Epoxy Moiety Research Articles

Fabrication of Hybrid Epoxy Composites (Joint Compound Adhesive) for Aluminum Substrate Applications and Their Evaluation for Mechanical Properties.

This research endeavor deals with the development of an epoxy hybrid nanocomposite using aliphatic diglycidyl ether of a bisphenol A (DGEBA) epoxy matrix. The formulation used the stoichiometric ratio of the curing agent and incorporated nanopigments such as zirconium and silica, along with other microfillers. We incorporated Zr and SiO2 nanoparticles and various other additives in the epoxy matrix and ensured homogeneous dispersion by using sonication methodology along with silane as a coupling agent. Aluminum molds were utilized to fabricate dumbbell-shaped ASTM standard samples for the testing of mechanical properties. The adhesive properties were evaluated through standard lap shear tests. Fourier transform infrared spectroscopy was utilized to analyze the cross-linking reaction of the epoxy moiety and the polyamidoamine adduct curing agent. Further characterization using field emission scanning electron microscopy, energy-dispersive spectroscopy, and high-resolution transmission electron microscopy confirmed the presence and uniform dispersion of the fillers and nanopigments. The results showed good enhancements in ultimate tensile strength, yield strength, and elastic modulus of 95.3, 162.1, and 425.4%, respectively, compared to formulations using only SiO2. The addition of ZrO2 and SiO2, along with various microfillers, such as talc and aluminum silicate, led to significant improvements in the mechanical properties. This study demonstrates the synergistic efficiency of combining SiO2 and ZrO2 along with microfillers, such as talc and aluminum silicate, in epoxy resin for diverse applications in the construction industry, where mechanical strength and substrate adhesion are crucial.

Biotransformation of Patchouli Alcohol by Cladosporium cladosporioides and the Anti-Influenza Virus Activities of Biotransformation Products.

The biotransformation of patchouli alcohol by Cladosporium cladosporioides afforded 31 products, including 21 new ones (1-3, 5, 6, 8-14, and 17-25). Their structures were determined by extensive spectroscopic data analysis (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, ROESY, and HRESIMS), and the absolute configuration of compounds 1, 2, 8, 9, and 17 was determined by single-crystal X-ray diffraction using Cu Kα radiation. Structurally, compounds 21-24 were patchoulol-type norsesquiterpenoids without Me-12. Among them, a Δ3(4) double bond existed in compounds 21 and 22; a three-membered ring was formed between C-4, C-5, and C-6 in compound 23; an epoxy moiety appeared between C-3 and C-4 in compound 24. Furthermore, the biotransformation products 9, 10, 12, and 25 showed potent anti-influenza virus activity with EC50 values of 2.11, 7.94, 20.87, and 3.45 μM, respectively.

Dual cross‐linking of XNBR latex with epoxy‐functional calcium silicate particles for the production of accelerator‐free medical gloves

AbstractIn this work, an innovative dual cross‐linking strategy for carboxylated nitrile butadiene rubber (XNBR) latex using epoxy‐modified calcium silicate particles is presented. In their role as dual cross‐linker, the particles are able to form covalent bonds (nucleophilic ring opening of epoxy moieties) as well as ionic cross‐links (calcium ions of the inorganic core) across the carboxylic acid groups of the rubber. To characterize the curing efficiency, thin elastomer films are prepared by using a conventional coagulant dipping process and their cross‐link densities, curing kinetics, and tensile properties are investigated as a function of the concentration of the cross‐linker and curing time. The results show that latex films containing 5 phr of epoxy‐functional particles give the highest tensile strength, which is further improved by pre‐vulcanizing the liquid latex compound at 60°C for 30 min. The latex formulations are stable over 3 days and the pre‐cured films exhibit a high resistance against gamma sterilization and subsequent accelerated aging. Moreover, sterile films do not cause any skin irritation or skin sensitization reactions, showing the high potential of epoxy‐functional particles in the production of accelerator‐free hypoallergenic gloves.

