• Current Research on Agriculture and Life Sciences
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• v.30 no.1
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• pp.41-50
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• 2012

As a part of abating formaldehyde emission of urea-formaldehyde resin, this study was conducted to investigate the rmalcure kinetics of both neat and modified urea-formaldehyde resins using differential scanning calorimetry. Neat urea-formaldehyde resins with three different formaldehyde/urea mol ratios (1.4, 1.2 and 1.0) were modified by adding three different additives (sodium bisulfite, sodium hydrosulfite and acrylamide) at two different levels (1 and 3wt%). An isoconversional method at four different heating rates was employed to characterize thermal cure kinetics of these urea-formaldehyde resins to obtain activation energy ($E{\alpha}$) dependent on the degree of conversion (${\alpha}$). The $E{\alpha}$ values of neat urea-formaldehyde resins (formaldehyde/urea = 1.4 and 1.2) consistently changed as the ${\alpha}$ increased. Neat and modified urea-formaldehyde resins of these two F/U mol ratios did show a decrease of the $E{\alpha}$ at the final stage of the conversion while the $E{\alpha}$ of neat urea-formaldehyde resin (formaldehyde/urea = 1.0) increased as the ${\alpha}$ increased, indicating the presence of incomplete cure. However, the change of the $E{\alpha}$ values of all urea-formaldehyde resins was consistent to that of the Ea values. The isoconversional method indicated that thermal cure kinetics of neat and modified urea-formaldehyde resins showed a strong dependence on the resin viscosity as well as diffusion control reaction at the final stage of the conversion.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.49-52
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• 2001

The investigation of cure kinetics, morphology, and fracture toughness studies on epoxy resin/amine terminated PEI/Anhydride system were performed by differential scanning calorimetry and scanning electron microscopy. Modified autocatalystic kinetics model was applied by isothermal scan test. The fracture toughness for the neat epoxy resin was 2.15 MPa m0.5 and the fracture toughness was improved 45% as neat epoxy resin system. The generation of secondary phase of AT-PEI was observed and its size was grown up by increasing contents of PEI.

• Journal of the Korean Graphic Arts Communication Society
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• v.24 no.1
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• pp.1-12
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• 2006

The rheological characteristics of an ink relate to its performance on the press and to the printing quality such as ink stability, transfer characteristics, mottle, squash, misting, dot gain, and so on. For lithographic print, the emulsification of ink is an important factor to determine the product. And also the rheological characteristics of the emulsified ink should be investigated. Thus, in this study, the effects of the changing molecular weight of rosin modified phenolic resin on the water-pickup ratio of neat inks were studied. And then rheological properties of neat inks and emulsified inks with changing molecular weight of rosin modified phenolic resin were analyzed by using rotational rheometer.

• Composites Research
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• v.24 no.2
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• pp.30-37
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• 2011

Analysis of wettability between epoxy resin and glass fabric was studied. The mixing ratios of epoxy resin and anhydride hardener were varied as 1:0.5, l:l and l:1.2. Catalyst content was fixed as 0.1wt% of the mixed resin. A curing analysis by differential scanning calorimeter(DSC) showed a possible impregnation of the mixed resin at the room temperature. An effective contact angle of the mixed epoxy resin drop onto the glass fabric being preset on a flat glass plate was measured as a function of time. The wet area of the epoxy resin drop was also measured. Behaviors of the contact angle, the droplet height, the neat wet area and the coefficient of wettability were used to evaluate the wettability of the epoxy resin onto the glass fabric. It was concluded that the equivalent ratio of 1: 1.2 was the most suitable for the wettability.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.89-92
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• 2012

The effect of organic impurities on the electrical properties of a neat epoxy resin was studied. 0.05, 0.5 and 1.0 phr of iso-propyl alcohol (IPA) and methylene chloride (MC) mixture (50/50 wt%) were used as impurities. The current density, volume resistance and impedance characteristics of the epoxy/IPA/MC systems were measured with a high voltage source meter and broadband dielectric spectroscopy. Glass transition temperature (Tg) was measured by a differential scanning calorimetry (DSC) and it was found that Tg decreased slightly with increasing IPA/MC content. It was also found that Tg values of the epoxy systems with various IPA/MC contents were closely related to the current density, volume resistance and impedance characteristics.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.12-18
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• 2017

