Prepare Epoxy Resin Research Articles

Preparation and performance comparison of low‐dielectric epoxy resins cured by naphthalene‐ and phenyl‐based active esters

AbstractThe poor dielectric properties of epoxy resins limit their application in microelectronics, and active ester curing agent is an effective means to enhance the dielectric properties of epoxy resins. However, the phenyl active ester curing resins nowadays have the problem of low mechanical properties. In this work, a novel naphthalene‐based active ester‐cured resveratrol epoxy resin system (REP/NDA) was prepared for the first time. Compared with the phenyl‐active ester‐cured epoxy resin (REP/PDA), the naphthyl‐active ester prepared epoxy resin has obvious advantages in mechanical properties. The experimental results indicated a tensile strength measurement for REP/NDA at 91.9 MPa, the tensile strength of REP/PDA was 65.3 MPa, and the tensile strength of REP/NDA was 141% of that of REP/PDA. The prepared REP/NDA epoxy resin exhibits favorable dielectric properties, evidenced by a dielectric constant of 3.02 at 10 MHz and a dielectric loss of 0.0042, very good thermal stability (T5% of 379°C), excellent water absorption (only 0.49% for 7 days from 2 to 8°C) and good dimensional stability (coefficient of thermal expansion below Tg of 77 ppm). The first synthesis of naphthalene‐based active ester curing agent offers a reference for creating new low dielectric epoxy resin materials that work out exceptionally.

Ultra-high cross-linked active ester-cured epoxy resins: Side group cross-linking for performance enhancement

Active ester hardeners are a unique class of epoxy hardeners that undergo a curing reaction without generating secondary hydroxyl groups. This characteristic enables the production of low dielectric and low moisture absorption epoxy resins. In this study, two active ester hardeners, bisphenol A diisobutyrate (DIB) and bisphenol A dimethacrylate (DMA), were used to prepare epoxy resins by reacting with a resveratrol-based epoxy monomer (REP). By cross-linking the double bonds in the resin (using dicumyl peroxide, DCP), the properties of the resin can be dramatically changed. Among the resins prepared, REP/DMA/DCP exhibited the highest cross-linking density, approximately 48 times that of REP/DIB. Its storage modulus at 300 °C remained at 600 MPa, indicating an equivalent glass transition temperature (Tg) higher than 300 °C. Additionally, the cross-linking of the ester side groups increased the initial degradation temperature by 12–13 °C, reaching 395–396 °C. Regarding the coefficient of thermal expansion (CTE), the cross-linking of ester side groups had no significant effect on the CTE in the glassy state. However, it drastically reduced the CTE above the glass transition temperature. The average CTE (30–300 °C) of REP/DMA/DCP was only 106 ppm/°C. Furthermore, the cross-linking of the ester side groups appeared to reduce the dielectric constant but increased the dielectric loss and the water absorption rate. Nevertheless, REP/DMA/DCP's dielectric constant at 10 MHz of 3.07, dielectric loss of 0.01, and saturated water absorption of 0.77 wt% remain in the low range.

POSS/EHTPB synergistically toughened epoxy resin for cryogenic application

The high brittleness of epoxy resin at cryogenic temperature restricts their wide application in cryogenic engineering. In this study, polyhedral oligomeric silsesquioxane (POSS) with -Si-O-Si- molecular chains were synthesized, and the mechanical properties of diglycidyl ether of bisphenol A (E51 epoxy resin) were significantly enhanced at room temperature (RT) by incorporating a 4% POSS and curing agent 4,4′-diamino-diphenylmethane (DDM) as the E51/POSS/DDM resin system. Subsequently, by adding different contents of epoxidation hydroxyl-terminated polybutadiene (EHTPB) into the E51/POSS/DDM resin system, the EHTPB-E51/POSS/DDM resin system was prepared. The investigation into the impact of EHTPB content on the mechanical properties of EHTPB-E51/POSS/DDM resin system at room temperature (RT) revealed that EHTPB-E51/POSS/DDM resin system with 10% EHTPB exhibited the most favorable results. Specifically, the elongation at break, flexural strength, and critical stress intensity factor (KIC) were measured to be 6.82%, 143.75 MPa, and 1.83 MPa m1/2, respectively. These values demonstrated a notable improvement of 53.3%, 26.9%, and 86.7% compared to those for the E51/DDM resin system. Concurrently, at 77 K, the elongation at break and critical stress intensity factor (KIC) increased by 37.8% and 73.5%, respectively. The toughening mechanism of the prepared EHTPB-E51/POSS/DDM resin system was further explored through resin-curing cross-linking simulation networks and SEM images of the fracture surface of resin samples. The study of EHTPB and POSS synergistically toughened epoxy resin provided a new efficient method to prepare epoxy resins with high toughness at low temperatures.