Cytotoxic Dammarane-Type Triterpenoids from <i>Aglaia cucullata</i> Peel Fruit

Four triterpenoids, known as dammarane-type, dammaradienone (1), 20(S),25-epoxy-5α-dammar-20-en-3-one (2), 20(S)-5α-dammar-24-en-3α,20-diol-3-acetate (3) and 3α-acetyl-20S,24S-epoxy-25-hydroxydammarane (4), were isolated from Aglaia cucullata peel fruit. The structures of isolated compounds were identified based on their HR-TOFMS data and extensive NMR spectroscopic analysis, as well as compared with literature data. Compounds 1-4 were assessed for cytotoxic effects against HeLa cervical and B16-F10 melanoma skin cancer cells. All compounds showed moderate to weak activity against B16-F10 cancer cells, while compound 2 exhibited the strongest activity against HeLa cancer cells with IC50 of 7.10 µg/mL indicating that the existence of an epoxy moiety at the side chain increases the cytotoxicity to HeLa cells.

Reference-free quantitative mass spectrometry in the presence of nonlinear distortion caused by in situ chemical reactions among constituents.

Materials performance is primarily influenced by chemical composition, making compositional analysis (CA) essential in materials science. Traditional quantitative mass spectrometry, which deconvolutes analyte spectra into reference spectra, struggles with reactive systems where spectral variations occur, such as peak shifts and new peak emergences. Additionally, obtaining reference spectra for all pure constituents is often impractical. To address these challenges, I propose nonlinear reference-free quantitative mass spectrometry (NL-RQMS). This method simultaneously determines composition, reference spectra, and nonlinear interaction effects directly from a spectral dataset of mixtures, eliminating the need for prior reference spectra. In a benchmark test on ternary reactive polymers of epoxy and amines, NL-RQMS inferred compositions with an error margin of just 3 wt%, significantly outperforming the 6 wt% error margin of linear RQMS. The inferred interaction terms clearly indicate in situ reactions between epoxy and amine moieties. This framework enables accurate compositional analysis without prior knowledge of the constituents, even in systems with interactive components, and holds significant potential for applications such as grading recycled plastics, where pristine materials, degradation compounds, and stabilizers interact complexly, causing nonlinear spectral distortions.

Chemistry of new polyfluorinated oxiranyl anions and epoxy silanes

The reaction of partially fluorinated epoxides with strong, hindered bases in the presence of electrophiles resulted in functionalization of the epoxy ring. For example, the reaction of hexafluoroisobutene epoxide with LDA and trimethyl- or triethychlorosilanes at low temperature led to the formation of the corresponding epoxy silanes. In the case of the E- and Z-epoxides of 1,1,1,3,3,3-hexafluorobutene-2, the deprotonation step can be successfully carried out using i-PrMgCl.LiCl (Turbo Grignard reagent), and the reaction with chlorosilanes can be carried out at ambient temperature, which significantly simplifies the synthetic protocol. The process was found to be stereospecific, proceeding with complete retention of configuration of the epoxide ring and giving access to pure E- or Z-isomers of the corresponding epoxy silanes. Using this protocol, the corresponding epoxy silanes were also prepared from the epoxides of E-3,3,3,1-tetrafluoropropene-1 and 3,3,3-trifluoropropene-1.The new silanes were demonstrated to be convenient reagents for the transfer of a fluorinated epoxy moiety to carbonyl compounds under fluoride anion catalysis. This process was shown to proceed with complete retention of the geometry of the epoxy ring.

Investigation on the effect of castor‐oil based bio‐resins on mechanical, visco‐elastic, and water diffusion properties of flax fiber reinforced epoxy composites

