Effect of anhydride curing agents,imidazoles, and silver particle sizes on the electrical resistivity and thermal conductivity in the silver adhesives of LED devices

This study investigated the preparation of silver adhesives applied to a light‐emitting diode (LED) device as die‐attach materials consisting of silver particles, on epoxy resin, curing agents, and accelerants for complete curing at 150 °C for 30 min. For the epoxy resin, this study used 3,4‐epoxycyclohexyl‐methyl‐3,4‐epoxycyclohexanecarboxylate mixed with different types of anhydride curing agents such as 4‐methylcyclohexane‐1,2‐dicarboxylic anhydride and hexahydrophthalic anhydride as well as imidazole accelerants such as 2‐ethyl‐4‐methyl‐1H‐imidazole‐1‐propanenitrile, 2‐phenylimidazole, 2‐methylimidazole, 2‐phenyl‐2‐imidazoline, and 1,2‐dimethylimidazole. In addition, different size of silver particles and hybrid silver particles were used for the electrical resistivity and thermal conductivity of silver adhesives. Differential scanning calorimetric (DSC) measured conversion of silver adhesives based on different types and contents of the curing agents and accelerants under heating. The silver particles' distribution of silver adhesive also affected electrical resistance, as proved by scanning electronic microscopy (SEM) and four‐point probe. The obtained results showed that the silver adhesive containing an 100 wt % of epoxy resin mixed with 85 wt % of hexahydrophthalic anhydride, 1.0 wt % (weight of epoxy resin) of 2‐ethyl‐4‐methyl‐1H‐imidazole‐1‐propanenitrile, and 80 wt % (weight of epoxy resin) of hybrid silver particles (40 wt % 15 μm and 40 wt % 1.25 μm) was perfect, having the lowest electrical resistivity at 1.11 × 10^?4 Ω·cm and good thermal conductivity at 3.2 W/m·K. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43587.     

Influences of different gravity environments on the curing process and cured products of carbon‐nanotube‐reinforced epoxy composites

The influences of different gravity environments on the curing process and the cured products of carbon‐nanotube‐reinforced epoxy composites were investigated in this study. Different gravity environments were simulated with a superconducting magnet on the basis of which resin matrix composites with different amino‐functionalized multiwalled carbon nanotube (NH₂‐MWCNT) concentrations of 0.1, 0.3, 0.5, and 1 wt % were tested. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, thermomechanical analysis (TMA), thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and three‐point bending tests were used to analyze the characteristics of different curing processes and cured products. From the results, we observed that the curing rate of the epoxy composites was influenced by different gravity values, and there was anisotropy in the NH₂‐MWCNT‐reinforced epoxy composites cured in the simulated microgravity environment. More effects of gravity on the curing process and cured products could be obtained through detailed experiments and discussion; this is important and fundamental for improving and enhancing the properties of composite materials used in different gravity environments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41413.     

Study of dynamically cured PP/MAH‐g‐PP/talc/epoxy composites

In the present study, an epoxy resin was dynamically cured in a polypropylene (PP)/maleic anhydride–grafted PP (MAH‐g‐PP)/talc matrix to prepare dynamically cured PP/MAH‐g‐PP/talc/epoxy composites. An increase in the torque at equilibrium showed that epoxy resin in the PP/MAH‐g‐PP/talc composites had been cured by 2‐ethylene‐4‐methane‐imidazole. Scanning electron microscopy analysis showed that MAH‐g‐PP and an epoxy resin had effectively increased the interaction adhesion between PP and the talc in the PP/talc composites. Dynamic curing of the epoxy resin further increased the interaction adhesion. The dynamically cured PP/MAH‐g‐PP/talc/epoxy composites had higher crystallization peaks than did the PP/talc composites. Thermogravimetric analysis showed that the addition of MAH‐g‐PP and the epoxy resin into the PP/talc composites caused an obvious improvement in the thermal stability. The dynamically cured PP/MAH‐g‐PP/talc/epoxy composites had the best thermal stability of all the PP/talc composites. The PP/MAH‐g‐PP/talc/epoxy composites had better mechanical properties than did the PP/MAH‐g‐PP/talc composites, and the dynamically cured PP/MAH‐g‐PP/talc/epoxy composites had the best mechanical properties of all the PP/talc composites, which can be attributed to the better interaction adhesion between the PP and the talc. The suitable content of epoxy resin in the composites was about 5 wt %. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis,characterization, and properties of acrylate‐modified tung‐oil waterborne insulation varnish