Adsorption of Congo Red by chitosan porous beads reinforced with epoxy resin

This study prepared epoxy resin reinforced porous beads (CERBs) by crosslinking a water-soluble epoxy monomer, 1,4-butanediol diglycidyl ether (BDE), with chitosan (CS) using isophorone diamine (IPD) as a crosslinking agent.

Enhanced radiation shielding performance of epoxy resin composites with Sb2O3 and Al2O3 additives

We prepared epoxy resin composites containing Sb2O3 and Al2O3 for radiation shielding applications, such as in the fields of nuclear medicine and medical radiation for both occupational and public radiation protection. The linear attenuation coefficient (LAC) was measured by a collimated gamma radiation technique with the use of a NaI(Tl) scintillation crystal detector. The density of the prepared SbAl composites is determined to be between 1.31 and 1.48 g/cm3, which is higher than that of pure epoxy. We reported the impact of Al2O3 on the radiation shielding performance of the prepared composites. At 0.059 MeV, we found that the linear attenuation coefficient (LAC) increases from 1.45 to 1.64 cm−1 when the Al2O3 changes from 5 to 20 w.t.%. We found that at 0.059 MeV, the Al2O3 has a notable impact on the LAC and on the other parameters such as the half value layer. At 0.662 MeV, we found that the Al2O3 has a small influence on the LAC and HVL, where the LAC increases only from 0.0978 to 0.1071 cm−1. Moreover, the HVL at 0.662 MeV is in the range of 6.47–7.08 cm. From the HVL results, we found that epoxy resin composites that are thinner than 6 cm and include 15% Sb2O3 and various quantities of Al2O3 (up to 20%) are not appropriate for use in applications that demand for attenuating radiation with an energy lower than 0.662 MeV. The study's findings could be useful in optimizing shielding materials used to help protect personnel and patients in facilities using medical radiation sources, such as nuclear medicine.

Biomimetic construction of hierarchical MXene@PDA@CoFeOx nanohybrids towards efficient fire-safe epoxy nanocomposites with enhanced thermal conductivity and mechanical properties

Developing high-performance MXene-based polymer nanocomposites through a biomimetic method has been a research hotspot. However, it is still an intractable challenge to achieve MXene-based polymer nanocomposites with efficient fire safety, excellent thermal conductivity, and enhanced mechanical properties. Here, inspired by the adhesion of mussels, the hierarchical MXene@PDA@CoFeOx nanohybrid was fabricated by a self-assembly strategy and then employed to prepare epoxy resin (EP) nanocomposites. It has been found that MXene@PDA@CoFeOx can display excellent dispersion and interfacial compatibility in EP matrix. Thermogravimetric analysis shows that only 2.0 wt% MXene@PDA@CoFeOx results in excellent thermal stability and char yield (31.29 wt%) of EP under a nitrogen atmosphere. Combustion tests show that the 2.0 wt% MXene@PDA@CoFeOx confers efficient fire safety to EP. Remarkably, the EP-2.0%MXene@PDA@CoFeOx can obtain an attractive UL-94 rating of V0. Meanwhile, the peak heat release rate (pHRR), smoke factor (SF), and peak CO production rate (pCO) of EP-2.0%MXene@PDA@CoFeOx are dramatically decreased by 33.38%, 55.41%, and 36.84% in comparison to those of virgin EP, respectively. The efficient fire safety of EP nanocomposites is mainly attributed to the barrier effect, dilution effect, and catalytic carbonization effect of hierarchical MXene@PDA@CoFeOx. Furthermore, the MXene@PDA@CoFeOx enables EP to boast enhanced thermal conductivity (improved by 69.14%), impact strength (improved by 13.38%), and flexural strength (improved by 17.60%). This work offers a feasible biomimetic method for fabricating hierarchical MXene@PDA@CoFeOx nanohybrids and preparing efficient fire-safe EP nanocomposites with excellent thermal conductivity and mechanical performance.