AbstractDue to the depletion of petro‐based sources and environmental consciousness, researchers are striving to replace synthetic fibers and resins in composites with bio‐sourced ones without compromising their properties. In this regard, the present study investigates the effect of partially replacing epoxy moieties with castor oil based bio‐resins on various properties of epoxy resin and its flax fiber reinforced composite system to achieve sustainable materials, thereby encouraging the bio‐based theme. Base‐catalyzed transesterification was used to synthesize epoxy methyl ricinoleate (EMR) as a low viscous reactive green monomer derived from epoxidized castor oil (ECO). The influence of both ECO and EMR bio‐resin on various mechanical, thermo‐mechanical properties, free mode vibration, and water absorption of epoxy and its composites were studied. The composition with 20% of ECO and EMR was optimized based on stiffness‐toughness balance. The inclusion of 20% EMR significantly escalated the tensile, impact, and fracture toughness properties of epoxy composites by 6.45%, 12.8%, and 14.2%, respectively. The strong fiber‐matrix interface was confirmed by increased pullout adhesion by 21% and 35.1% due to the addition of ECO and EMR, respectively. Dynamic mechanical analyzer revealed a 12% higher storage modulus for EMR modified composites than ECO counterparts. Scanning electron microscope morphology revealed superior interfacial adhesion between fiber and matrix in case of EMR modified bio‐composite, which resulted in a lower water diffusion coefficient than ECO modified bio‐composite. These results showed that the 20% EMR customized epoxy composite is dimensionally stable with improved mechanical properties and may act as a green alternative to petro‐sourced epoxy composites in automotive and semistructural applications.Highlights Effects of castor oil based bio‐resins on epoxy composites are studied. Composites with significant bio‐content (~50 wt%) are developed. EMR modified epoxy composites exhibited improved mechanical properties. A strong fiber‐matrix interface was confirmed by increased pullout adhesion. Reduction in pot life of epoxy was observed on adding ECO and EMR.

Alternative Construction of the Core of Lindenane Sesquiterpenoid

Comprehensive SummaryAlternative synthetic routes toward the tricyclic core of lindenane sesquiterpenoid are presented herein. The route A features an asymmetric organocatalysis enabling desymmetric silylation of diol to establish the desired tertiary alcohol, while the route B consists of an acetate ring opening of chiral epoxy moiety. The common intermediate (16) in both routes can give rise to the core of lindenane sesquiterpenoid via an intramolecular cyclopropanation.

Microwave-Assisted Functionalization of Multi-Walled Carbon Nanotubes for Biosensor and Drug Delivery Applications

Microwave-assisted synthetic methods have emerged as a popular technique for surface modification and the functionalization of multi-walled carbon nanotubes (MWCNTs) for diverse drug delivery applications. Microwave-induced functionalization of MWCNTs provides a high functionalization and requires less time than conventional techniques. Microwave methods are simple, fast, and effective for the covalent and noncovalent conjugation of MWCNTs with various biomolecules and polymers. The present review focuses on the synthetic and drug delivery applications of microwave irradiation techniques (MITs) for the functionalization of MWCNTs, using amino acids and other molecular frameworks containing amino groups, vitamins, proteins, epoxy moieties, metal nanoparticles, and polymers.

Synthesis of Open‐Cage Fullerenes Containing a H‐Bond between the Encapsulated Water Molecule and the Amide Moiety on the Rim of the Orifice

AbstractFurther hydrolysis of an open‐cage fullerene derivative with an epoxy moiety on the rim of the orifice led to the formation of a new open‐cage fullerene with a 17‐membered orifice and an amide group directly above the orifice. The water encapsulation ratio in the new open‐cage compound reached 100 % as a result of heating with water at 80 °C. The amide group above the orifice completely blocks the opening and forms H‐bond with the trapped water molecule. Single crystal X‐ray structure shows that the bond length between the trapped water oxygen and the amide oxygen is 2.859 Å. The H‐bond energy is about −3.83 kcal/mol as shown by theoretical calculation.

Non-sulfated steroidal glycosides cistoindosides from marine ‘old woman octopus’ Cistopus indicus attenuate pro-inflammatory lipoxygenase

