Effect of backbone moiety in epoxies on thermal conductivity of epoxy/alumina composite

We chose two commercial epoxies, bisphenol A diglycidyl ether (DGEBA) and 3,3′,5,5′‐tetramethyl‐4,4′‐biphenol diglycidyl ether (TMBP), and synthesized one liquid crystalline epoxy (LCE), 4′4′‐bis(4‐hydroxybenzylidene)‐diaminophenylene diglycidyl ether (LCE‐DP) to investigate the effect of backbone moiety in epoxies on the thermal conductivity of epoxy/alumina composite. The DGEBA structure shows an amorphous state and the TMBP structure displays a crystal phase, whereas the LCE‐DP structure exhibits a liquid crystalline phase. The curing behaviors of them were examined employing 4,4′‐diaminodiphenylsulfone (DDS) as a curing agent. The heat of curing of epoxy resin was measured with dynamic differential scanning calorimetry (DSC). Alumina (Al₂O₃) of commercial source was applied as an inorganic filler. Thermal conductivity was measured by laser flash method and compared with value predicted by two theoretical models, Lewis‐Nielsen and Agari‐Uno. The results indicated that the thermal conductivity of the LCE‐DP structure was larger than that of the commercial epoxy resins such as TMBP and DGEBA and the experimental data fitted quite well in the values estimated by Agari‐Uno model. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Synthesis of a novel biphenyl epoxy resin and its hybrid composite with high thermal conductivity

A novel biphenyl epoxy monomer of p-methyl phenylhydroquinone epoxy resin (p-MEP) was synthesized and characterized. We researched its potential in the area of thermal conduction application and prepared a series of hybrid composites based on it with different mass ratios of sphere Al₂O₃ filler. From the good mobility and low viscosity of p-MEP, it allowed mixing with more Al₂O₃ fillers. The hybrid epoxy resins owned the advantages of traditional epoxy resins as well as quite considerable thermal conductivity. Therefore, the hybrid composite at the maximum mass fraction of 70% possess the highest thermal conductivity of 5.6 W mK⁻¹, which is 5.6 times higher than that of pristine p-MEP (0.1 W mK⁻¹). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47078.     

Curing behavior and thermal and mechanical properties enhancement of tetraglycidyl‐4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone using a liquid crystalline epoxy

A thermosetting resin system, based on tetraglycidyl‐4,4′‐diaminodiphenylmethane, has been developed via copolymerization with 4,4′‐diaminodiphenylsulfone in the presence of a newly synthesized liquid crystalline epoxy (LCE). The curing behavior of LCE‐containing resin system was evaluated using curing kinetics method and Fourier transform infrared spectroscopy. The effect of LCE on the thermal and mechanical properties of modified epoxy systems was studied. Thermogravimetric analysis indicated that the modified resin systems displayed a high T_0.05 and char yield at lower concentrations of LCE (≤5 wt%), suggesting an improved thermal stability. As determined using dynamic mechanical analysis and differential scanning calorimetry, the glass transition value increased by 9.7% compared to that of the neat resin when the LCE content was 5 wt%. Meanwhile, the addition of 5 wt% of LCE maximized the toughness with a 175% increase in impact strength. The analysis of fracture surfaces revealed a possible effect of LCE as a toughener and showed no phase separation in the modified resin system, which was also confirmed by dynamic mechanical analysis. © 2016 Society of Chemical Industry     

Curing and Morphology of BPA Epoxy Resin/LC Epoxy Resin PEPEB Composites

Liquid crystalline epoxy resin (LC epoxy resin) – p-phenylene di{4-[2-(2,3-epoxypropyl)ethoxy]benzoate} (PEPEB) was synthesized. The mixture of PEPEB with bisphenol-A epoxy resin (BPAER) was cured with a curing agent 4,4-diamino-diphenylmethane (DDM). The curing process and thermal behavior of this system were investigated by differential scanning calorimeter (DSC) and torsional braid analysis (TBA). The morphological structure was measured by polarizing optical microscope (POM) and scanning electron microscope (SEM). The results show that the initial curing temperature Ticu (gel point) of this system is 68.1°C, curing peak temperature T _pcu is 102.5°C, and the disposal temperature T _fcu is 177.6°C. LC structure was fixed in the cured epoxy resin system. The curing kinetics was investigated by dynamic DSC. Results showed that the curing reaction activation energy of BEPEB/BPAER/DDM system is 22.413 kJ/mol. The impact strength is increased 2.3 times, and temperature of mechanical loss peak is increased to 23°C than the common bisphenol-A epoxy resin, when the weight ratio of BEPEB with BPAER is 6 100.     