Gamma ray attenuation behaviors and mechanism of boron rich slag/ epoxy resin shielding composites

Excellent thermal neutron absorption performance of boron expands the potential use of boron rich slag to prepare epoxy resin matrix nuclear shielding composites. However, shielding attenuation behaviors and mechanism of the composites against gamma rays are unclear. Based on the radiation protection theory, Phy-X/PSD, XCOM, and 60Co gamma ray source were integrated to obtain the shielding parameters of boron rich slag/epoxy resin composites at 0.015–15 MeV, which include mass attenuation coefficient (μt), linear attenuation coefficient (μ), half value thickness layer (HVL), electron density (Neff), effective atomic number (Zeff), exposure buildup factor (EBF) and exposure absorption buildup factor (EABF).μt, μ, HVL, Neff, Zeff, EBF and EABF are 0.02–7 cm2/g, 0.04–17 cm−1, 0.045–20 cm, 5–14, 3 × 1023–8 × 1023 electron/g, 0–2000, and 0–3500. Shielding performance is BS4, BS3, BS3, BS1 in descending order, but worse than ordinary concrete. μ and HVL of BS1-BS4 for 60Co gamma ray is 0.095–0.110 cm−1 and 6.3–7.2 cm. Shielding mechanism is main interactions for attenuation gamma ray by BS1-BS4 are elements with higher content or higher atomic number via Photoelectric Absorption at low energy range, and elements with higher content via Compton Scattering and Pair Production in Nuclear Field at middle and higher energy range.

Preparation and Properties of Hollow Glass Microspheres/Dicyclopentadiene Phenol Epoxy Resin Composite Materials.

With the development of the integrated circuit and chip industry, electronic products and their components are becoming increasingly miniaturized, high-frequency, and low-loss. These demand higher requirements for the dielectric properties and other aspects of epoxy resins to develop a novel epoxy resin system that meets the needs of current development. This paper employs ethyl phenylacetate cured dicyclopentadiene phenol (DCPD) epoxy resin as the matrix and incorporates KH550 coupling-agent-treated SiO2 hollow glass microspheres to produce composite materials with low dielectric, high heat resistance, and high modulus. These materials are applied as insulation films for high density interconnect (HDI) and substrate-like printed circuit board (SLP) boards. The Fourier transform infrared spectroscopy (FTIR) technique was used to characterize the reaction between the coupling agent and HGM, as well as the curing reaction between the epoxy resin and ethyl phenylacetate. The curing process of the DCPD epoxy resin system was determined using differential scanning calorimetry (DSC). The various properties of the composite material with different HGM contents were tested, and the mechanism of the impact of HGM on the properties of the composite material was discussed. The results indicate that the prepared epoxy resin composite material exhibits good comprehensive performance when the HGM content is 10 wt.%. The dielectric constant at 10 MHz is 2.39, with a dielectric loss of 0.018. The thermal conductivity is 0.1872 Wm-1 k-1, the coefficient of thermal expansion is 64.31 ppm/K, the glass transition temperature is 172 °C, and the elastic modulus is 1221.13 MPa.

Green and low-carbon upcycling of ludwigite: Prepared shields against nuclear radiation hazards and shielding mechanism

The complex composition of ludwigite makes its comprehensive usage difficult. Given the rapid development of ores in nuclear shielding materials, ludwigite was proposed to prepare epoxy resin matrix nuclear shielding composites at room temperature, which could achieve green and low-carbon upcycling. The shielding performance of neutron and gamma-ray sources was evaluated using the 241Am–Be neutron source, the Co-60 gamma-ray source and the Evaluated Nuclear Data File (ENDF). Scanning electron microscopy was used to examine the microstructures. Increasing the ludwigite weight and thickness of the shielding composite increases the shielding percentage of the prepared composites. The prepared shielding composites have macroscopic cross-sections of 0.92–1.89 cm−1, which are comparable to SWX-201, which contains 5% boron. Boron absorption and hydrogen elastic scattering are the primary shielding mechanisms for neutron attenuation in 10−11–10−6 MeV. The shielding composites’ gamma-ray shielding performance is comparable to that of water and ordinary concrete. The work is significant not only for using ludwigite but also for the shielding mechanism analysis of complex multi-element composites.

