A Study on Curing Kinetics of Nano-Phase Modified Epoxy Resin

A liquid metal/carbon nanotubes complex enabling ultra-fast polymerization of super-robust, stretchable adhesive hydrogels for highly sensitive sensor

Carbon nanotubes (CNTs) usually served as conductive and reinforcing nanofillers for making nanocomposites have never been reported to play a role in accelerating fabrication of hydrogels. Herein, we report an important discovery that by involving CNTs and liquid metal (LM) to form a complex (LM@CNTs), multifunctional hydrogels are rapidly prepared from vinyl monomers without heating or adding any initiators and crosslinkers. Study results demonstrate that LM@CNTs not only performs as both initiator and crosslinker for synthesizing hydrogels, but also dramatically reduces the polymerization duration from 3 days to minute levels, compared with that of only LM involved in hydrogel fabrication. Specifically, the complex initiates (<60 s) and crosslinks (<8min) monomers to form the high-performance hydrogels, which significantly reduces energy consumptions. The resulting polyacrylic acid (PAA) hydrogel possesses super stretchability (∼1200 %), high tensile strength (0.96 MPa), outstanding strain sensitivity (Gauge factor = 15.40 at 300-500 % strain), and excellent adhesion to various substrate surfaces. Additionally, the injectable molding performance will benefit the mass production of the hydrogels, which exhibits great potential for applications of wearable flexible sensors. This study provides an environmentally friendly, rapid polymerization, and energy-saving strategy by effectively applying nano-fillers for viable fabrication and application of multifunctional hydrogels.

Dynamic behaviours of epoxy resin thin films during the curing process

Epoxy resin thin films are widely used in applications such as coating materials, insulator films, and adhesives; accordingly, investigations of their physical properties have garnered increasing importance. Although the physical properties of thermoset epoxy thin films are strongly affected by the curing conditions, such as the heating temperature and curing time, the dynamic properties during the curing process have not been studied thoroughly. In this study, we investigated the thermal fluctuations on the surface of epoxy resin thin films using grazing-incidence X-ray photon correlation spectroscopy, to elucidate the dynamic behaviours during the curing process. We thus succeeded in observing the freezing of capillary waves during the thermal curing process. These results are expected to facilitate a deeper understanding of the curing mechanisms of various thin films.

Predicting the Properties of High-Performance Epoxy Resin by Machine Learning Using Molecular Dynamics Simulations

Epoxy resin is an of the most widely used adhesives for various applications owing to its outstanding properties. The performance of epoxy systems varies significantly depending on the composition of the base resin and curing agent. However, there are limitations in exploring numerous formulations of epoxy resins to optimize adhesive properties because of the expense and time-consuming nature of the trial-and-error process. Herein, molecular dynamics (MD) simulations and machine learning (ML) methods were used to overcome these challenges and predict the adhesive properties of epoxy resin. Datasets for diverse epoxy adhesive formulations were constructed by considering the degree of crosslinking, density, free volume, cohesive energy density, modulus, and glass transition temperature. A linear correlation analysis demonstrated that the content of the curing agents, especially dicyandiamide (DICY), had the greatest correlation with the cohesive energy density. Moreover, the content of tetraglycidyl methylene dianiline (TGMDA) had the highest correlation with the modulus, and the content of diglycidyl ether of bisphenol A (DGEBA) had the highest correlation with the glass transition temperature. An optimized artificial neural network (ANN) model was constructed using test sets divided from MD datasets through error and linear regression analyses. The root mean square error (RMSE) and correlation coefficient (R²) showed the potential of each model in predicting epoxy properties, with high linear correlations (0.835–0.986). This technique can be extended for optimizing the composition of other epoxy resin systems.

Curing and Molecular Dynamics Simulation of MXene/Phenolic Epoxy Composites with Different Amine Curing Agent Systems

Herein, the curing kinetics and the glass transition temperature (T_g) of MXene/phenolic epoxy composites with two curing agents, i.e., 4,4-diaminodiphenyl sulfone (DDS) and dicyandiamine (DICY), are systematically investigated using experimental characterization, mathematical modeling and molecular dynamics simulations. The effect of MXene content on an epoxy resin/amine curing agent system is also studied. These results reveal that the MXene/epoxy composites with both curing agent systems conform to the SB(m,n) two-parameter autocatalytic model. The addition of MXene accelerated the curing of the epoxy composite and increased the T_g by about 20 K. In addition, molecular dynamics were used to simulate the T_g of the cross-linked MXene/epoxy composites and to analyze microstructural features such as the free volume fraction (FFV). The simulation results show that the introduction of MXene improves the T_g and FFV of the simulated system. This is because the introduction of MXene restricts the movement of the epoxy/curing agent system. The conclusions are in good agreement with the experimental results.