An acrylate‐modified tung‐oil waterborne insulation varnish was synthesized from tung oil, maleic anhydride, and acrylates via a Diels–Alder reaction and free‐radical polymerization, and the varnish could be solidified at a relatively low temperature with blocked hexamethylene diisocyanate as a curing agent. The resulting films were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The insulation properties (electrical insulation strength, volume resistivity, and surface resistivity) of the varnish films were tested, and the resistances of films to salted water were evaluated. With an increase in the maleic anhydride content, the thermal stability of the film was improved, whereas the electrical insulation strength, volume resistivity, and surface resistivity decreased. The electrical insulation strength of the film after it was immersed in the NaCl solution was lower than that in dry state, and it decreased as the immersed time was prolonged. In particular, the electrical insulation strength loss of the film increased significantly at maleic anhydride contents beyond 25 wt %. Furthermore, the hardness of the film increased with increasing methyl methacrylate/N‐butyl acrylate ratio, whereas the flexibility and adhesion of film decreased to a certain degree at the same time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41608.     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of conductive polyaniline/epoxy composite

Conductive PANI (polyaniline)/epoxy composites were prepared by curing of the premix of PANI, which was synthesized in a multiple sulfonic acid system containing toluenesulfonic acid and dodecylbenzenesulfonic acid, and epoxy resin with methyl tetrahydrogen phenyl anhydride/triethylamine. The effects of the loadings of the curing agent, the accelerants as well as their types, and the PANI on the conductivities of the composites were studied. With increasing loadings of curing agent, conductivities of the composites increased first and decreased then, which is a synergistic effect of the PANI loading and its doping states. Under relatively lower loading of accelerant, conductivities of the composites increased with increase of PANI loading, whereas with higher loading of accelerant, the conductivities were affected by both the PANI and the accelerant loadings. Conductivity as high as 3 × 10⁻⁵ S/cm was achieved for curing of the composite containing 7.5 wt% of PANI and 4 wt% of accelerant at 80°C, which is suffice in application of electrostatic discharging. POLYM. COMPOS. 27:201–204, 2006. © 2006 Society of Plastics Engineers     

Intercalation and exfoliation of clay nanoplatelets in epoxy‐based nanocomposites: TEM and XRD observations

Diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) reinforced with organo‐montmorillonite clay nanoplatelets were investigated using anhydride‐ and amine‐curing agents. The sonication technique was used to process epoxy/clay nanocomposites. The basal spacing of clay nanoplatelets was observed by wide‐angle X‐ray scattering (WAXS), small‐angle X‐ray scattering (SAXS) techniques, and transmission electron microscopy. It was found that the basal spacing of clay nanoplatelets in epoxy matrix was expanded after mixing with either DGEBA/DGEBF or methyltetrahydrophthalic‐anhydride (MTHPA) curing agent. The sonication technique provided larger d‐spacing of clay nanoplatelets. Because of the different curing temperatures, MTHPA‐cured epoxy/clay nanocomposites produced more expanded d‐spacing of clay nanoplatelets modified with methyl, tallow, bis(2‐hydroxyethyl) quaternary ammonium (MT2EtOH) than triethylenetetramine‐cured nanocomposites. Depending on the selection of curing agent and organic modification for clay nanoplatelets, the d‐spacing was expanded to be up to 8.72 nm. POLYM. ENG. SCI., 46:452–463, 2006. © 2006 Society of Plastics Engineers     

Preparation and properties of epoxy‐modified tung oil waterborne insulation varnish