Liquid crystalline epoxy resin modified cyanate ester/epoxy resin systems

Liquid crystalline epoxy resin (LCE) modify cyanate ester/epoxy resin blend systems were studied by scanning electron microscope, polarizing optical microscope, thermogravimetric analyzer, differential scanning calorimetry, thermal mechanical analysis, and rheometers. With the addition of LCE resin, the blends showed both an enhanced curing rate and increased glass transition temperature of cured samples. The phase structures of the blends changed from homogenous to liquid crystalline phase when the content of LCE was increased. At the same time, the mechanical properties were also improved and thermal expansion coefficients were lowed down. The thermal degradation temperatures showed little differences, while the residue char yields were slightly increased with the addition of LCE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Liquid crystalline epoxy resin modified cyanate ester for high performance electronic packaging

A high performance modified cyanate ester (CE) resin system with significantly improved toughness, water resistance and dimensional stability was developed by copolymerizing CE resin with liquid crystalline epoxy resin (LCE) for electronic packaging. Four LCE/CE resins with different contents of LCE were prepared to systemically evaluate the effect of the content of LCE on the key properties of the modified system such as mechanical, dielectric and thermal properties as well as water resistance. Results reveal that the addition of LCE to CE can not only decrease the curing temperature of CE, but also significantly improve the integrated properties including mechanical and dielectric properties, thermal resistance as well as water resistance of cured resin. For example, compared with the whole exothermic peak of CE, that of LCE10/CE significantly shifts toward low temperature with a gap of about 15°C. On the other hand, the impact strength of cured LCE10/CE resin (22 kJ/m²) is about 2.1 times of that of CE resin; while the water absorption of the former is only 81.2% of that of the latter. In addition, cured LCE/CE resins also exhibit lower and more stable dielectric loss than CE resin over the whole frequency range from 10 to 10⁶ Hz. All these improvements in macro-performance by the addition of LCE to CE resin are not only ascribed to the cross-linked chemical structure, but also attributed to the rigid structure of liquid crystalline resin. The outstanding integrated properties of LCE/CE resins suggest great potential to be applied in the field of high performance electronic packaging.     

A simple imide compound as a curing agent for epoxy resin. I. Synthesis and properties

A simple imide compound, 4‐amino‐phthalimide (APH), was synthesized as a curing agent for epoxy resin. APH was prepared from the hydration of 4‐nitro‐phthalimide, which was prepared from the nitration of phthalimide. The chemical structure of APH was verified by IR and ¹H‐NMR spectra. The thermal properties and dielectric constant (ε) of a phosphorus‐containing novolac epoxy resin cured by APH were determined and compared with those of epoxy resins cured by either 4,4′‐diamino diphenyl methane (DDM) or 4,4′‐diamino diphenyl sulfone (DDS). The results indicate that the epoxy resin cured by APH showed better thermal stability and a lower ε than the polymer cured by either DDM or DDS. This was due to the introduction of the imide group of APH into the polymer structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhancement in the thermal and dynamic mechanical properties of high performance liquid crystalline epoxy composites through uniaxial orientation of mesogenic on carbon fiber

In this work, a high performance liquid crystalline epoxy composite was prepared and the effect of the alignment of LCE with long lateral substituent on the carbon fiber surface curing at low temperature on fracture toughness, dynamic mechanical, and thermal properties of liquid crystalline epoxy with lateral substituent (LCE6) was investigated by polarized optical microscopy (POM), wide angle X‐ray diffraction measurements (WAXS), dynamic mechanical analysis (DMA), thermogravimetric (TGA), and scanning electron microscopy (SEM). Curing degree of the composite was observed by FTIR. The experimental results indicate that the fracture toughness, glass transition temperature (T_g), thermal stability, degradation kinetics are associated with the alignment of LCE6 along long axis of carbon fiber. The alignment of LCE6 on carbon fiber surface can increase mesogen network density, which leads to higher fracture toughness, higher thermal stability, increase of the activation energies and higher T_g of the composite. The dynamic mechanical analysis shows that the compoaite possesses extremely higher dynamic storage moduli, which indicates that this LCE6/DDM/CF composite can be a high performance composite. Thus, the compoaite can be a potential candidate for advanced composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40363.     

