Dielectric Properties Of Epoxy Resin Research Articles

Enhancing flame retardancy and dielectric performance of epoxy resins through benzoxazine-phosphorus modification

A P/N-containing flame retardant, DOPOBH, was synthesized with salicylaldehyde, p-aminophenol, 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) and formaldehyde. The performance of DOPOBH in flame retardant modification of 4,4′-diaminodiphenyl sulfone(DDS)/diglycidyl ether of bisphenol A (DGEBA, E−44) system was studied in terms of limiting oxygen index (LOI), vertical burning testing (UL-94) and cone calorimeter test (CCT). When the phosphorus content was 1.5 wt% of the whole system, DOPOBH modified epoxy resin (EP/P1.5) exhibited excellent flame retardancy (achieving a UL-94 V-0 rating and the LOI value of 35.2 %). Compared with pure EP, a 54.3 % decrease of peak heat release rate (PHRR) and ca. 5 times of residue (with an intumescent structure) was obtained with EP/P1.5 in CCT. Based on the results of CCT, scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and thermogravimetry-infrared spectroscopy (TG-IR), DOPOBH was verified to play important roles in both gas phase and solid phase. In addition, the addition of DOPOBH could improve the dielectric properties of epoxy resin and provide new strategies for high-performance applications in electronic packaging.

XGBoost Regression Analysis of Dielectric Properties of Epoxy Resin with Inorganic Hybrid Nanofillers

Our research described in this paper investigated the influence of varying weight percentages of a hybrid nano filler composed of titanium dioxide (TiO2) and silicon dioxide (SiO2) in an epoxy polymer composite. The dielectric properties were analyzed across a broadband frequency range. Additionally, X-ray diffraction (XRD) was employed to examine the structural changes and crystalline phases within the composite materials. The Influence of hybrid inorganic nano-fillers in the epoxy composite on the dielectric properties are discussed thoroughly in this report. To improve material design and prediction modeling, our research utilized machine learning algorithms, such as the XGBoost regressor. The aim was to assess the effectiveness of regression techniques in evaluating the material properties. By employing performance metrics, like R2 score and RMSE, the tests could achieve accuracies ranging from 30% to 60%. Simulation results demonstrated that machine learning-based methods can significantly expedite the forecasting of the dielectric properties, i.e. dielectric constant and dielectric loss at intermediate frequencies, thereby saving both time and energy.

Enhanced dielectric properties of titanium Dioxide/Epoxy nanocomposites with different filler crystal form

In this work, two different types of titanium dioxide, anatase and rutile, were blended into a bisphenol-A epoxy resin. The dielectric properties of epoxy nanocomposites were measured to investigate whether the filler crystal form affects the behaviors of epoxy resin. All nanoparticles have a same size of ∼ 60 nm and the content of the nanocomposites is from 1 to 4 wt%. The dielectric properties of epoxy nanocomposites, including complex permittivity dependence on frequencies, volume resistivity, and breakdown strength were measured. Although the band gap of anatase-type titanium dioxide is smaller than that of rutile-type titanium dioxide, its epoxy nanocomposite has a higher volume resistivity and a higher breakdown strength at each filler content. The anatase-type titanium dioxide is more favorable than rutile-type titanium dioxide to improve the dielectric properties of epoxy resin.

Effects of cross‐linked networks on dielectric properties of epoxy resins based on molecular dynamics

AbstractIn this paper, three epoxy resin systems commonly used in power equipment are prepared to obtain cross‐linked networks with structural differences. The relationship between microscopic structures and dielectric properties of epoxy resins is investigated and discussed. Experimental results show that the polarization and conductance losses are inhibited in the anhydride‐cured systems with methyl groups. The molecular dynamics (MD) simulation shows that rigid anhydride structures (such as methyl groups) play a major role in reducing the local segment mobility and increasing the free volume at cross‐linking points. The decrease in local segment mobility has been confirmed by the decrease of mean square displacement (MSD) at the cross‐linking points, which is consistent with the change of measured polarization and conductance loss. In the glassy state, the dielectric properties of different anhydride‐cured systems can be reflected by local MSD at the cross‐linking points. At high temperatures near the glass transition temperature, both the free volume and network mobility increase significantly, which reflects the increased dielectric relaxation strength and conductance loss. The understanding of the structure–property relationships could provide a theoretical foundation for epoxy modification in a controlled manner for power equipment applications.