Cardanol-Derived Epoxy Resins as Biobased Gel Polymer Electrolytes for Potassium-Ion Conduction

In this study, biobased gel polymer electrolyte (GPE) membranes were developed via the esterification reaction of a cardanol-based epoxy resin with glutaric anhydride, succinic anhydride, and hexahydro-4-methylphthalic anhydride. Nonisothermal differential scanning calorimetry was used to assess the optimal curing time and temperature of the formulations, evidencing a process activation energy of ∼65-70 kJ mol-1. A rubbery plateau modulus of 0.65-0.78 MPa and a crosslinking density of 2 × 10-4 mol cm-3 were found through dynamic mechanical analysis. Based on these characteristics, such biobased membranes were tested for applicability as GPEs for potassium-ion batteries (KIBs), showing an excellent electrochemical stability toward potassium metal in the -0.2-5 V voltage range and suitable ionic conductivity (10-3 S cm-1) at room temperature. This study demonstrates the practical viability of these biobased materials as efficient GPEs for the fabrication of KIBs, paving the path to increased sustainability in the field of next-generation battery technologies.

Improving Epoxy Resin Performance Using PPG and MDI by One-Step Modification

The toughening modification of epoxy resin by polyurethane prepolymer (PU) can effectively solve the disadvantage of high brittleness in its application. In this study, a convenient way to toughen epoxy resins was explored, and the monomers PPG and MDI for the synthesis of polyurethane prepolymers were used for a one-step modification of epoxy resins. The test results of viscosity and elongation at break showed that P-M reduced the viscosity of the epoxy resin and improved the toughness. Especially when the content of P-M was 25%, the elongation at the break of the modified EP reached 196.56%. From a thermogravimetric and pyrolysis kinetic analysis, the P-M modification had better thermal stability than the PU modification. These findings have particular implications for the toughening and engineering applications of epoxy resins.

Effect of organic-modified nickel phyllosilicate on the non-isothermal cure kinetics and flame retardancy properties of epoxy composites

In this study, silane agents were employed as organic silicon to synthesize organic-modified nickel phyllosilicates (NiPS), which were then introduced into epoxy resin (EP) to yield composites. The effects of these organic-modified NiPS on the curing behavior and flammability of epoxy composites were then investigated carefully. Though the added NiPS resulted in the initial temperature shifts to high temperature, the whole curing temperature ranges for EP composites became narrow regarding pure EP. Simultaneously, the activation energy of curing was also decreased, implying the lowered energetic barrier during the whole curing process. For all investigated samples, the overall reaction orders varied negligibly, and the predicted curves fitted well with the DSC thermograms. Finally, the positive influence derived from the presence of these organic-modified NiPS on the enhancement of self-extinguishing ability and limited oxygen index were also discussed, and the solid phase flame retardant mechanism was proposed.

The cure behavior of EP/NiPS composites were investigated by non-isothermal DSC. And the curing kinetics for the EP/NiPS composites were described by the autocatalytic equation of the SB model.

Preparation and Properties of 3D Printing Light-Curable Resin Modified with Hyperbranched Polysiloxane

A novel, hyperbranched polysiloxane (HBPSi) is successfully synthesized via hydrolysis using γ-methacryloxypropyl trimethoxysilane (A174) and deionized water, under catalyst-free conditions. Then, for the first time, the HBPSis are used to modify a 3D printing light-curing epoxy resin. Thermogravimetry results showed that the addition of HBPSi improved the heat resistance of the epoxy resin. Experimental results also show that the addition of HBPSi simultaneously improves tensile strength, elongation at break, and impact strength. In particular, a great increase in the toughness of 3D printing light-curing epoxy resin is observed, with 5 wt % HBPSi loading. These results indicate that the HBPSi containg OH- and Si-O-Si can be potentially effective at improving the performance of the 3D printing light-curing epoxy resin. This investigation suggests that the method proposed herein is a new approach to develop the performance of 3D printing light-curing epoxy resin for cutting-edge industries, especially those that simultaneously have outstanding thermal resistance and toughness.

The Curing Kinetics of E-Glass Fiber/Epoxy Resin Prepreg and the Bending Properties of Its Products

The curing kinetics can influence the final macroscopic properties, particularly the three-point bending of the fiber-reinforced composite materials. In this research, the curing kinetics of commercially available glass fiber/epoxy resin prepregs were studied by non-isothermal differential scanning calorimetry (DSC). The curing kinetic parameters were obtained by fitting and the apparent activation energy E_a of the prepreg, the pre-exponent factor, and the reaction order value obtained. A phenomenological nth-order curing reaction kinetic model was established according to Kissinger equation and Crane equation. Furthermore, the optimal curing temperature of the prepregs was obtained by the T-β extrapolation method. A vacuum hot pressing technique was applied to prepare composite laminates. The pre-curing, curing, and post-curing temperatures were 116, 130, and 153 °C respectively. In addition, three-point bending was used to test the specimens’ fracture behavior, and the surface morphology was analyzed. The results show that the differences in the mechanical properties of the samples are relatively small, indicating that the process settings are reasonable.

