property relationships and a favorable curing cycle. The maximum curing temperature used can be categorized into two regimes: first, the temperature range in which the thermoset reaches complete curing and second, the temperature regime in which the thermoset is fully cured and the thermal degradation starts to diminish its mechanical properties. An optimized curing regimen for achieving high flexural strength accompanied by adequate fracture toughness entails subjecting the material to a curing cycle comprising a duration of 1 h at a temperature of 150°C, followed by an additional 2 h at a temperature of 170°C. This study represents a pioneering effort in optimizing the curing process of amino acid‐cured epoxy resin, specifically focusing on achieving the most favorable mechanical properties as a result.

Thermal and Colorimetric Parameter Evaluation of Thermally Aged Materials: A Study of Diglycidyl Ether of Bisphenol A/Triethylenetetramine System and Fique Fabric-Reinforced Epoxy Composites.

The main modifications of thermal and colorimetric parameters after thermal aging of DGEBA/TETA system (plain epoxy) and fique-fiber woven fabric-reinforced epoxy composites are described. As a preliminary study, thermal analysis was carried out on epoxy matrix composites reinforced with 15, 30, 40 and 50% fique-fiber woven fabric. After this previous analysis, the 40% composite was chosen to be thermally aged, at 170 °C. Three exposure times were considered, namely, 0, 72, 120 and 240 h. Samples were studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and colorimetry analysis. Significant color changes were observed after thermal aging combined with oxidation. It was also found that the thermal behavior of the plain epoxy showed greater resistance after thermal exposure. By contrast, the composites were more sensitive to temperature variations as a result of thermal stresses induced between fique fibers and the epoxy matrix.

Structural reversible adhesives based on thiol-epoxy vitrimers

This work presents a family of functional adhesives based on covalent adaptable networks (CANs). Low-cost and commercially available monomers, including diglycidyl ether of bisphenol A, pentaerythritol tetrakis (3-mercapto propionate) and dipentaerythritol hexakis (3-mercapto propionate), were cured using a base catalyst to produce highly cross-linked materials. The catalyst selection and the study of the curing reaction were performed using differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The catalyst was chosen for better feasibility of industrial production, characterized by short curing times and relatively low temperatures. Thermal stability and thermomechanical properties of the final materials were evaluated through thermogravimetry (TGA) and dynamic mechanical thermal analysis (DMTA), respectively, revealing glass transition temperatures (Tg) higher than 50 °C. Stress relaxation tests were conducted to investigate the vitrimeric behaviour of the polymers, which exhibited an Arrhenius-type dependence of relaxation times on temperature. Importantly, both materials demonstrated impressive creep resistance up to 70 °C, indicating their suitability for use at elevated service temperatures. Tensile and lap-shear tests were also performed, revealing high lap-shear strength values (up to 16 MPa) comparable to those of commercial adhesives. Furthermore, these vitrimers displayed remarkable properties such as shape memory, shape reconfiguration, and self-welding capabilities, underscoring their excellent potential for a wide range of highly demanding applications in industrial production.

Catalyst‐Free, Self‐Healing, and Recyclable Tung Oil‐Based Epoxy Vitrimers with Dynamic Ester Bonds

AbstractLow toughness and nonrecyclability severely limit the applications of traditional thermosets and are not in line with the concept of sustainable development. To solve these problems, water is used as the solvent, and a tung oil‐based tetrafunctional carboxylic acid (TFA) curing agent is obtained through a “one‐pot” method based on previous works. This green synthesis method is suitable for synthesizing tung oil‐based polycarboxylic acid curing agents from various olefin‐containing polyacids. At the same time, the vitrimers (DGEBA‐TFA) are prepared with diglycidyl ether of bisphenol (DGEBA) as the skeleton, and applied to carbon fiber reinforced composites (CFRCs). The tensile strength, tensile modulus and elongation at break of DGEBA‐TFA are 64.62 MPa, 2.55 GPa, and 4.31%, respectively, which are comparable to previous works. Hence, the performance of the vitrimers is not reduced while simplifying the experimental steps. Meanwhile, DGEBA‐TFA exhibits excellent self‐healing, shape memory, and recycling abilities. The vitrimers can be reprocessed without additional catalysts, and the recovery rate remained at 91.3% in the third cycle. DGEBA‐TFA‐CFs exhibite excellent tensile strength. This work solves the problems in previous works and makes TFA more likely to be applied into practical industrial production.