Effects of Graphene Oxide Dimension on the Mechanical and Dielectric Properties of Epoxy Resin

Effects of Graphene Oxide Dimension on the Mechanical and Dielectric Properties of Epoxy Resin

Effect of the Structure of Epoxy Monomers and Curing Agents: Toward Making Intrinsically Highly Thermally Conductive and Low-Dielectric Epoxy Resins.

The low intrinsic thermal conduction and high dielectric properties of epoxy resins have significantly limited their applications in electrical and electronic devices with high integration, high frequency, high power, and miniaturization. Herein, a liquid crystalline epoxy (LCE) monomer with a biphenyl mesogenic unit was first synthesized through an efficient one-step reaction. Subsequently, bisphenol AF (BPAF) containing low-polarizable -CF3 groups and 4,4'-diaminodiphenylmethane (DDM) were applied to cure the LCE and commercial diglycidyl ether of bisphenol A-type epoxy (E-51), respectively, to afford four kinds of epoxy resins with various intrinsic thermal conductivity and dielectricity values. Owing to the dual effect of microscopically stacking of mesogens and the contribution of fluorine to the formation of liquid crystallinity, ordered microstructures of the nematic liquid crystal phase were formed within the cross-linking network of LCE as confirmed by polarized optical microscopy and X-ray diffraction. Consequently, phonon scattering was suppressed, and the intrinsic thermal conductivity was improved considerably to 0.38 W/(m·K), nearly twice as high as that of E-51 cured with DDM (0.20 W/(m·K)). Additionally, the ordered microstructure and ultralow polar -CF3 groups within LCE cured with BPAF enabled the epoxy resin to exhibit a remarkably lower and stable dielectric constant (ε) and dielectric loss tangent (tan δ) over both low and high frequencies compared to E-51 cured with DDM. The ε decreased from 3.40 to 2.72 while the tan δ decreased from 0.044 to 0.038 at 10 GHz. This work presents a scalable and facile strategy for breaking the bottleneck of making epoxy resins simultaneously with high inherent thermal conduction and low dielectric performance.

Multifunctional phosphorus-containing porphyrin dye for efficiently improving the thermal, toughness, flame retardant and dielectric properties of epoxy resins

To promote the application potential of epoxy resins (EPs) in electronic packaging, a novel phosphorus-containing porphyrin (PPR) dye was designed and synthesized to enhance the thermal, mechanical, flame retardant and dielectric properties of EPs. Incorporating PPR can efficiently improve the glass transition temperature (Tg) and thermodynamic properties of bisphenol-A EP. Meanwhile, PPR exhibited a significant toughening effect for EP with an enhancement of 59.5 % of elongation at the break without any stress sacrifice. Moreover, the loading of only 5 wt% PPR led to the UL-94 V-0 rating for EP. When 7 wt% PPR was added into EP, the peak heat release rate (PHRR) and total smoke production (TSP) were reduced by 44.3 % and 14.6 %, respectively, indicating the distinguished flame retardant properties. More importantly, the dielectric constant of EP composites gradually decreased with the increasing loading of PPR. This work provides a feasible approach to create EP composites via incorporating P-based porphyrin which are promisingly utilized as electronic packaging materials in integrated circuits field.

Novel Bio-Based Materials: From Castor Oil to Epoxy Resins for Engineering Applications.