Photothermal Effect: The Amygdaloidal Nano-Structure Based on Bi2S3 for the Enhanced Degradation of Rhodamine B Under Irradiation by NIR

In recent years the photothermal effect, an auxiliary strategy for increasing the degradation rate of pollutants under irradiation by near-infrared (NIR), has become a research focus. In this study a novel amygdaloidal nanophotocatalyst, Bi2S3, was synthesized by a traditional approach using a hydrothermal process, in which Bi2S3 nanostructures were spread out like a peacock's tail. The produced Bi2S3 photocatalyst exhibited excellent performance in the rapid degradation of Rhodamine B (RB). This proved that the photothermal effect is mainly responsible for the rapid degradation of RB under NIR laser irradiation. Moreover, it was found that the photothermal effect could not degrade the products with NIR radiation in darkness. However, with the support of visible radiation, the photothermal effect of the Bi2S3 photocatalyst enhanced degradation of RB (degradation rate 90% under 1 h). This novel structure exhibited a potential ability for degrading pollution in industry or agriculture.

Heterogeneous dynamics in the curing process of epoxy resins

Epoxy resin is indispensable for modern industry because of its excellent mechanical properties, chemical resistance, and excellent moldability. To date, various methods have been used to investigate the physical properties of the cured product and the kinetics of the curing process, but its microscopic dynamics have been insufficiently studied. In this study, the microscopic dynamics in the curing process of a catalytic epoxy resin were investigated under different temperature conditions utilizing X-ray photon correlation spectroscopy. Our results revealed that the temperature conditions greatly affected the dynamical heterogeneity and cross-linking density of the cured materials. An overview of the microscopic mechanism of the curing process was clearly presented through comparison with the measurement results of other methods, such as 1H-pulse nuclear magnetic resonance spectroscopy. The quantification of such heterogeneous dynamics is particularly useful for optimizing the curing conditions of various materials to improve their physical properties.

The Effect of the Modification of Mica by High-Temperature Mechanochemistry on the Anticorrosion Performance of Epoxy Coatings

Epoxy resin was directly grafted onto the surface of mica powder by high-temperature mechanical ball milling. This method was used to achieve a chemical reaction between the epoxy resin and mica that cannot be carried out under conventional circumstances. The results show that an epoxy resin layer with a thickness of approximately 10 nm formed on the surface of the mica. This modified mica filler exhibited a significant change in its hydrophilic properties. The dispersion of mica and its compatibility with organic coatings also significantly improved. In addition, the modified mica filler was added to the epoxy coating. The improvement of the coating's compactness and toughness is the reason for its anti-corrosion performance enhancement.

Modifying the Microenvironment of Epoxy Resin to Improve the Activity of Immobilized 7α-Hydroxysteroid Dehydrogenases

7α-Hydroxysteroid dehydrogenase (7α-HSDH) is one of the key enzymes in the catalytic reaction of taurochenodeoxycholic acid (TCDCA). To improve the activity of immobilized 7α-HSDH, the microenvironment of immobilized 7α-HSDH was modified with epoxy resin and ethanediamine (EDA). The amino-epoxy support was characterized by Fourier transform infrared (FTIR), Spectrometer elemental analysis (EA), scanning electron microscopy (SEM), contact angle (CA), and Zetasizer. The effects of the immobilization of 7α-HSDH on the amino-epoxy resin and epoxy resin were studied. The results indicated that the relative activity of immobilized 7α-HSDH on the amino-epoxy resin increased by approximately 80%. Meanwhile, the immobilized 7α-HSDH showed favorable thermal stability and operational stability. The thermal stability of immobilized 7α-HSDH increased at temperatures ranging from 15 to 35 °C, while the relative activities of 7α-HSDH immobilized on the amino-epoxy resin and epoxy resin retained 56.4% and 61.0%. After 6 cycles, the residual activities of the 7α-HSDH immobilized on the amino-epoxy resin and epoxy resin were 81.4% and 89.5%, respectively.

