• 한국전기전자재료학회논문지
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• 제32권1호
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• pp.6-12
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• 2019

Bonding properties of epoxy-containing solder joints were investigated by a high temperature aging test. Specimens were prepared by bonding an R3216 standard chip resistor to an OSP-finished PCB by a reflow process with two basic types of solder (SAC305 & Sn58Bi) pastes and two epoxy-solder (SAC305+epoxy & Sn58Bi+epoxy) pastes. In all epoxy solder joints, an epoxy fillet was formed in the hardened epoxy, lying around the outer edge of the solder joint, between the chip and the Cu pad. In order to analyze the bonding characteristics of solder joints at high temperatures, a high-temperature aging test at $150^{\circ}C$ was carried out for 14 days (336 h). After aging, the intermetallic compound $Cu_6Sn_5$ was found to have formed in the solder joint on the Cu pad, and the shear stress on the conventional solder joint was reduced by a significant amount. The reason that the shear force did not decrease much, even though in epoxy solder, was thatbecause epoxy hardened at the outer edge of the supported solder joints. Using epoxy solder, strong bonding behavior can be ensured due to this resistance to shear force, even in metallurgical changes such as those where intermetallic compounds form at solder joints.

• Carbon letters
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• 제22권
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• pp.36-41
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• 2017

Biodegradable epoxy (B-epoxy) was prepared from diglycidyl ether of bisphenol A and epoxidized linseed oil. The mechanical properties of B-epoxy composites reinforced with multi-walled carbon nanotubes (MWCNTs/B-epoxy) were examined by employing dynamic mechanical analysis, critical stress intensity factor ($K_{IC}$) tests, and impact strength tests. The electromagnetic interference shielding effectiveness (EMI-SE) of the composites was evaluated using reflection and absorption methods. Mechanical properties of MWCNTs/B-epoxy were enhanced with an increase in the MWCNT content, whereas they deteriorated when the MWCNT content was >5 parts per hundred resin (phr). This can likely be attributed to the entanglement of MWCNTs with each other in the B-epoxy due to the presence of an excess amount of MWCNTs. The highest EMI-SE obtained was ~16 dB for the MWCNTs/B-epoxy composites with a MWCNT content of 13 phr at 1.4 GHz. The composites (13 phr) exhibited the minimum EMI-SE (90%) when used as shielding materials at 1.4 GHz. The EMI-SE of the MWCNTs/B-epoxy also increased with an increase in the MWCNT content, which is a key factor affecting the EMI-SE.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.255-257
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• 2012

Epoxy resin without any hardener can harden in the presence of hydroxide ions in cement mortars and concretes at ambient temperature. The purpose of present study is to examine the hardening properties of hardener-free epoxy-modified mortars by curing conditions. The hardener-free epoxy-modified mortars using diglycidyl ether of A epoxy resin are prepared with various polymer-cement ratios, and subjected to initial moist/dry curing, initial steam(90℃) curing, initial steam/heat(80℃, 100℃) curing.As a result, degree of hardening of epoxy resin in initial moist/dry cured, initial steam cured and initial steam/heat(80℃) cured hardener-free epoxy-modified mortars is decreased with increasing polymer-cement ratio. However, it is markedly improved with additional dry-curing periods. On the other hand, regardless of the polymer-cement ratio and dry curing periods, degree of hardening of hardener-free epoxy-modified mortars with initial steam/heat(100℃) cure is over 95%.

• 수산해양기술연구
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• 제43권4호
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• pp.362-369
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• 2007

This paper was studied on the characteristics of acid resistance and thermal shock for epoxy coatings in the strong acidic environment. The exhaust gas system, such as a air preheater, desulfurization equipment, for industrial boiler is damaged by dew point corrosion. To protect the acid corrosion, the coating using nonmetal was applied. The electrochemical polarization test, acid resistance and thermal shock test for epoxy coatings were carried out. And the acid resistance and thermal shock characteristics, aspect, and electrochemical anti-corrosion characteristics for epoxy coatings in the strong acidic environment were considered. The main results are as followings: As the epoxy glass flake coating by acidic thermal shock was damaged to the crack, blistering and elution etc., the current density of epoxy glass flake coating is high. But the damage of epoxy metal complex coating by acidic thermal shock was not occurred. Therefore the characteristics of acid resistance and thermal shock for epoxy metal complex coating is better than those for epoxy glass flake coating.

• Carbon letters
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• 제15권1호
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• pp.32-37
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• 2014

Multi-walled carbon nanotube (MWCNT)/epoxy composites are prepared by a vacuum assisted resin transfer molding (VARTM) method. The mechanical properties, fracture surface morphologies, and thermal stabilities of these nanocomposites are evaluated for epoxy resins with various amounts of MWCNTs. Composites consisting of different amounts of MWCNTs displayed an increase of the work of adhesion between the MWCNTs and the matrix, which improved both the tensile and impact strengths of the composites. The tensile and impact strengths of the MWCNT/epoxy composite improved by 59 and 562% with 0.3 phr of MWCNTs, respectively, compared to the epoxy composite without MWCNTs. Thermal stability of the 0.3 phr MWCNT/epoxy composite increased compared to other epoxy composites with MWCNTs. The enhancement of the mechanical and thermal properties of the MWCNT/epoxy nanocomposites is attributed to improved dispersibility and strong interfacial interaction between the MWCNTs and the epoxy in the composites prepared by VARTM.