High-Strength, Degradable and Recyclable Epoxy Resin Based on Imine Bonds for Its Carbon-Fiber-Reinforced Composites

Carbon fiber (CF) is widely used in the preparation of carbon-fiber-reinforced polymer composites (CFRP) in which it is combined with epoxy resin due to its good mechanical properties. Thermosetting bisphenol A epoxy resin, as one of the most common polymer materials, is a non-renewable resource, leading to a heavy environmental burden and resource waste. To solve the above problems and achieve high mechanical and thermal properties comparable to those of bisphenol A, herein, a high-performance, degradable and recyclable bio-based epoxy resin was developed by reacting the lignin derivative vanillin with 4-amino cyclohexanol via Schiff base. This bio-based epoxy resin showed a Young's modulus of 2.68 GPa and tensile strength of 44 MPa, 36.8% and 15.8% higher than those of bisphenol A epoxy, respectively. Based on the reversible exchange reaction of the imine bond, the resin exhibited good degradation in an acidic environment and was recoverable by heat treatment. Moreover, the prepared epoxy resin could be used to prepare carbon fiber (CF)-reinforced composites. By washing off the epoxy resin, the carbon fiber could be completely recycled. The recovered carbon fiber was well preserved and could be used again for the preparation of composite materials to realize the complete recovery and utilization of carbon fiber. This study opens a way for the preparation of high-performance epoxy resin and the effective recycling of carbon fiber.

Preparation and characterization of black liquor lignin-based epoxy composite film

To fully utilize black liquor from pulping and decrease its contribution to pollution, lignin-based epoxy resin composite films were prepared from black liquor lignin. Fourier transform infrared spectroscopy indicated the successful synthesis of lignin-based phenolic amine (LPAA). Using LPAA as a curing agent, the prepared epoxy resin films (LPAAF) presented good dispersion of the inorganic chemicals of black liquor and exhibited higher tensile strength of 30 MPa and thermal stability than that using the phenolic amine as a curing agent. Therefore, LPAAF prepared from black liquor lignin presents a novel utilization of black liquor.

Plant-derived p-hydroxyphenylacrylic acid-derived epoxy resins exhibit excellent flame retardancy, hydrophobicity, degradability, and low dielectric loss after curing with bio-based fluorinated Schiff bases

Epoxy resins are designed to achieve high flame retardancy, hydrophobicity, and dielectric properties. However, the search for sustainable bio-based epoxy resin precursors that do not require additional flame retardants is still underway. Herein, we report a p-hydroxycinnamic acid-derived epoxy resin monomer (HCA-EP) obtained via a simple one-step reaction. HCA-EP can be combined with 4,4′-((2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-dial)bis(azanylylidene))bis(methanylylidene))bis(2,6-dimethoxyphenol) (SA-BTB) and cured to prepare epoxy resins(HCA-EP/SA-BTB). In comparison to HCA-EP cured with a common petroleum-based curing agent(HCA-EP/MeHHPA), such as methylhexahydrophthalic anhydride (MeHHPA), HCA-EP/SA-BTB exhibited a significantly high glass transition temperature (170 °C), excellent hydrophobic properties, and lower dielectric loss. In addition, HCA-EP/SA-BTB passed the V-0 flame rating of the UL-94 test and exhibited an ultimate oxygen index of 43.3%. Notably, it demonstrated a coke yield of 42.3% under N2 conditions, whereas that of HCA-EP/MeHHPA was 18%. Moreover, its flame-retardant index was found to be 19.8, indicating its excellent flame-retardant properties. Further, it could be degraded under acidic conditions. These findings indicate that the proposed method can be used to develop high-performance bio-based thermoset materials.