Two non-sulfated steroidal glycosides, cistoindosides A-B were isolated from organic extract of the marine ‘old woman octopus’ Cistopus indicus (family Octopodidae). Their structures were characterized as 3β-acteoxy-23β-hydroxy-cholesta-9-ene-β-D-xylopyranoside (cistoindoside A) and 22,23-epoxy-3β-hydroxy-cholesta-5-ene-β-D-4'-O-acetoxy-xylopyranoside (cistoindoside B). Cistoindoside B, glycosylated with β-D-4'-O-acetoxy-xylopyranoside in conjunction with epoxy moieties displayed superior anti-inflammatory properties as acknowledged by its promising 5-lipoxygenase attenuation potential (IC50 2.11 µM) than the 5-lipoxygenase inhibitor drug zileuton (IC50 3.76 µM). The anti-inflammatory properties were corroborated by the promising antioxidant activities (IC50 ∼ 1.0–1.5 mM) of these steroid glycosides. Sizeably greater electronic properties, balanced hydrophobic-lipophilic properties (log POW ∼ 4.0) and comparatively lower steric factors were directly proportional to their bioactivities. Molecular simulation studies in the active sites of 5-lipoxygenase displaying lesser binding energies and inhibition constant (Ki) of cistoindoside B could be correlated with anti-inflammatory properties. Cistoindosides could be projected for their utilization as potential bioactive leads in functional food and pharmaceutical applications.

Glycidate as a High-Strength Epoxy Adhesive Curable with Amine under Ambient Conditions.

This paper reports that glycidates bearing epoxy moieties with adjacent ester can be cured with diethylenetriamine (DETA) under mild conditions and exhibit high adhesiveness. Curing of bifunctional glycidates with DETA gave cross-linked products. The curing started at a lower temperature (7 °C) than the analogous glycidyl ether (27 °C), while the rate of the curing was slower due to the lower activation energy (Ea = 57 kJ/g) and exothermicity (ΔH = 58 J/g) as confirmed by DSC analysis. The curing system of neopentyl glycol diglycidate and DETA effectively adhered aluminum plates by curing at 25 °C, and the strength was more than five times higher than the curing with analogous glycidyl ether. The higher adhesive strength under curing of ambient conditions and facile preparation of monomers are the significant advantages of this curing.

Effect of Functional Group on the Catalytic Activity of Lipase B from Candida antarctica Immobilized in a Silica-Reinforced Pluronic F127/α-Cyclodextrin Hydrogel

Surface modification plays a key role in the fabrication of highly active and stable enzymatic nanoreactors. In this study, we report for the first time the effect of various functional groups (epoxy, amine, trimethyl, and hexadecyl) on the catalytic performance of lipase B from Candida antarctica (CALB) incorporated within a monolithic supramolecular hydrogel with multiscale pore architecture. The supramolecular hydrogel formed by host-guest interactions between α-cyclodextrin (α-CD) and Pluronic F127 was first silicified to provide a hierarchically porous material whose surface was further modified with different organosilanes permitting both covalent anchoring and interfacial activation of CALB. The catalytic activity of nanoreactors was evaluated in the liquid phase cascade oxidation of 2,5-diformylfuran (DFF) to 2,5-furandicarboxylic acid (FDCA) under mild conditions. Results showed that high FDCA yields and high efficiency conversion of DFF could be correlated with the ability of epoxy and amine moieties to keep CALB attached to the carrier, while the trimethyl and hexadecyl groups could provide a suitable hydrophobic-hydrophilic interface for the interfacial activation of lipase. Cationic cross-linked β-CD was also evaluated as an enzyme-stabilizing agent and was found to provide beneficial effects in the operational stability of the biocatalyst. These supramolecular silicified hydrogel monoliths with hierarchical porosity may be used as promising nanoreactors to provide easier enzyme recovery in other biocatalytic continuous flow processes.

Surfaces with Adjustable Features-Effective and Durable Materials for Water Desalination.

Materials based on PVDF with desirable and controllable features were successfully developed. The chemistry and roughness were adjusted to produce membranes with improved transport and separation properties. Membranes were activated using the novel piranha approach to generate OH-rich surfaces, and finally furnished with epoxy and long-alkyl moieties via stable covalent attachment. The comprehensive materials characterization provided a broad spectrum of data, including morphology, textural, thermal properties, and wettability features. The defined materials were tested in the air-gap membrane distillation process for desalination, and improvement compared with pristine PVDF was observed. An outstanding behavior was found for the PVDF sample equipped with long-alkyl chains. The generated membrane showed an enhancement in the transport of 58–62% compared to pristine. A relatively high contact angle of 148° was achieved with a 560 nm roughness, producing a highly hydrophobic material. On the other hand, it was possible to tone the hydrophobicity and significantly reduce adhesion work. All materials were highly stable during the long-lasting separation process and were characterized by excellent effectiveness in water desalination.