The paper presents the synthesis and thermal behavior of novel epoxy resins prepared from epoxidized castor oil in the presence of or without trimethylolpropane triglycidyl ether (TMP) crosslinked with 3-hexahydro-4-methylphtalic anhydride (MHHPA) and their comparison with a petroleum-based epoxy resin (MHHPA and TMP). Epoxidized castor oil (ECO) was obtained via in situ epoxidation of castor oil with peroxyacetic acid. The chemical structures of castor oil (CO), ECO, and epoxy matrix were confirmed using FT-IR and 1H-NMR spectroscopy. The morphological and thermal behavior of the resulting products have been investigated. Compared to petroleum-based resins, castor oil-based ones have a lower Tg. Anyway, the introduction of TMP increases the Tg of the resins containing ECO. The morphological behavior is not significantly influenced by using ECO or by adding TMP in the synthesis of resins. The dielectric properties of epoxy resins have been analyzed as a function of frequency (1 kHz-1 MHz) and temperature (-50 to 200 °C). The water absorption test showed that as Tg increased, the percent mass of water ingress decreased.

Anomalous Residual Stress Behavior and Corresponding Dielectric Properties of Epoxy Resin Induced by Physical Aging

In this paper, we report an anomalous behavior of residual stress in epoxy resin insulation, which decreased with elevated cooling rate from an initial temperature below the glass transition temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ). It was found that an increased cooling rate from 9 K/h to 120 K/h led to a decreased residual stress by 37%. Further results of dielectric relaxation and volumetric strain suggest the physical aging as the origin of this anomalous residual stress behavior, which resulted in enhanced chain relaxation on the micro level and volumetric shrinkage on the macro level. It is suggested that the larger residual stress is caused by both greater interaction between chains and larger volumetric shrinkage in the specimens with lower cooling rate. In addition, shortened cooling time also induced insufficient chain curling and thus increased free volume, which can be further supported by enhanced charge mobility and lowered DC breakdown strength. A 13% decrease in breakdown strength and a 38% increase in the charge mobility were found provided the cooling rate enhanced from 9 K/h to 120 K/h. This work proposed a new comprehending into the residual stress from curing cooling process and corresponding dielectric properties of epoxy resin insulation.

Preparation of Hydrophobic Low-k Epoxy Resins with High Adhesion Using a Benzocyclobutene-Rosin Modifier

With the development of high-frequency communication, the miniaturization of integrated circuits (ICs) has led to interconnected signal delays and losses. The dielectric properties of epoxy resins are no longer satisfactory, because of the presence of polar groups. Herein, a benzocyclobutene-rosin modifier was designed and synthesized to reduce the dielectric constant of epoxy resins. The recross-linking network of benzocyclobutene inhibits the polarizability of the polar groups, and rosin skeletons increase the free volume of epoxy resins. Consequently, the dielectric constant of epoxy resins decreased from 3.12 to 2.72 and their water absorption decreased from 1.06% to 0.861%. The dielectric constant and water absorption are lower than those of most commercial dielectric materials. Additionally, the adhesion of epoxy resins was improved, which broke the contradiction between the dielectric properties and the adhesion of traditional epoxy resins. The modified epoxy resin was finally applied to printed circuit boards. At 15 GHz, its signal loss was 28.8 dB, which was lower than that of a commercial epoxy resin (FR-4), demonstrating that the modified epoxy resin can better meet the miniaturization needs of ICs.

Enhancing toughness, flame retardant, hydrophobic and dielectric properties of epoxy resin by incorporating multifunctional additive containing phosphorus/silicon

Developing epoxy resins with superior toughness, flame retardant and hydrophobic as well as dielectric properties remains a huge challenge. Herein, an epoxy additive (ETP) was prepared by grafting phosphorus-containing molecules into the skeleton of silicone resin through silicon hydrogen addition reaction. Through such a design, the obtained ETP imparted Bisphenol A epoxy resin (DGEBA) with excellent flexibility, fire safety, hydrophobicity and dielectrical property. When only 6 wt% of ETP was introduced into the DGEBA system, the resulting product (ETP-6) passed the V-0 level in the UL-94 test with a high limiting oxygen index of 29.8 %, which could be ascribed to the presence of phosphorus and silicon element. Meanwhile, compared with neat DGEBA, the peak heat releases and smoke emissions of ETP-6 were reduced by 32.7 % and 37.8 % during the combustion. Additionally, ETP also imparted the cured product with excellent hydrophobic and dielectric properties, as well as superior toughness (114.5 % increase in impact strength) due to its “rigid and flexible” silicone skeleton and good dispersion. This work opens up a new strategy for developing high-performance and multifunctional epoxy resin additives with potential versatile applications.