Effect of applied stress on corrosion properties of Q235 steel with multi-layer epoxy coating

Organic coating is one of the most effective, economical and universal methods for corrosion resistance of metal at a small, but the stability of the coating is highly dependent on the applied stress. In the study, a comprehensive experiment was conducted to investigate the corrosion progress of Q235 steel sheets in 3.5% NaCl solution and 10% H2SO4. The effect of applied stress on the corrosion as well as the corresponding adhesion characteristics of Q235 steel are examined and quantitatively analyzed. Results indicate that, compared with the NaCl solution, the H2SO4 solution has aggressive corrosion on the Q235 steel sheets, and the corrosion would be largely aggravated with increasing applied stress. Additionally, the decreased adhesion grade of the epoxy coating is a synergic result of the immersion time and the stress, and the continuous dissolution of the coating would lead to the aggravation of corrosion, which side-fact indicates that the prepared epoxy resin paint could show efficient anti-corrosive properties. Therefore, the stress has a direct influence on the adhesion ability of the prepared epoxy resin coating, which would decrease the anti-corrosion properties of the coating.

Facile fabrication of robust epoxy resin monolithic superhydrophobic materials with excellent mechanical-chemical stability, biocompatibility and photothermal conversion capacity

Improving the durability of superhydrophobic materials is the key factor to promote their practical application. Here, a facile one-pot synthesis procedure is used to prepare epoxy resin monolithic superhydrophobic materials (ER-MSM) with excellent mechanical strength, chemical stability, oil-water separation, stain liquids repellency, biocompatibility and excellent photothermal conversion capacity. The mechanical strength and hydrophobic durability of ER-MSM are improved by synchronously processes of bubbles impact, high temperature curing and chemical bonding of epoxy resin to form micropores. The prepared monolithic material can maintain water repellency even after sandpaper abrasion, ultrasonication, multiple knife scratch, finger wiping, and exposure to UV irradiation and high-temperature calcination. The biocompatibility of ER-MSM was further proved by the 95 % cell viability of the PC12 cells after contacting with ER-MSM for 70 min. ER-MSM has excellent photothermal conversion ability by dopamine coreaction in the one-pot synthesis procedure (named as PER-MSM). The photothermal conversion capacity of PER-MSM can be regulated by adjusting the concentration of dopamine. The surface temperature easily exceeds 70 °C after 808 nm laser irradiating for 200 s under power density of 1 W/cm2 and dopamine concentration larger than 10 mg/mL or under power density of 2 W/cm2 and dopamine concentration larger than 2 mg/mL. The alcohol-based reaction system without complex fabrication steps, expensive, or toxic fluoride, satisfies the environment-friendly requirements. Therefore, the prepared mechanochemically stable and photothermal superhydrophobic materials have great potential applications in oil-water separation, self-cleaning and other industrial fields.

Effect of heating rate and feedstock nature on electrical conductivity of biochar and biochar-based composites

Cost-effective strategies for integrating bio-oil production with biochar utilization in new sustainable platforms are needed to improve the economic viability of pyrolysis for energy applications. Recently, the use of biochar as filler in the preparation of polymer based composites received a great attention due to its ability to improve polymers mechanical, electrical and thermal properties.This work aims to expand knowledge on the effect of the heating rate and feedstock chemical composition on the on the biochar structural and chemical characteristics affecting electrical properties of the biochar at different pyrolysis temperatures. Biochars were produced from three feedstocks, namely walnut shells (WS), the lignin rich residue from bio-ethanol production (LRR) and sewage sludge (SS), under slow and fast heating rate at 500, 600 and 700°C. The three feedstock differ for both the organic components (i.e. high lignin content in WS and LRR and presence of proteins in SS) and ash content which is highest in SS.The produced biochars were characterized and the observed differences in their chemical and structural properties were discussed in relation to their effect on the measured electrical conductivity.The severity of the pyrolysis treatment improved biochars electrical conductivity. Heating rate and feedstock type affected the electrical conductivity only marginally at 500 and 600°C, whereas at 700°C any relevant effect was observed. WS biochars produced at 500 and 600°C exhibited the lowest electrical conductivity regardless of the heating rate of the production process.The biochars produced at 700°C were used to prepare epoxy resins composites. Despite their comparable conductive performance, the biochars lent different electrical conductivity to the composites depending on the biomass type and the heating rate experienced by the biomass samples during the pyrolytic treatment. The composite prepared with WS biochar produced under fast heating rate exhibited the highest electrical conductivity.