The effects of PPARγ inhibitor on bones and bone marrow fat in aged glucocorticoid-treated female rats

Progressive bone marrow (BM) fat accumulation is a common bone loss characteristic in older populations and glucocorticoid (GC)-induced skeletal destruction that is inversely associated with bone synthesis and directly associated with increased peroxisomal proliferator-activated receptor gamma (PPARγ) expression. PPARγ inhibition is an efficient therapeutic strategy for aged- and GC-related skeletal disorders. This study aimed to evaluate the effect of PPARγ inhibition on aged GC-treated female rats. It was hypothesised that bisphenol A diglycidyl ether (BADGE) could inhibit marrow adiposity and improve osteogenesis by inhibiting PPARγ, thereby preventing GC-induced osteoporosis (GIO). Female Sprague–Dawley rats (n = 32, age = 18 months) were randomly allocated to one of the following groups: (1) control, (2) BADGE (30 mg/kg/day, intraperitoneal), (3) methylprednisolone (MP; 30 mg/kg/day, subcutaneous), and (4) MP + BADGE. After eight weeks of treatment, bone density (BD) and trabecular bone microarchitectures were quantified by micro-computed tomography (CT), and BM adipocytes were quantified by histopathology. Additionally, mRNA and protein expression of adipogenic and osteogenic markers were quantified by reverse transcription-quantitative polymerase chain reaction. Furthermore, serum bone turnover biomarker levels were quantified by enzyme-linked immunosorbent assay. MP treatment led to marrow adipogenesis and bone deterioration. However, rats treated with MP + BADGE showed lower marrow adipogenesis, as indicated by smaller marrow adipocyte diameter, decreased density and area percentages, reduced expression of marrow adipogenic genes and proteins, improved BD and trabecular microarchitectures, increased expression of osteogenic genes and proteins, and higher levels of serum bone formation markers. These results were consistent with the differences observed between control and BADGE mono-treated rats. In conclusion, BADGE treatment attenuates BM adiposity and improves bone formation in aged GC-treated female rats by inhibiting PPARγ. Therefore, PPARγ might be a potential target for treating GIO in older populations.

Tailoring epoxy coating with acetoxime derivative of zinc for advanced anticorrosive performance on mild steel: experimental and computational insights.

In this work, the corrosion inhibitive effect of acetoxime derivative of zinc chloride, (ZnCl2.2HON=C(CH3)2) (ZA), was investigated on mild steel in epoxy/polyamide coating. ZA was used to modify diglycidyl ether of bisphenol A (DGEBA) to yield novel anticorrosive coating (epoxy-ZA) with excellent barrier characteristic. The dispersal of ZA may lead to the formation of Zn-O-C and O-Zn-O linkages in the polymer framework which act as inorganic fillers producing a dense structure of hybrid coating. In electrochemical findings, electrochemical impedance spectroscopy (EIS) and Tafel polarization (TP) indicate higher protection efficiency for epoxy-ZA coatings (99.99 and 99.93 % for EIS and TP, respectively) as compared to others. Using surface analysis and electrochemical data, it was concluded that an inhibition synergy was developed when ZA was taken instead of acetoxime or zinc chloride (ZC) alone in the coating formulation. Fourier transform infrared (FT-IR) was used to investigate epoxy interaction with zinc compounds and scanning electron microscopy (SEM) was used to investigate morphology of the samples. To reinforce the experimental results, reactivity of crosslinked epoxy and epoxy-ZA coatings with metallic surface was also explored using density functional theory (DFT) with basis set B3LYP/6-311G(d,p) and molecular dynamics (MD) methods by using Forcite module. Modification of epoxy with ZA enhances its interaction with steel surface in dry as well as in wet conditions as indicated by the adhesion energy calculated by MD simulations.

Fluid Flow in the Gas Diffusion Layer Using Computational Fluid Dynamics and Microscopy Techniques