Curing Degree Dependence of Dielectric Properties of Bisphenol-A-Based Epoxy Resin Cured With Methyl Hexahydrophthalic Anhydride

The dielectric properties of epoxy resin mainly depend on its microstructures, especially the curing degree. In this article, the reaction process of diglycidyl ether of bisphenol A (DGEBA)/methyl hexahydrophthalic anhydride (MHHPA) system is studied by differential scanning calorimetry, and samples with different curing degrees are prepared by regulating the curing temperature and time. The evolution of microstructure during epoxy resin crosslinking is simulated by molecular dynamics simulation. It is found that the effect of the curing degree on dielectric properties can be attributed to the distribution of polar groups and the mobility of chain segments, while the contribution of free volume is insignificant. With the increase of the curing degree, the epoxy group at the chain end is transformed into an ester group with weaker polarity, as well as the epoxy molecular segments are combined more closely and the mobility of molecules decreases, resulting in an improvement in the dielectric properties of the epoxy resin.

Influence of neutron irradiation on the mechanical and dielectric properties of epoxy/ titanium oxide nanocomposite

The exposure of polymeric insulation in nuclear power plants necessitates the study of the effect of neutron irradiation on the mechanical and dielectric properties of neat and nano-filled polymeric-based insulation materials. The exposure of the materials to ionizing radiation can influence their dielectric and insulating properties. This work presents the influence of neutron irradiation on the dielectric behavior of neat and nanoparticle-filled Epoxy-TiO2 nanocomposite. The prepared neat and nanocomposite samples were exposed to neutron radiation in the Nigeria Research Reactor I (NIRR-I). The mechanical and dielectric analyses of the samples were performed before and after irradiation. The presence of 2 wt% TiO2 nanoparticles in the epoxy matrix resulted in optimum mechanical and dielectric behavior. While the presence of the nanoparticles seems to have a significant influence on the reduction of the mechanical degradation of the composite (39.96%–12.11% after exposure to 4.5 kGy), it does not have much influence on the reduction of the dielectric loss of the composite. The variation of temperature of the sample revealed that the 2 wt% nanoparticles filled polymer displayed higher relaxation activated energy. The research suggests that the filling of the epoxy polymer with 2 wt% TiO2 nanoparticles can modify the mechanical and dielectric relaxation behavior of the polymer composites. This could enhance the resistance of the composite material to the effect of radiation-induced degradation in the polymeric insulation.

Effect of Temperature on the Charge Transport Behavior of Epoxy/Nano-SiO2/Micro-BN Composite.

Thermally conductive epoxy resin composites are widely used as electrical equipment insulation and package materials to enhance heat dissipation. It is important to explore the dielectric properties of the composites at high temperatures for the safe operation of the equipment. This paper investigated the charge transport behavior of an epoxy/nano−SiO2/micro−BN composite at varied temperatures by combined analysis of the TSDC (thermally stimulated current), conduction current, complex permittivity and space charge distribution between 40 and 200 °C. The results show that ionic space charge accumulation was significantly suppressed in the composite at high temperatures. The conduction current increased gradually with temperature and manifested a remarkable shift from electron charge transport to ion charge transport near the glass transition temperature (Tg). The real and imaginary permittivity showed an enormous increase above Tg for both the epoxy resin and the composite. The conduction current and permittivity of the composite were remarkably reduced in comparison to the epoxy resin. Therefore, the ionic process dominated the high temperature dielectric properties of the epoxy resin and the composite. The nano–micro fillers in the composite can significantly inhibit ion transport and accumulation, which can significantly enhance the dielectric properties of epoxy resin. Thus, the nano–micro composite has a strong potential application as a package material and insulation material for electronic devices and electrical equipment operated at high temperatures.