Performance tuning of glass fiber/epoxy composites through interfacial modification upon integrating with dendrimer functionalized graphene oxide

AbstractIn this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoamine (PAM) dendrimer functionalized graphene oxide (GO) into epoxy matrix. Two different composites each containing varying loading fraction (0.5, 1.0, and 1.5 wt%) of GO and GO‐PAM were fabricated via hot press processing. Composites were evaluated for interlaminar shear strength (ILSS), dynamic mechanical properties and thermal conductivity. The inclusion of 1.5 wt% GO‐PAM resulted ~57.3%, ~42.7%, and ~54% enhancement in ILSS, storage modulus and thermal conductivity, respectively. Almost, ~71% reduction in coefficient of thermal expansion was also observed at same GO‐PAM loading. Moreover, higher glass transition temperature was observed with GO‐PAM addition. GO‐PAM substantially improved fiber/matrix interfacial adhesion, which was witnessed through scanning electron microscopy. The enhanced thermo‐mechanical performance was attributed to interfacial covalent interactions engendered by ring opening reaction between epoxy and amine moieties of PAM dendrimers. These multiscale composites with extraordinary functional properties can outperform conventional counterparts with improved reliability and performance.

The influence of temperature on the nature and stability of surface-oxides formed by oxidation of char

A coal char has been oxidized isothermally at temperatures comprised between 300 and 1073 K. The pre-oxidized chars have been subjected to Temperature Programmed Desorption (TPD) and to core-level high-resolution X-ray photoelectron spectroscopy (XPS) analysis using Synchrotron radiation to infer the nature of the carbon oxides that populate the surface and their evolution throughout thermochemical processing. For low oxygen coverages and mild oxidation temperatures the prevailing carbon-oxygen moieties are epoxy. Raising the oxidation temperature up to ~723K the edge carbon oxygen complexes (ether-hydroxyl and carbonyl-carboxyl) increase. The amounts of CO + CO2 desorbed during TPD also increase with temperature and duration of oxidation for relatively mild oxidative treatments (temperature below ~723K). Upon further increase of the oxidation temperature the amount of CO + CO2 decrease and the ratio of CO/CO2 increases remarkably. Altogether, results suggest the existence of a strong link between a remarkable shift of surface oxides from epoxy to ether/carbonyl and the desorption of CO and CO2. Moreover, the CO/CO2 ratio during desorption can be well correlated with the relative abundance and stability of epoxy moieties with respect to the “edge” oxides. Results are analyzed in the frame of a semi-lumped kinetic model of carbon oxidation with a focus on the role and nature of surface oxides as intermediates in carbon gasification reactions.

Graphitic nanoparticles functionalized with epoxy moiety for enhancing the mechanical performance of hybrid carbon fiber reinforced polymer laminated composites

AbstractExceptional properties and unique structural features of graphene make it a successful secondary reinforcing agent for the enhancement of mechanical performance of hybrid carbon fiber reinforced polymer (CFRP) composites. In this study, graphitic nanoparticles (GrNPs) were functionalized with the epoxy moieties through the traditional silanization method and an innovative approach of grafting with epichlorohydrin and then reinforced in epoxy system to prepare nanocomposites and hybrid CFRP laminated composites. The morphological, structural, and thermal investigation revealed the successful functionalization of GrNPs. The tensile strengths of the nanocomposites were found significantly enhanced by ~36% due to incorporation of silanized GrNPs and ~30% due to incorporation of epichlorohydrin grafted GrNPs compared to the neat epoxy. The tensile strengths of the resulting CFRP composites reinforced with silanized and epichlorohydrin grafted GrNPs showed ~37% and ~36% improvements, respectively, as compared to the control sample. Comparing the results of silanized and epichlorohydrin grafted GrNPs nanocomposites, it has been found that silanization has better potential to improve the mechanical performance of the hybrid CFRP composites as compared to epichlorohydrin grafting.