Structure and properties of novel epoxy resins containing naphthalene units and aliphatic chains

Two novel epoxy resins; namely, R1 and R2 were synthesized and characterized. These two resins were isomers and both contained naphthalene units and two symmetric flexible aliphatic ester chains terminated by epoxy groups. To investigate the influence of different structural isomers on the performance of these epoxy resins, they were both cured with various curing agents which results in the choosing of 4,4′-diaminodiphenylmethane (DDM) as the optimized curing agent. The curing technical temperature was obtained from extrapolated plots of T–β curve at different heating rates. The kinetic parameters, the activation energy (E _a) and the reaction order (n) were deduced by Kissnger’s isoconversional method and Crane equation. The moisture absorption and mechanical and thermal properties of the cured epoxy resins were investigated. Experimental results indicated that the R1/DDM and R2/DDM epoxy resins displayed improved mechanical performance without significant decrease in their important inherent properties, e.g., temperature of glass transition (T _g), moisture absorption and thermal properties when compared with the corresponding commercial biphenyl-type epoxy resins. The average inter-segment distances in R1/DDM and R2/DDM systems were 4.46 and 4.88 Å, respectively, which were measured by wide-angle X-ray diffraction. The result showed R1/DDM (1,5-di-substituted) was strongly hindered in comparison with R2/DDM (2,7-di-substituted) and E _a and T _g values of the R1/DDM were slightly higher than those of R2/DDM. Furthermore, mechanical properties and moisture absorption of the R1/DDM were lower than those of R2/DDM. Nevertheless, the position of the substituent only weakly affected the thermal properties and the reaction order (n).     

Epoxy resin based on 4,4′-dihydroxydiphenysulfone. I. Synthesis and reaction kinetics with 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenylsulfone

Epoxy resins based on 4,4′-dihydroxydiphenylsulfone (DGEBS) and diglycidyl ether of bisphenol A (DGEBA) were prepared by alkaline condensation of 4,4′-dihydroxydiphenylsulfone (bisphenol S) with epichlorohydrin and by recrystallization of liquid, commercial bisphenol A-type epoxy resin, respectively. Curing kinetics of the two epoxy compounds with 4,4′-diaminodiphenylmethane (DDM) and with 4,4′-diaminodiphenylsulfone (DDS) as well as T_g values of the cured materials were determined by the DSC method. It was found that the ? SO₂? group both in the epoxy resin and in the harener increases T_g values of the cured materials. DGEBS reacts with the used hardeners faster than does DGEBA and the curing reaction of DGEBS begins at lower temperature than does the curing reaction of DGEBA when the same amine is used. © 1994 John Wiley & Sons, Inc.     

Formation of Liquid Crystalline Order and Its Effect on Thermal Conductivity of AlN/Liquid Crystalline Epoxy Composite

The liquid crystalline (LC) order was introduced on aluminum nitride particles by the surface effect to increase the thermal conductivities of aluminum nitride/LC epoxy composites. X-ray diffraction and grazing incidence small-angle X-ray scattering analyses revealed that the LC epoxy resin cured on the surface of an α-Al₂O₃ substrate formed homeotropically aligned smectic layers to increase the thermal conductivity. Therefore, thermally treated aluminum nitride particles, which formed α-Al₂O₃ layers on their surfaces, were applied to prepare the composites with high thermal conductivity. The thermal conductivities of the resulting composites were 11–36% higher than those with the composites prepared using untreated aluminum nitride particles.     

A new Al2O3 porous ceramic prepared by addition of hollow spheres

A method for making porous ceramic prepared by adding hollow spheres was developed, and the resulting porous ceramic was named as hollow spheres ceramic. Water soluble epoxy resin was used as a gel former in the gelcasting process of the Al₂O₃ hollow sphere and Al₂O₃ powder, the porous ceramic porosity varies from 22.3 to 60.1 %. The influence of amount of Al₂O₃ hollow sphere and sintering temperature on the microstructure, compressive strength and thermal conductivity were investigated. With an increasing amount of hollow sphere in the matrix, the porosity increases, which leads to decreased bulk density, compressive strength and thermal conductivity. The compressive strength of the porous ceramics has a power law relation with the porosity, and the calculated power law index is 4.5. The equations of the relationship between porosity and thermal conductivity of porous ceramics are proposed. The thermal conductivity of samples with 60.1 % porosity is as low as 2.1 W/m k at room temperature.     