Double organic groups‐containing polyhedral oligomeric silsesquioxane filled epoxy with enhanced fire safety

AbstractTo simultaneously improve the flame retardancy, smoke suppression, mechanical properties, and dielectric properties of epoxy resin (EP), a series of polyhedral oligomeric silsesquioxane containing vinyl and epoxy groups (EV‐POSSs) was designed and successfully synthesized. The results of Fourier transform infrared (FT‐IR), Nuclear Magnetic Resonance (NMR) and mass spectra indicated that the EV‐POSSs possessed two main cage structures, T10 and T12. The epoxy groups attaching to POSS connected the polymer main chains, forming higher crosslinking‐density networks. The self‐polymerization of vinyl groups under high temperatures improved the mechanical property and the quality of char residues. Based on our study, the introduction of EV‐POSSs can enhance the flame retardancy, smoke suppression, mechanical and dielectric properties. Compared with pure EP, the dielectric constant of EP containing 2 wt% EV‐POSS dropped from 3.9 to 3.6 at 106 Hz. In addition, with the 10 wt% EV‐POSSs, the peak of heat release rate and total smoke production also reduced by 50.7% and 36.7%, respectively. Most notably, the maximum smoke density declined by 44.8% due to the EV‐POSSs simultaneously containing epoxy and vinyl groups show comprehensive enhancement and occupy spacious applications.

A nitrogen heterocyclic/phosphaphenanthrene derivative as a reactive additive for simultaneous improvement of flame retardancy, mechanical and dielectric properties of epoxy resins

Various approaches have been successfully applied to solve the flammability of epoxy resin (EP) materials, but enhanced flame retardance of EP is often along with deteriorated glass transition temperature (Tg) and mechanical property. In order to prepare EP composites with good comprehensive performance, we synthesized a phosphorus-containing triazole derivative named TBO from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3,5-diamino-triazolz and salicylaldehyde, and attached it into epoxy framework. With 0.75 wt% phosphorus loading, the 0.75-TBO/EP composite had a V-0 rating and a limiting oxygen index of 33%. 1.0-TBO/EP composite also had a V-0 rating and acquired a decrease of 37.6% in peak heat release rate. In addition, the tensile strength and flexural strength of 0.75-TBO/EP increased to 63.9 MPa and 146 MPa from 59 MPa and 134 MPa of EP respectively. Meanwhile, the Tg values of TBO/EP elevated to some certain compared to EP. In a word, EP modified with TBO composites owned strong mechanical property, higher Tg and excellent flame retardance, indicating great potential for application.

Fabrication of melamine trimetaphosphate 2D supermolecule and its superior performance on flame retardancy, mechanical and dielectric properties of epoxy resin

To improve the flame retardancy, mechanical and dielectric properties of epoxy resin (EP), a novel two-dimensional (2D) supermolecule, melamine trimetaphosphate (MAP), is successfully synthesized using melamine (MA) and sodium trimetaphosphate (STMP) in aqueous solution. Its chemical, crystalline structure and thermal stability are thoroughly characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), atom force microscope (AFM) and thermo-gravimetric analysis (TGA) techniques. Then EP-MAP composites are prepared, and their morphologies are assessed by SEM, thermal stability by TGA, fire retardancy by limiting oxygen index test (LOI), vertical burning standard test (UL-94), and cone calorimeter tests, mechanical properties by stress strain tests, and dielectric properties by impedance analyzer. The results show that the MAP layers are formed by a 3:1 combination of MA and STMP rings via intermolecular hydrogen bonding. The MAP sheets with a thickness of around 2 nm show high thermal stability. Compared to pure EP, the thermal stability of EP-MAP is improved, and EP-MAP composite can achieve 30.0% of LOI value and UL-94 V-0 rating with only 4% MAP. Meanwhile its peak of heat release rate is reduced by 65.6% and the smoke release is highly suppressed in the cone calorimeter test. The typical intumescent flame retardancy effect and phosphorus-nitrogen ( P –N) effect during the combustion of EP-MAP are demonstrated by X-ray photoelectron spectroscopy (XPS) and thermogravimetric analyzer coupled with Fourier transform infrared analysis of evolving products (TGA-FTIR). Due to the uniform dispersion of MAP in EP matrix, the mechanical and dielectric properties of EP-MAP are also significantly enhanced.