This work aimed to develop a novel epoxy‐modified tung oil waterborne insulation varnish with blocked hexamethylene diisocyanate as a curing agent. The Diels–Alder reaction between tung oil and maleic anhydride, and the ring‐opening esterification reaction of epoxy resin were confirmed. The conversion rate of epoxy was explored as a function of reaction time and temperature. The effects of epoxy resin content on the thermal stability, water absorption and insulation properties (insulation strength, volume resistivity, and surface resistivity) of films were investigated, and the resistances of films to salted water were evaluated. The increase in epoxy resin contents could improve the thermal stability and insulation properties of films, and decreased the water adsorption of films, but when the epoxy resin content reached 30% and above, the water solubility of resin became poor. After being immersed in 3.5 wt % NaCl solution, the electrical insulation strength of films were lower than that in dry state, and decreased as the immersed time prolonged. In particular, the electrical insulation strength loss of films increased significantly for epoxy resin content at 15% and below. Furthermore, the increase of epoxy resin content could improve the hardness and adhesion of films, but the flexibility of films became worse. On the basis of experimental, the epoxy resin content at 25% was appropriate to prepare waterborne epoxy‐modified tung oil resin. The resulting varnish may have potential as an immersing insulation varnish for the spindle of electric motor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42755.     

Synthesis of rosin‐based flexible anhydride‐type curing agents and properties of the cured epoxy

BACKGROUND: Although rosin acid derivatives have received attention in polymer synthesis in recent years, to the best of our knowledge, they have rarely been employed as epoxy curing agents. The objective of the study reported here was to synthesize rosin‐based flexible anhydride‐type curing agents and demonstrate that the flexibility of a cured epoxy resin can be manipulated by selection of rosin‐based anhydride‐type curing agents with appropriate molecular rigidity/flexibility. RESULTS: Maleopimarate‐terminated low molecular weight polycaprolactones (PCLs) were synthesized and studied as anhydride‐type curing agents for epoxy curing. The chemical structures of the products were confirmed using ¹H NMR spectroscopy and Fourier transform infrared spectroscopy. Mechanical and thermal properties of the cured epoxy resins were studied. The results indicate that both the epoxy/anhydride equivalent ratio and the molecular weight of PCL diol play important roles in the properties of cured resins. CONCLUSION: Rosin‐based anhydride‐terminated polyesters could be used as bio‐based epoxy curing agents. A broad spectrum of mechanical and thermal properties of the cured epoxy resins can be obtained by varying the molecular length of the polyester segment and the epoxy/curing agent ratio. Copyright © 2009 Society of Chemical Industry     

Compatibilization of polyethylene/polyaniline blends with polyethylene‐graft‐maleic anhydride

The use of compatibilizers as interfacial agents in composites can offer a convenient way to improve the mechanical properties of immiscible polymer blends. The aim of this article is to illustrate the compatibilization effect of polyethylene‐graft‐maleic anhydride (PEgMA) in blends of low‐density polyethylene (LDPE) and n‐dodecylbenzene sulfonate doped polyaniline (PANIDBSA) prepared by extrusion. Films with different compositions of the coupling agent were evaluated with optical spectroscopy and thermomechanical, electrical, mechanical, and morphological techniques. The incorporation of PEgMA into the LDPE/PANIDBSA composites resulted in an improvement of their electrical conductivity and changes in the mechanical and morphological properties of the films. When 5 wt % of the coupling agent was added to a 30 wt % of the polyaniline‐containing film, the conductivity increased by more than three orders of magnitude, and the ductility also improved qualitatively. The morphology analysis also indicated that the addition of PEgMA produced a strengthening of the filler–matrix interfacial region. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

固化剂对环氧包封料性能的影响

研究了以甲基四氢苯酐和间苯二胺作固化剂时 ,环氧树脂包封料的固化放热现象 ,测定了不同固化剂体系的包封料力学性能、电性能、密度和吸水性。结果表明 ,间苯二胺的活性大于酸酐固化剂的活性 ,但填料的加入使胺固化的放热降低 ,酸酐固化的升高。胺固化的冲击强度较高 ,加入填料可提高拉伸强度。胺固化的介电常数 ,介电损耗角较高 ,但体积电阻率较低 ,其吸水性较高     

Studies on the properties of glass fiber reinforced epoxy composites of DGEBA / epoxidized polyhydric alcohols with or without fortifier

Differential scanning calorimetry (DSC) technique was used to study the curing reaction of diglycidyl ether of bisphenol A (DGEBA) resin and different di- and trifunctional polyhydric alcohols with phthalic anhydride as curing agent and triethylamine as catalyst with or without fortifier. The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied as well. Activation energies of curing reactions range within 75.1 to 88.3 kJ mol^?1. The cured products have good thermal stability; the composites have good mechanical strength, electrical insulation properties and chemical resistance. 36 to 53% improvement in flexural strength has been observed when fortifier was added to the DGEBA-diluent systems.     