The utilization of a proton exchange membrane fuel cell (PEMFC) as an energy provider using hydrogen as a fuel has increased drastically. The reasons are the current limitation of fossil fuel-based devices, pollutants-free, high efficiency, and zero-carbon emission. The life-cycle assessment results of this type of fuel cell have also indicated the lowest contribution to global warming, human health, and resource scarcity in comparison to other types of fuel cells. In this regard, improving the performance of PEMFC is of importance.As an important component of the PEMFC, the gas diffusion layer (GDL) transports the gas reactants to the catalyst layer with the least electrical resistance. The GDL is often made of carbon fibers and should have a surface with good electrical contact and hydrophobic properties to facilitate the water removal. Remaining water in the GDL will result in difficulties during the cold-start and enhances the degradation of this layer. It is believed that the water removal of the GDL has a direct relationship with the capillary pressure, which is strongly linked to the GDL’s microstructure and wettability. However, further investigations can be done once a comprehensive simulation model is developed to monitor the changes in the GDL liquid removal by the effective parameters.In this regard, the Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) has been used to perform three-dimensional cross-section imaging of the GDL. The GDL samples are provided by Freudenberg in which the Microporous layer (MPL) is impregnated into the GDL. The average porosity of this sample is in the range of 75% while having the in-plane gas permeability of 2.4 under a compressive stress of 1 MPa. The utilized resin for FIB-SEM imaging is a mixture of Epoxy embedding medium (diglycidyl ether of bisphenol – A) with two different hardeners DDSA (2-Dodecenylsuccinic anhydride) and MNA (Methylnadic anhydride), which will be mixed with DPM – 30 [2,4,6 – Tris(dimethylaminomethyl)phenol] as the accelerator, all provided by Sigma Aldrich. After the preparation of the resin, 0.4 gr of Cobalt (II) acetylacetonate nanoparticles (supported by Sigma Aldrich) were added to 7.14 ml of the resin to improve the contrast of the images. The samples were impregnated with the resin under vacuum to be pressurized (3 MPa) for 20 minutes, and afterward, heated in an oven at 60℃ for 12 hours. The surfaces for analyses were cut by a diamond wire, polished by abrasive plates down to 0.1 and gold coated (20nm).FIB-SEM acquisition consisted of the polishing of cross-sections with a focused ion beam (LMIS Ga+ source) at 30 keV and 1 nA (Zeiss Crossbeam 540), followed by imaging with an electron beam at acceleration voltages of 1.0, 3.0 kV. Milling and imaging were performed at a working distance of 5.2 mm and stage tilt of 54°, i.e., the coincidence point of the electron and ion beams.Once the three-dimensional cross-sections of the GDL are obtained, the segmentation and reconstruction will be made to provide the needed geometry for fluid flow simulation and to calculate the microstructural properties. Fig. 1 shows the generated structure of the GDL after the segmentation and reconstruction of the cross-section images. The geometry will be then used to characterize the effective parameters of the thermal/water management of the PEMFC. This study can also be a valid reference for future computational fluid dynamic analyses in the GDL using the numerical modeling with the conservative equations or the Lattice Boltzmann modeling (LBM) with the kinetic and particle distribution equations. Keywords : Proton exchange membrane fuel cell (PEMFC); Gas Diffusion Layer (GDL); Focused Ion Beam- Scanning Electron Microscopy (FIB-SEM); Three-dimensional simulation; Lattice Boltzmann method (LBM) Figure 1

Interfacial bond characterization of epoxy adhesives to aluminum alloy and carbon fiber-reinforced polyamide by vibrational spectroscopy

Vibrational spectroscopic technique has been utilized to investigate interfacial bonding chemistry of two epoxy adhesive products, XP0012 and XP5005F, on plasma-treated AA6061 and carbon fiber-reinforced polyamide 66 (CFRP-PA66) surfaces. The change in vibrational peak ratios was measured by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to deduce bonding mechanisms. Both adhesives showed strong crosslinking polymerization of hydroxyl- and amine-initiated epoxy ring opening on AA6061 surface, but on CFRP surface XP0012 formed a simple amide linkage by the reaction of surface hydroxyl groups and nitrile groups of curing agent, and XP5005F formed a crosslinked network by hydroxyl-initiated epoxy ring opening polymerization. The different interfacial bonding formation of two adhesives on CFRP-PA66 surface is attributed to additive effect. Addition of additives to epoxy adhesives (XP5005F) changed the interfacial bonding mechanism on CFRP-PA66 surface, rather forming hydroxyl-initiated epoxy opening crosslinking polymerization than a simple amide bond formation (XP0012). The interfacial bonding chemistry was also proved by addition of bisphenol A (BA) to a simplified model diglycidyl ether of bisphenol A/dicyandiamide (DGEBA/DICY) epoxy system. When BA was added to the model DGEBA/DICY system, epoxy ring gradually decreased on CFRP-PA66 surface, while without BA, DGEBA/DICY showed only decrease in a nitrile peak intensity in ATR-FTIR. The foregoing different types of interfacial chemical bonds at the adhesive/CFRP-PA66 interfaces can affect the lap shear behavior of the joint.