Preparation and construction mechanism of thermal conductive epoxy-based composite via magnetic field induced orientation

BN was modified with Fe₃O₄ to confer it with paramagnetic responsivity. The scanning electron microscopy and energy dispersive spectrometer (EDS) results demonstrated that with the assistance of an external magnetic field, the paramagnetic BN particles within an epoxy matrix are effectively aligned along the direction of the magnetic field during the curing process of epoxy resin, hence forming continuous thermal conduction pathways. Therefore, the thermal conductivity of the epoxy-based composite filled with 30 wt% of BN and externally applied with a 50 mT magnetic flux density was 0.7417 (W/m·K), an improvement of 207.89% relative to the pure epoxy resin. The establishment of continuous thermal pathways facilitates effective phonon conduction, thereby further enhancing the thermal conductivity of the material. Meanwhile, this study investigates the chain formation mechanism of Fe₃O₄-modified BN under the influence of a magnetic field. When subjected to an applied magnetic field, the magnetic BN embedded in an epoxy resin matrix undergoes magnetization, rotation, and contact. Subsequently, multiple particles initially form short chains, then aggregate into longer chains aligned with the direction of the magnetic field. The findings indicate that the magnetic field induced particle alignment method holds significant potential in the fabrication of high thermal conductivity polymer composites with low filler loading.     

溴化马来松香环氧树脂的制备及阻燃性

以马来松香和液溴为原料,合成了溴化马来松香;再与环氧氯丙烷发生酯化反应、闭环反应,合成了溴化马来松香环氧树脂。结果表明,在适宜的条件下,合成的环氧树脂的环氧值为0.30 mol·（100 g）^-1。 用红外光谱（FT-IR）、核磁共振谱（¹H NMR）和元素分析法对产物进行了表征。采用固化剂4,4′–二氨基二苯甲烷（DDM）对产物进行了固化。实验证明,溴化马来松香环氧树脂固化物具有较好的阻燃性。     

Design and preparation of low-filled magnetic oriented BN@Fe3O4/EP insulating composite with improved thermal conductivity and thermal stability

As an excellent two-dimensional insulating material with high thermal conductivity, high temperature stability and high hardness, hexagonal boron nitride(h-BN) is widely applied in semiconductor manufacturing, aerospace, metallurgical manufacturing and other cutting-edge fields. However, the unique surface structure of h-BN leads to poor lubricity and easy agglomeration, which limits the application of h-BN especially in the field of electronic packaging. To address key issues boosted above, this study designed and prepared the BN@Fe₃O₄ magnetic insulating particles and doped it into the reduced viscosity epoxy resin to prepare the composites. By selecting appropriate external magnetic field strength and BN@Fe₃O₄ particles’ content, a novel 3D structure of fillers like dominoes in epoxy resin composite was successfully constructed. The microstructure of the BN@Fe₃O₄ particles and composites were analyzed, the thermal conductivity, the mechanical and the electrical properties of composites were simultaneously tested. Results manifested that the core-shell structures with BN as core and Fe₃O₄ as shell was successfully prepared, linking through the PDA middle layer between the BN core and Fe₃O₄ shell. Under the influence of magnetic orientation, the BN@Fe₃O₄ magnetic particles were preferred an out-of-plane oriented in the epoxy resin composites, resulted an enormously enhanced on thermal conductivity of composites. At a magnetic field strength of 60 mT and 25 vol% BN@Fe₃O₄ content, the thermal conductivity of BN@Fe₃O₄/EP composites is as lofty as 1.832 W/(m K), which is 1023.46% higher than that of pure epoxy resin. Meanwhile, the thermal stability has also been slightly improved, the elastic modulus and insulation performances remain at the same level.     

Phthalonitrile‐epoxy blends: Cure behavior and copolymer properties

Binary blends composed of 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl (biphenyl PN) and diglycidyl ether of bisphenol A (epoxy resin) and oligomeric n = 4 phthalonitrile (n = 4 PN) and epoxy resin were prepared. The cure behavior of the blends was studied under dynamic and isothermal curing conditions using differential scanning calorimetry, simultaneous thermogravimetric/differential thermal analysis, infrared spectroscopy, and rheological analysis. The studies revealed that phthalonitrile‐epoxy blends exhibited good processability and that they copolymerized with or without the addition of curing additive. In the absence of curing additive, the blends required higher temperatures and longer cure times. The thermal and dynamic viscoelastic properties of amine‐cured phthalonitrile‐epoxy copolymers were examined and compared with those of the neat epoxy resin. The properties of the epoxy resin improved with increasing biphenyl PN content and with n = 4 PN addition. Specifically, the copolymers exhibited higher glass transition temperatures, increased thermal and thermo‐oxidative stabililty, and enhanced dynamic mechanical properties relative to the commercially available epoxy resin. The results showed that the phthalonitrile‐epoxy blends and copolymers have an attractive combination of processability and high temperature properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Epoxy resin containing the poly(sily ether): Preparation,morphology, and mechanical properties