Study on the curing reaction,dielectric and thermal performances of epoxy impregnating resin with reactive silicon compounds as new diluents

Two silicon compounds including (3‐glycidoxypropyl)trimethoxysilane (A187) and (3‐glycidoxypropyl)methyldiethoxysilane (W78) were used and studied as reactive diluents for aluminum (III) acetylacetonate (Alacac) accelerated epoxy/anhydride impregnating resin systems. The dielectric performances were studied and characterized by the dielectric dissipation factor, dielectric constant, volume resistivity, and breakdown strength. The curing behaviors and thermal properties of the cured impregnants were studied by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry. The activation energies of different epoxy formulations were determined with Kissinger method. The results showed that W78 was effective to decrease the viscosity and had little influence on the curing reaction. The cured sample of 15 parts‐of‐W78‐containing‐epoxy resin/methyl‐hexahydrophthalic anhydride (MHHPA) accelerated by Alacac exhibits good dielectric and heat resistant performances with a dielectric dissipation factor below 0.04 at 155°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comparison of curing agents for epoxidized vegetable oils applied to composites

Interest in polymers from renewable sources, as alternatives to petroleum‐based polymers, remains strong; however, their performance must be acceptable. To improve performance of epoxidized vegetable oils (EVO) in composite matrix applications, five amine curing agents were evaluated and compared with an anhydride agent used previously. Curing agents were tested in matrices for composites containing a petroleum‐based epoxy resin plus 0% or 30% epoxidized oil from canola (ECO) and soybean (ESO). The two amines with the highest glass transition temperature, determined by differential scanning calorimetry, were selected for characterization by dynamic mechanical analysis; bis (p‐aminocyclohexyl) methane (PACM) showed the highest performance. Amine: epoxy ratios 0.6 to 1.6 were then evaluated; ratios of 0.8 and 1.0 showed superior performance. E‐glass fiber reinforced composites with PACM/EVO showed thermal and mechanical performance slightly lower than the composites with 0% EVO and comparable with those of the anhydride curing agent. Therefore, ECO or ESO blended with petroleum‐based epoxy resins cured with PACM are recommended for its application in E‐glass reinforced composites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Epoxy/imidazolium-based ionic liquid systems: The effect of the hardener on the curing behavior,thermal stability,and microwave absorbing properties

A new transparent microwave absorbing coating was developed by compounding 1-butyl-3-methyl imidazolium tetrafluoroborate (bmim.BF₄) ionic liquid (IL) with diglycidyl ether of bisphenol A-type epoxy resin. The systems were crosslinked with the IL alone or combined with conventional hardeners, as anhydride or aromatic amine. The curing behavior was investigated by thermal and spectroscopic analysis performed at high temperatures. Neat bmim.BF₄ was able to cure epoxy resin, giving rise to networks with outstanding thermal stability compared with the systems cured with anhydride or aromatic amine. bmim.BF₄ accelerated the curing process in the presence of aromatic amine but retarded this event when anhydride was used as an external curing agent. The glass-transition temperature evaluated by dynamic mechanical analysis decreased when the amount of IL increased, which can be attributed to side reactions during the curing process, as well as the plasticizing effect of IL. The epoxy networks cured with bmim.BF₄ alone or in combination with anhydride or aromatic amine were transparent and presented considerable microwave absorbing properties in the X-band frequency range (8–12 GHz), being the best performance observed for the systems cured with bmim.BF4/anhydride curing system, with reflection loss value around −16 dB at 11.3 GHz. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48326.     

Effects of chemical structure changes on thermal,mechanical, and crystalline properties of rigid rod epoxy resins