• 동력기계공학회지
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• 제14권6호
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• pp.83-88
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• 2010

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

• Advanced Composite Materials
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• 제17권2호
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• pp.167-175
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• 2008

Vapor grown carbon fibers (VGCF) were treated with atmospheric plasma enhancing the surface area in order to improve the bonding to the matrix in epoxy composites. The changes in the mechanical properties of VGCF/epoxy nanocompostes, such as tensile modulus and tensile strength were investigated in this study. VGCF with and without atmospheric plasma treatment for surface modification were used in this investigation. The interdependence of these properties on the VGCF contents and interfacial bonding between VGCF/epoxy matrix were discussed. The mechanical properties of atmospheric plasma treated (APT) VGCF/epoxy were compared with raw VGCF/epoxy. The tensile strength of APT VGCF/epoxy nanocomposites showed higher value than that of raw VGCF. The tensile strength was increased with atmospheric plasma treatment, due to better adhesion at VGCF/epoxy interface. The tensile modulus of raw VGCF and APT VGCF/epoxy matrix were of the similar value. The dispersion of the VGCF was investigated by scanning electron microscopy (SEM), SEM micrographs showed an excellent dispersion of VGCF in epoxy matrix by ultrasonic method.

• Advances in materials Research
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• 제1권1호
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• pp.93-107
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• 2012

Epoxy resin is widely used in high voltage apparatus as insulation. Fillers are often added to epoxy resin to enhance its mechanical, thermal and chemical properties. The addition of fillers can deteriorate electrical performance. With the new development in nanotechnology, it has been widely anticipated that the combination of nanoparticles with traditional resin systems may create nanocomposite materials with enhanced electrical, thermal and mechanical properties. In the present paper we have carried out a comparative study on dielectric properties, space charge and dielectric breakdown behavior of epoxy resin/nanocomposites with nano-fillers of $SiO_2$ and $Al_2O_3$. The epoxy resin (LY556), commonly used in power apparatus was used to investigate the dielectric behavior of epoxy resin/nanocomposites with different filler concentrations. The epoxy resin/nanocomposite thin film samples were prepared and tests were carried out to measure their dielectric permittivity and tan delta value in a frequency range of 1 Hz - 1 MHz. The space charge behaviors were also observed by using the pulse electroacoustic (PEA) technique. In addition, traditional epoxy resin/microcomposites were also prepared and tested and the test results were compared with those obtained from epoxy resin/nanocomposites.

• Macromolecular Research
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• 제10권6호
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• pp.332-338
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• 2002

The effect of an electron beam and ${\gamma}$-ray irradiation on the curing of epoxy resins was investigated. Diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) as epoxy resin were used. The epoxy resins containing 1.0-3.() wt% of triarylsulphonium hexafluoroantimonate(TASHFA) and triarylsulphonium hexafluorophosphate(TASHFP) as initiator were irradiated under nitrogen at room temperature with different dosage of EB and ${\gamma}$-rays from a Co$^{60}$ u source. The chemical and mechanical characteristics of irradiated epoxy resins were compared after curing of EB and ${\gamma}$-ray irradiation. The thermal properties of cured epoxy were investigated using dynamic mechanical thermal analysis. The chemical structures of cured epoxy were characterized using near infrared spectroscopy. Mechanical properties such as flexural strength, modulus were measured. The gel fraction of DGEBA with ${\gamma}$-ray was higher than that of the epoxy with EB at the same dose. Young's modulus of the sample irradiated by ${\gamma}$-ray is higher than that of sample cured by EB. From the result of strain at yield, it was found that the epoxy cured by ${\gamma}$-ray had a higher stiff property compared with the irradiated by EB.

• 비파괴검사학회지
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• 제34권2호
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• pp.119-127
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• 2014

An epoxy coating applied to the concrete surface of a containment building deteriorates in hazardous environments such as those containing radiation, heat, and moisture. Unlike metals, the epoxy coating on a concrete liner absorbs and discharges moisture during the degradations process, so it has a different density and volume during service. In this study, acoustic impedance was adopted for characterizing the degradation of a glass-reinforced epoxy coating using the acoustic reflection coefficient (reflectance) on a rough epoxy coating. For estimating the acoustic reflectance on a wavy epoxy coating surface, a probabilistic model was developed to represent the multiple irregular reflections of the acoustic wave from the wavy surface on the basis of the simulated annealing technique. A number of epoxy-coated concrete specimens were prepared and exposed to accelerated aging conditions to induce an artificial aging degradation in them. The acoustic impedance of the degraded epoxy coating was estimated successfully by minimizing the error between a waveform calculated from the mathematical model and a waveform measured from the surface of the rough coating.