Characterization of surface-oxides on char under periodically changing oxidation/desorption conditions

A novel experimental method based on periodic swinging of oxidation/desorption reaction stages is used to investigate the formation and release of surface oxides on carbon under mild oxidation conditions. The chemical nature of the carbon-oxygen complex and the key mechanistic features of the interaction between solid carbon and oxygen are assessed by continuous monitoring of CO/CO2 release during the experiments and by probing - via XPS - the chemical nature of oxygen moieties at different stages of the experiments. Sub-bituminous char is used as carbon substrate. The proposed technique turns out to be a simple though effective method to assess the nature and extent of surface oxides formed under different reaction conditions. Results show that oxygen is extensively chemisorbed on carbon as epoxy moieties below ~750 K. At higher temperatures, isomerization into “edge” oxides (ether-hydroxyl and carbonyl-carboxyl functionalities) takes place, followed by oxide decomposition and desorption as CO and CO2. Estimates of the oxygen chemisorption rate as a function of temperature are given. The study provides new insights into the extent and chemical nature of surface oxides on carbons, that represent one key to their successful application in several areas of energy conversion and storage. Oxides affect surface physico-chemical (polarity, wettability) and electrical (capacitance, resistivity) properties, relevant to application of carbons in batteries, supercapacitors and fuel cells. Moreover, understanding surface oxides on carbon is helpful in designing novel concepts of energy conversion from carbon through chemical looping, transient operation of stationary combustors, synthesis of carbon-based catalysts, beneficiation of ash.

Mechanical and thermal properties of carbon fiber reinforced composite with silanized graphene as nano-inclusions

The use of nanofillers to enhance the properties of fiber reinforced composites is limited due to the adverse effect on mechanical properties caused by agglomeration of these nanofillers in the matrix materials. In this study, graphene nanoflakes were functionalized with silane moiety to improve its dispersion, stability and bond strengths in the polymer matrices of the carbon fiber reinforced composites. Wet layup process was applied to incorporate graphene nanocomposites into the dry carbon fibers to make composite panels following the curing cycle of the epoxy and hardener. The impacts of the functionalized graphene on the mechanical and thermal properties of carbon reinforced composite were investigated in detail by tensile test, differential scanning calorimetry, dynamic mechanical analysis and scanning electron microscopy (SEM) analysis. It was observed that nanocomposites with 0.5 wt% silanized graphene exhibited maximum tensile strength and modulus of elasticity, indicating that 0.50 wt% silane functionalized graphene was the optimum nanofiller composition amongst the three different compositions investigated. The nanocomposites with 0.25 wt% and 0.50 wt% nanofillers showed improved ductility compared to the control sample. Based on the SEM studies on the crack zones, major morphological changes were observed after the salinization process. The interfacial interaction between epoxy and silane moiety of the graphene and reduction in the tendency to agglomerate could account for the improved properties of the nanocomposite observed here. Nanocomposites with silanized graphene showed overall higher glass transition temperature (Tg) and tensile strength than those with pristine graphene and control samples.

Photosensitized Production of Singlet Oxygen via C60 Fullerene Covalently Attached to Functionalized Silica-coated Stainless-Steel Mesh: Remote Bacterial and Viral Inactivation

This study demonstrates the capability of a C60-based sensitizer to remotely inactivate bacteria and viruses in air. The nucleophilic addition of amine groups attached to SiO2 particles (used as free-standing support or as hosts electrosprayed on a stainless-steel mesh) to the double bonds of C60 led to the production of recyclable sensitizers. The high-yield production of singlet oxygen (1O2) from the immobilized C60 was established by studying the effects of 1O2 quenchers and enhancer on furfuryl alcohol (FFA) oxidation efficiency and wavelength-dependent FFA decay kinetics. We monitored the inactivation rates of Staphylococcus aureus and MS-2 bacteriophage in petri dishes at predetermined distances from the 1O2 source and identified the probability of remote microbial inactivation via 1O2, which occurred up to 10-15 cm from the source. This result accorded with epoxy moiety occurrence as an indication of singlet oxygenation in the Fourier Transform-Infrared spectra of cis-polybutadiene in remote positions.