Effects of chemical structure changes on the thermal, mechanical, and crystalline properties of rigid rod epoxy resins have been studied for azomethine epoxy, biphenol epoxy, and tetramethyl biphenol epoxy. Rigid rod epoxies have exhibited better properties than those of the flexible bisphenol A epoxy. The chemical structures of both rigid rod epoxy and curing agent control the properties of cured rigid rod epoxies. When a flexible curing agent (methyl cyclohexane 1,2‐dicarboxylic anhydride) was used, the chemical structure of rigid rod epoxy has dominated effects on the properties. Thus, the azomethine epoxy has shown the best thermal and mechanical properties among three rigid rod epoxies. While a rigid curing agent (sulfanilamide) was used, the physical properties of cured epoxies are not only dependent on the chemical structures of epoxies but also on the ease of formation of ordered network. Among the cured rigid rod epoxies, only the biphenol epoxy cured by sulfanilamide exhibits a liquid crystalline network. It has the highest glass transition temperature (219°C) and the lowest coefficient of thermal expansion (20.8 μm/m°C). However, the most thermal stable system is azomethine epoxy cured with sulfanilamide. It has a weight loss (39%) at 450°C. Their excellent thermal and mechanical properties of rigid rod epoxies are useful in composites, printed wiring boards, integrated circuit encapsulations, etc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 446–451, 2000     

Use of eugenol and rosin as feedstocks for biobased epoxy resins and study of curing and performance properties

In this study, an epoxy based on eugenol and an anhydride curing agent based on rosin were prepared. Curing of the eugenol epoxy with a commercial anhydride curing agent and with the rosin‐derived anhydride curing agent was studied. For comparison, a commercial bisphenol A type epoxy, DER353, was also selected in the curing study. The syntheses of the eugenol epoxy and rosin anhydride were investigated and the chemical structures of the products and intermediates were characterized using ¹H NMR and Fourier transform infrared spectroscopies. Non‐isothermal curing of the eugenol epoxy with hexahydrophthalic anhydride and the rosin‐derived maleopimaric acid was studied using differential scanning calorimetry. Thermomechanical properties and thermal stability of the cured epoxy resins were evaluated using dynamic mechanical analysis and thermogravimetric analysis, respectively. Addition of 2‐ethyl‐4‐methylimidazole as catalyst greatly decreased the curing temperature and promoted the completion of cure reactions. The results suggest that the eugenol epoxy and the bisphenol A type epoxy have similar reactivity, dynamic mechanical properties and thermal stability. © 2013 Society of Chemical Industry     

Crosslinking and ozone degradation of thermosetting resins based on maleic anhydride/diene copolymer and polyfunctional alcohols

Crosslinking and de‐crosslinking reactions of an alternating copolymer of maleic anhydride (MAn) and 2,4‐dimethyl‐1,3‐pentadiene (DMPD) by thermal curing with polyfunctional alcohols as the crosslinkers and subsequent ozone degradation are reported in this article. The ring‐opening reaction of an anhydride group by polyfunctional alcohols produces network polymers with an ester linkage. The rate of crosslinking reaction depends on the curing conditions, i.e. the structure of the used alcohols and the curing temperature and time. The crosslinking density of the alcohol‐cured copolymers is low due to a slow reaction between the anhydride and hydroxy groups, being different from the corresponding epoxy‐cured copolymer with a dense network structure reported in a previous article. The insoluble resins are readily de‐crosslinked and solubilized by ozone degradation. The polymer surface modification by ozone is also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42763.     

Imidazolium and deep eutectic ionic liquids as epoxy resin crosslinkers and graphite nanoplatelets dispersants

Two types of ionic liquids (IL), i.e., molecular ionic 1‐butyl‐3‐methylimidazolium thiocyanate ([BMIM]SCN) and deep eutectic solvent (DES) based on choline chloride and tris(hydroxymethyl)propane, as well as their mixture have been used as epoxy resin curing agents. [BMIM]SCN showed the highest catalytic activity toward epoxy resin polymerization as compared to up today used ILs. Curing process of epoxy resin was investigated at ambient temperature (storage time up to more than 60 days) and elevated temperatures (80–200°C) using rheometry and DSC techniques. Thermomechanical analysis allowed to determine an influence of IL type and content on composites crosslinking density, glass transition temperature, and tan δ values. Graphite nanoplatelets (GNP) was dispersed in DES and then in DES/IL/epoxy resin composition prepared, cast, and cured to obtain nanocomposite material. Electrical volume resistivity of the nanocomposites with 0.25–1 wt % GNP increased with nanofiller content up to the highest value of 2.8 × 10⁶ Ω · cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40401.     

改进环氧固化物电性能的方法研究及应用进展

综述了近几年对环氧树脂电性能的改进研究进展,指出改性主要从5个方面:环氧树脂自身的改良、固化剂改性、促进剂改性、稀释剂改性、填料改性,经过改性后的环氧树脂,电性能更优良,用途更广泛。