Effects of Gradient Magnetic Field on Charge Behavior and Electrical Tree Growth in Epoxy Resin

In this paper, a high-field magnet experimental system is setup to investigate the dielectric properties of epoxy resin in the presence of high magnetic field. An asymmetric ferromagnetic electrode system is used to build gradient magnetic field and investigate its effect on tree characteristics of epoxy resin. Influence mechanisms of gradient magnetic field on dielectric properties and tree characteristics of epoxy resin are discussed through combining experimental results and simulation calculation. Experimental results show that electrical trees are more easily to be initiated and spread more rapidly in gradient magnetic field. The conductivity of the epoxy resin increases with the increase of magnetic field strength due to energy level splitting, which is analyzed through electrodynamics calculation. The relative permittivity decreases, and the dielectric loss tangents increase when high magnetic field is applied. Changes of conductivity and relative permittivity affect the charge behavior and electric field distribution in epoxy resin, resulting in the particular electrical tree.

Thermal and dielectric properties of epoxy resin filled with double-layer surface-modified boron nitride nanosheets

Owing to the rapid development of advanced power system and modern micro-electronic devices, exploiting composites with excellent thermal conductivity and dielectric properties has become increasingly important. In this work, a double-layer surface modification method of grafting dopamine (DA) at the end of 3-glycidoxypropyl-trimethoxysilane (KH560) is firstly proposed to modify the surface of boron nitride nanosheet (BNNS), for improving the thermal conductivity and dielectric properties of epoxy resin (EP). Besides, the thermal conductivity of EP composites with double-layer surface-modified BNNSs and its improvement mechanism is explored with molecular dynamics (MD) simulation from micro level. The results illustrate that thermal conductivity of EP composites doped with double-layer modified BNNSs by grafting DA at the end of KH560 (DKBP) is 0.252 W/(m·K), 129% higher than EP. Moreover, this double-layer surface modification method of DKBP is beneficial to enhance the heat transfer effect and reduce scattering effect at the interface, which is the essential reasons for improving thermal conductivity of composites. Meanwhile, DKBP composite also presents superior dielectric properties. This work provides a promising idea to develop new insulating materials with high thermal conductivity.

Magnetic and Dielectric Properties of Epoxy Composites Reinforced with Hybrid Nanoparticle iron oxide (Fe3O4) and nickel (Ni)

In this research, the effects of hybrid nanoparticles Fe3O4+Ni on the magnetic and dielectric properties of epoxy resin are investigated. Microstructural characterization was performed by Field Emission scanning electron microscopy FESEM, X-ray diffraction spectra XRD, and Fourier-transform infrared spectroscopy (FTIR). The magnetic properties were investigated by vibrating sample magnetometer (VSM) and the dielectric response was investigated by a precision impedance analyzer (Agilent 4294A) LCR meter at room temperature with different frequencies. The study dealing with hybrid nanocomposite (epoxy/Fe3O4+Ni) consisting of epoxy resin as the matrix material reinforcing by magnetite nanoparticles (Fe3O4) with different weight percentages (3wt.%, 6wt.%, 9wt.%, 12wt.%, 15wt. %) and constant weight percentage 2wt% of nickel (Ni) nanoparticles. The samples were prepared using the casting method. The epoxy with the hardener is weighted and mixing in a 2:1 ratio and then add reinforcement materials Fe3O4+Ni into the epoxy. Microstructural analysis showed that a uniform distribution and homogeneously dispersed in the epoxy matrix. The results of this work exhibit that the Increasing additive weight percentages of Fe3O4 nanoparticles with a constant weight of Ni nanoparticles into epoxy resin led to improvement in the magnetic and electric properties of hybrid nanocomposites compared with pure epoxy.