Performance and interaction mechanism of a new highly efficient benzimidazole-based epoxy resin for corrosion inhibition of carbon steel in HCl: A study based on experimental and first-principles DFTB simulations

Thanks to their excellent properties, epoxy resins are the first choice for many engineering applications. In this regard, herein, a new epoxy resin, namely 1-(oxiran-2-ylmethyl-1H-benzo[d]imidazole (BIZ epoxy), was synthesized and characterized by nuclear magnetic resonance (1H, 13C NMR) and Fourier transform infrared-attenuated total reflection (FTIR-ATR)) techniques. The corrosion inhibition properties of prepared epoxy resin for carbon steel (CS) in 1.0 mol/L HCl were evaluated using electrochemical and scanning electron microscope (SEM) techniques. Furthermore, reactivity and interaction mechanisms between epoxy resin molecule and the iron surface were investigated using quantum chemical parameters (QCPs) and Density-Functional Tight-Binding (DFTB). Electrochemical studies by potentiodynamic polarization curves (PPC) and electrochemical impedance spectroscopy (EIS) showed that the BIZ epoxy acted as a barrier against the acid corrosion of CS with an inhibition efficiency of 93 % at 1 mmol/L. The adsorption of BIZ epoxy followed the Langmuir adsorption isotherm and was found to be a physicochemical process. The SEM analysis showed a significant difference in surface morphology of CS after inhibition due to the formation of a protective barrier. DFTB simulation of BIZ epoxy – Fe(110) surface revealed the formation of a chemical bond and several long-range van der Waals interactions. The projected density of states (PDOS) of isolated and adsorbed systems confirmed the physicochemical nature of interactions between inhibitor molecule and Fe(110) surface.

Anticorrosive epoxy coatings from direct epoxidation of bioethanol fractionated lignin

The development of lignin-based anticorrosive epoxy coatings for steel protection is beneficial for both alleviating the fossil resource depletion and value-added utilization of lignin but remains a challenge due to the inherent heterogeneous structure of lignin. Here, we selectively extract the low molecular weight (MW) fraction of a crop residue-derived enzymatic hydrolysis lignin (EHL) through a bioethanol fractionation process and prepare epoxy resin by direct epoxidation of the bioethanol fractionated lignin (BFL). The coatings are then fabricated using 20–100 wt% of BFL-based epoxy resin (LEp) as the commercial epoxy resin substitute. The low MW and high p-hydroxyphenyl content of the BFL offer high solubility and good workability for BFL and LEp during epoxidation and coating production, respectively. Lignin-based coatings with 20–40 wt% LEp exhibit good adhesion property (5B) and superior corrosion resistance, compared to the commercial epoxy coating. Although coating with high LEp concentrations (i.e., 60–100 wt%) resulted in decreased adhesion strength, the coating with 100 wt% LEp still displayed corrosion protection performance comparable to that of the commercial epoxy coating. Overall, this study provides a simple and effective approach to converting lignin to epoxy resins for a wide variety of surface coating applications.

Synthesis of a highly efficient flame retardant containing triazine and pentaerythritol phosphate groups and its intumescent flame retardancy on epoxy resin