Synthesis of Nanomagnetite/Crosslinked Carboxymethyl kappa Carrageenan Nickel Imprinted Composite

Nickel(II) ions are carcinogenic water pollutants. To increase the accuracy of instrumental analysis of Ni(II) content, several analytical preparation methods have been developed, including solid phase adsorption extraction. The development of magnetic solid phase extraction adsorbents for metal ions is required, to support the application of magnetic solid phase adsorption as a method of separating metal ions in aqueous samples. This research describes the synthesis of Magnetic Solid Phase Extraction adsorbents as Ni(II) ion adsorbents, nano magnetite/carboxymethyl kappa-carrageenan (CMKC) crosslinked bisphenol A diglycidyl ether (BADGE) imprinted Ni(II)-IIP ion composites. This research was carried out in several stages, synthesis and characterization of nano magnetite (NM), synthesis and characterization of CMKC, and synthesis of NM/CMKCNi(II)-IIP adsorbents. The results of the synthesis were analyzed for morphological characteristics, magnetic strength, spectral characteristics, crystallinity, and composition using SEM, FTIR, XRD, and XRF instruments. The adsorption ability of Ni(II) of the adsorbent was tested. Determination of Ni(II) ion content in the sample before and after adsorption was carried out using a flame atomic absorption spectrophotometer (FAAS). Based on the results of spectral character analysis, crystal diffraction patterns, magnetic strength, and morphology, it is confirmed that nano-magnetite has been successfully synthesized. The diameter of the nano magnetite grains is 21.8 nm, the adsorbent NM/CMKCNi(II)-IIP has magnetic properties and wavy surface morphology. The optimum adsorption ability of Ni(II) for the NM/CMKCNi(II)-IIP composite was 2.44 mg Ni(II)/g adsorbent. To evaluate the tendency of the adsorption ability of the adsorbent towards Ni(II) ions in the presence of competitor ions, the adsorption ability of the adsorbent to adsorp Ni(II) ions in samples containing Ni(II) ions, Pb(II) ions and a mixture of Ni(II) ions. and Pb(II) were determined, based on the results of the analysis, the ability of the adsorbent to adsorb Ni(II) ions was higher than the ability of the adsorbent to adsorb Pb(II) ions, in all types of samples.

Development and characterization of DGEBA-APTES-ZrO2 nanocomposite coatings for anti-corrosion and anti-fouling

Tetraethylenetetramine (TETA), 3-aminopropylethoxysilane-treated ZrO2 nanoparticles, and diglycidyl ethers of bisphenol-A (DGEBA) were used to create an epoxy nanocomposite (DGEBA-APTES-ZrO2). The newly synthesized APTES-ZrO2 was evaluated using FTIR, XRD, SEM, AFM, TEM and elemental analysis for structural and compositional analysis. Due to its resilience in acidic, basic and saline conditions, mild steel is crucial in sectors like shipbuilding and the automobile industry. ZrO2 nanoparticles have excellent corrosion resistance. As a result, it is intended to prepare DGEBA-APTES-ZrO2 for a barrier layer that prevents corrosion on mild steel surfaces. FTIR spectroscopy tests provided proof of DGEBA-APTES-ZrO2-coated mild steel’s ability to limit corrosion and microbiological growth. Using salt spray and an electrochemical impedance technique, corrosion inhibition was evaluated. On mild steel surfaces, DGEBA-APTES-ZrO2 nanohybrid coatings demonstrated excellent corrosion prevention and antifouling.

Bio-based amine curing agents prepared from lignin by ring-opening functionalization with cyclic aza-silanes and their curing kinetics investigated for aliphatic and aromatic epoxy species

Bio-based epoxy curing agents from lignin was synthesized by ring-opening reactions of cyclic aza-silane species to obtain lignin-based curing agents with amine hydroxyl equivalent weights up to 68 g/eq. Its cure kinetics was investigated by differential scanning calorimetry in which two representative aromatic and aliphatic epoxy species were employed being diglycidyl ether bisphenol F (DGEBF) and epoxidized soybean oil (ESBO). Utilizing Borchardt and Daniels' method to obtain cure kinetic parameters, the activation energies, Ea, were determined to 101 ± 3 kJ/mol and 71 ± 7 kJ/mol and pre-exponential factors, ln(Z), to 27.6 ± 0.9 s−1 and 13.3 ± 1.7 s−1 respectively for DGEBF and ESBO. The higher pre-exponential factor for DGEBF was attributed to π-π stacking interactions between the aromatic components resulting in overall faster cure kinetics of aromatic-based epoxy species. The lignin-based curing agent retained antioxidative properties which in cured DGEBF thermosets could act as an anti-corrosive agent. This enables the preparation of coatings without the need for leachable additive antioxidants.