Effect of the Aromatic Amine Curing Agent Structure on Properties of Epoxy Resin-Based Syntactic Foams

Epoxy resin is one of the commonly used matrixes of syntactic foams as a buoyancy material, the curing agents of which affect some of the properties for syntactic foams. Therefore, the curing reactions of N,N,N',N'-tetraepoxypropyl-4,4'-diaminodiphenylmethane (AG-80) epoxy resin between 4,4-diaminodiphenyl methane (DDM) and the mixture of m-xylylenediamine and DDM (DDM-m-XDA) systems are studied. The DDM mixed with m-XDA enhances curing reactions with the AG-80 epoxy resin, and the mechanisms of the two curing systems are different through nonisothermal kinetics. Compared with a single curing system, there are some wrinkles on the surface of the AG-80/DDM-m-XDA matrix because of the disordered network. Composited with hollow glass microspheres (HGMs), the more flexible m-XDA structure enhances the interfacial adhesion between the matrix and HGM for syntactic foams. However, the wrinkles in the matrix increase the broken degree of HGMs; especially at HGM contents higher than 55%, the flaw increases the density and water absorption of syntactic foams; meanwhile, it decreases the compressive strength. Therefore, the properties of syntactic foams can be improved by mixing different molecular structure curing agents and the mixture liquid curing agent simplifies the preparation process to some extent.

Thermal Decomposition and Nonisothermal Kinetics of Monoethanolamine Mixed with Various Metal Ions

Ethanolamine is a critical chemical for petrochemical enterprises. When corrosion occurs in pipelines, equipment, and containers in petrochemical enterprises, minute amounts of metal ions are released. In this study, the thermal decomposition and nonisothermal kinetics of monoethanolamine (MEA) and MEA mixed with copper and zinc ions were analyzed using thermogravimetry (TG) and differential scanning calorimetry (DSC). The TG tests revealed that MEA mixed with copper (II) and zinc (II) began thermal decomposition at 75.2 and 60.3 °C, respectively, whereas pure MEA began thermal decomposition at 89.7 °C. Two exothermic peaks were observed in the DSC curves for MEA mixed with copper (II) and zinc (II), and thermokinetic parameters were obtained from DSC data. The apparent activation energy (E_a) of each stage was calculated using several nonisothermal kinetic methods, namely the ASTM E698, Kissinger–Akahira–Sunose, Starink, and Flynn–Wall–Ozawa methods. The E_a of pure MEA was 28.7 ± 2.5 kJ/mol, whereas that of the copper and zinc mixtures were 80.5 ± 1.1 and 46.8 ±1.7 kJ/mol, respectively. The results can be used to improve the intrinsic safety of storage tanks and petrochemical plants.

A Research on Preparation and Application of the Monolithic Catalyst with Interconnecting Pore Structure

In recent years, the monolithic material has been developed increasingly in the high performance liquid phase field, and it could also be applied in the field of catalyst, as a monolithic catalyst carrier, since it has a large specific surface area, and could be customized based on the mould. The monolithic catalyst is characterized with many advantages such as low bed pressure, high physical efficiency and small amplification effect. The most impotant part refers to the preparation of copper-based catalyst. The impregnation method is used to produce CuO-ZnO monolithic catalyst and CuO-ZnO-ZrO₂ monolithic catalyst with the prepared monolithic silica-alumina carrier. The fixed bed microreactor is used to investigate the effect of copper-based catalyst on the process in which carbon dioxide is used to produce methanol through hydrogenation. The metal salt is added into the sol-gel process, which could form the M-O-Si bond, thus make the metal-containing catalytic material obtain good mechanical strength, and make it possible to be introduced into the acidic center generally. The metal-containing catalytic material carrier also has macropores and mesopores. The presence of large pores could make the molecular mass transfer more effective, while the presence of mesopores could increase the specific surface area of the material. In this paper, the experimental study has been conducted on the production of methanol through hydrogenation of CO₂ under different catalysts, to mainly investigate the effect of catalysts with different catalytic performance on the reaction.

Effects of UV for Cycloaliphatic Epoxy Resin via Thermokinetic Models, Novel Calorimetric Technology, and Thermogravimetric Analysis

The cycloaliphatic epoxy resin selected for this study was 3,4-epoxycyclohexane methyl-3′4′-epoxycyclohexyl-carboxylate (EEC). Epoxy resin has numerous applications, such as varnishes, tires, and electronic materials. However, the extensive used of chlorofluorocarbon (CFC) compounds in the last century has resulted in the formation of a hole in the ozone layer. As a consequence, solar radiation is intensifying gradually; therefore, continuous irradiation by sunlight should be avoided. The results of solar radiation can exacerbate the deterioration and photolysis of compounds. Through thermogravimetry and differential scanning calorimetry, the apparent onset temperature of EEC and EEC was analyzed under UV radiation for different durations. Thermokinetic data were used to determine the parameters of thermal decomposition characteristics through simulation to assess the reaction of EEC and EEC under UV radiation for different durations. The goal of the study was to establish the parameters of thermal decomposition characteristics for the effects of UV on EEC, as well as the probability of severity of thermal catastrophe.