A novel phosphorus-nitrogen-containing flame retardant (DOPT) has been successfully synthesized via the substitution reaction of cyanuric chloride, pentaerythritol phosphate and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The chemical structure of DOPT was confirmed by 1H, 31P and 13C nuclear magnetic resonance, Fourier transform infrared spectroscopy and elemental analysis. Then, flame retardants were added to epoxy resin to prepare epoxy resin composites by pouring method. Thermal properties, flame retardancy, and combustion behavior of epoxy resin composites were evaluated by thermogravimetric analysis, vertical burning, limiting oxygen index and cone calorimeter test. Thermogravimetric analysis test showed that the carbon residue rate of DOPT at 800°C reached 52.53%, which indicated that the introduction of high-efficiency char-forming agent triazine and pentaerythritol phosphate groups could significantly improve its char-forming performance and thermal stability. The epoxy resin composite achieved vertical burning V-0 grade and the limiting oxygen index value reached 35.5% when 7 wt% DOPT was incorporated. Furthermore, the cone calorimeter test results manifested that the addition of DOPT stimulated degradation of the epoxy resin matrix during the combustion process and accelerated the formation of an expanded and dense carbon layer. Additionally, the incombustible gas produced during the decomposition of DOPT had played a flame-retardant effect in the gas phase. Hence, compared with neat epoxy resin, the total heat release and total smoke production of the EP-7 wt% DOPT composite decreased by 14.0% and 25.3%, respectively. Moreover, owing to the excellent compatibility and the strong interface effect between DOPT and epoxy resin, the addition of DOPT also enhanced the mechanical and fire resistance properties of the epoxy resin composite. Therefore, it is proposed that DOPT could be exploited as an economical and high-efficiency flame retardant, and it has considerable prospects in flame retardant epoxy resin composites.

Study on Surface Discharge Characteristics of GO-Doped Epoxy Resin-LN2 Composite Insulation.

Superconducting power lead equipment for epoxy insulation, such as high-temperature superconducting DC power or liquefied natural gas energy pipelines, as well as high-temperature superconducting cables, has long been used in extreme environments, from liquid nitrogen temperatures to normal temperatures. It is easy to induce surface discharge and flashover under the action of strong electric field, which accelerates the insulation failure of current leads. In this paper, two-dimensional nano-material GO was used to control the electrical properties of epoxy resins. The DC surface discharge and flashover characteristics of the prepared epoxy resin–GO composite insulation materials were tested at room temperature with liquid nitrogen. The surface discharge mechanism of the epoxy resin–GO composite insulation materials was analyzed. The experimental results show that the insulation properties of epoxy composites doped with GO changed. Among them, the surface flashover voltage of 0.05 wt% material is the best, which can inhibit the discharge phenomenon and improve its insulation properties in extreme environments, from room temperature to liquid nitrogen temperature. It is found that the development process of surface discharge of composite insulating materials under liquid nitrogen is quite different from that under room temperature. Before critical flashover, the repetition rate and amplitude of surface discharge remain at a low level until critical flashover. Furthermore, the voltage of the first flashover is significantly higher than that of the subsequent flashover under the action of the desorption gas on the surface of the composite insulating material and the gasification layer produced by the discharge. Given that the surface flashover voltage of 0.05 wt% epoxy composite is the best, the research and analysis of 0.05 wt% composite is emphasized. In the future design of superconducting power lead insulation, the modification method of adding GO to epoxy resin can be considered in order to improve its insulation performance.

A bio-based epoxy resin derived from p-hydroxycinnamic acid with high mechanical properties and flame retardancy

Recent advances in epoxy resins have been forward to achieving high mechanical performance, thermal stability, and flame retardancy. However, seeking sustainable bio-based epoxy precursors and avoiding introduction of additional flame-retardant agents are still of increasing demand. Here we report the synthesis of p-hydroxycinnamic acid-derived epoxy monomer (HCA-EP) via a simple one-step reaction, and the HCA-EP can be cured with 4,4′-diaminodiphenylmethane (DDM) to prepare epoxy resins. Compared with the typical petroleum-based epoxy resin, bisphenol A epoxy resin, the HCA-EP-DDM shows a relatively high glass transition temperature (192.9 °C) and impressive mechanical properties (tensile strength of 98.3 MPa and flexural strength of 158.9 MPa). Furthermore, the HCA-EP-DDM passes the V-1 flammability rating in UL-94 test and presents the limiting oxygen index of 32.6%. Notably, its char yield is as high as 31.6% under N2, and the peak heat rate release is 60% lower than that of bisphenol A epoxy resin. Such findings provide a simple way of using p-hydroxycinnamic acid instead of bisphenol A to construct high-performance bio-based thermosets.