The poly(sily ether) with pendant chloromethyl groups (PSE) was synthesized by the polyaddition of dichloromethylsilane (DCM) and diglycidylether of bisphenol A (DGEBA) with tetrabutylammonium chloride (TBAC) as a catalyst. This polymer was miscible with diglycidyl ether of bisphenol A (DGEBA), the precursor of epoxy resin. The miscibility is considered to be due mainly to entropy contribution because the molecular weight of DGEBA is quite low. The blends of epoxy resin with PSE were prepared through in situ curing reaction of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of PSE. The DDM‐cured epoxy resin/PSE blends with PSE content up to 40 wt % were obtained. The reaction started from the initial homogeneous ternary mixture of DGEBA/DDM/PSE. With curing proceeding, phase separation induced by polymerization occurred. PSE was immiscible with the 4,4′‐diaminodiphenylmethane‐cured epoxy resin (ER) because the blends exhibited two separate glass transition temperatures (T_gs) as revealed by the means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). SEM showed that all the ER/PSE blends are heterogeneous. Depending on blend composition, the blends can display PSE‐ or epoxy‐dispersed morphologies, respectively. The mechanical test showed that the DDM‐cured ER/PSE blend containing 25 wt % PSE displayed a substantial improvement in Izod impact strength, i.e., epoxy resin was significantly toughened. The improvement in impact toughness corresponded to the formation of PSE‐dispersed phase structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 505–512, 2003     

Synthesis and properties of trifluoromethyl groups containing epoxy resins cured with amine for low Dk materials

The study synthesized a trifluoromethyl (CF₃) groups with a modified epoxy resin, diglycidyl ether of bisphenol F (DGEBF), using environmental friendly methods. The epoxy resin was cured with 4,4′‐diaminodiphenyl‐methane (DDM). For comparison, this study also investigated curing of commercially available diglycidyl ether of bisphenol A (DGEBA) with the same curing agent by varying the ratios of DGEBF. The structure and physical properties of the epoxy resins were characterized to investigate the effect of injecting fluorinated groups into epoxy resin structures. Regarding the thermal behaviors of the specimens, the glass transition temperatures (T_g) of 50–160°C and the thermal decomposition temperatures of 200–350 °C at 5% weight loss (T_d5%) in nitrogen decreased as amount of DGEBF increased. The different ratios of cured epoxy resins showed reduced dielectric constants (D_k) (2.03–3.80 at 1 MHz) that were lower than those of pure DGEBA epoxy resins. Reduced dielectric constant is related to high electrronegativity and large free volume of fluorine atoms. In the presence of hydrophobic CF₃ groups, the epoxy resins exhibited low moisture absorption and higher contact angles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization, and thermomechanical properties of liquid crystalline epoxy resin containing ketone mesogen

This study focuses on the synthesis of a novel liquid crystalline epoxy resin (LCER) based on ketone mesogenic group. The chemical structure, melting range, and liquid‐crystalline phase transition behavior of the LCER were characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectroscopy, differential scanning calorimetry (DSC), and polarized optical microscopy (POM). Two endothermal peaks and one exothermal peak appeared in the DSC curves. A birefringent liquid crystalline texture was observed with POM during heating. The curing reaction of the LCER was monitored by DSC using diaminodipheylmethane (DDM) and diaminodiphenylsulfone (DDS) as curing agents, respectively. The results showed that the curing reaction of LCER/DDM proceeded faster than that of LCER/DDS in the initial stage. Birefringence was observed with POM during the curing processes. The results of thermomechanical properties showed that the glass transition temperatures of the cured LCERs were higher than 230°C, and that the LCER crosslinked networks were thermally stable up to 360°C. The LCER crosslinked networks showed much higher glass transition temperature, storage modulus, and thermal conductivity, and a lower coefficient of thermal expansion both in the glassy region and the rubbery region compared to those of a common epoxy resin (diglycidyl ether of bisphenol A). POLYM. ENG. SCI., 57:424–431, 2017. © 2016 Society of Plastics Engineers     

碳纳米管-膨胀石墨/环氧树脂复合材料的导热性能

在环氧树脂中添加多壁碳纳米管和膨胀石墨作为填料,以提高环氧树脂的导热性能. 结果表明,添加0.5wt%多壁碳纳米管时,环氧树脂的最佳导热系数为0.3448 W/(m?K),比不添加时提高30%;添加0.75wt%羧基改性多壁碳纳米管时,环氧树脂的最佳导热系数为0.3813 W/(m?K),比添不加时提高40%;同时添加多壁碳纳米管和膨胀石墨后,环氧树脂导热系数可进一步提高到0.4039 W/(m?K),表明在环氧树脂中添加混合填料,二者可在环氧树脂中形成有效的导热网络,能进一步提高聚合物的导热性能.