Transparent organic-inorganic hybrid hard coating films were prepared by the addition of $SiO_2$ or $ZrO_2$, as an inorganic filler to improve the hardness property, filler was highly dispersed in the acrylic resin. To improve the compatibility in the acrylic resin, $SiO_2$ or $ZrO_2$ is surface-modified using various silanes with variation of the modification time and silane content. Depending on the content and kind of the modified inorganic oxide, transparent modified inorganic sols were formulated in acryl resin. Then, the sols were bar coated and cured on PET films to investigate the optical and mechanical properties. The optimized film, which has a modified $ZrO_2$ content of 4 wt% markedly improved in terms of the hardness, haze, and transparency as compared to neat acrylate resin and acrylate resin containing modified $SiO_2$ content of 8 wt%. Meanwhile, the low transparency and high haze of these films slowly appeared at $SiO_2$ content above 10 wt% and $ZrO_2$ content of 5 wt%, but the hardness values were maintained at 2H and 3H, respectively, in comparison with the HB of neat acrylate resin.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.31-34
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• 2005

Hygrothermal aging of the laminates of $Avimid^{R}$ K3B/IM7 in $80^{\circ}C$ water was studied as a function of immersion time prior to forming microcracks. The factors causing the $80^{\circ}C$ water to degradation of the laminates could be the degradation of the matrix toughness, change in residual stresses or interfacial damage between the fiber and matrix. The times to saturation in $80^{\circ}C$ water for the laminates and the neat resin are 100 hours and 500 hours. After 500 hours aging of the neat resin in $80^{\circ}C$ water, the glass transition temperature was changed less than $1\%$ by DSC test and the weight gain was $1.55\%$ increase. After 500 hours aging, the fracture toughness of the neat resin was decreased about $37\%$ by 3-point bending test. After 100 hours aging of the [+45/0/-45/90]s K3B/IM7 laminates in $80^{\circ}C$ water, the weight gain was $0.41\%$ increase. The $80^{\circ}C$ water diffusion rate into the neat resin was faster than into the laminates. In 100 hours, the loss of the microcracking toughness of the laminates was $28\%$ of the original toughness by our own microcracking fracture toughness criterion.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.147-150
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• 2002

The cure kinetics of blends of epoxy (DGEBA:diglycidyl ether of bisphenol A)/anhydride (NMA:nadic methyl anhydride) resin with synthesized amino terminated polyetherimide (AT-PEI) were studied using differential scanning calorimetry (DSC) and Dynamic Mechanical Analysizer(DMA) under isothermal condition to determine the reaction parameters and gel-vitrification behavior. The fracture toughness of AT-PEI 20phr/epoxy resin system was improved over 224% and 42.5% more than neat epoxy resin and commercial PEI/Epoxy Resin System.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.74-77
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• 2015

The cure kinetics of a neat epoxy system and epoxy/silica composite were investigated by DSC analysis. A cycloaliphatic type epoxy resin was diglycidyl 1,2-cyclohexanedicarboxylate and curing agent was anhydride type. To estimate kinetic parameters, the Kissinger equation was used. The activation energy of the neat epoxy system was 88.9 kJ/mol and pre-exponential factor was 2.64×10¹² min⁻¹, while the activation energy and pre-exponential factor for epoxy/silica composite were 97.4 kJ/mol and 9.21×10¹² min⁻¹, respectively. These values showed that the silica particles have effects on the cure kinetics of the neat epoxy matrix.

• Textile Coloration and Finishing
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• v.30 no.2
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• pp.98-106
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• 2018

In this study, graphene oxide(GO) was synthesized by using Hummer's method. Then, GO was used as a additive for epoxy resin nanocomposites that were prepared by mixing Tetraglycidyl diamino diphenyl methane(TGDDM) and hardner(MDEA+M-MIPA). Thermal and mechanical properties of epoxy resin nanocomposites were confirmed by analytical methods such as TG-DTA, DMA, fracture toughness, tensile strength, and flexural strength. The fracture surfaces of epoxy resin nanocomposites with different content of the GO were observed by a Scanning Electron Microscope(SEM). The mechanism for mechanical properties of epoxy resin nanocomposites was analyzed by modeling of nanocomposites with different GO weight. Due to the GO, both the heat resistance and the glass transition temperature of the epoxy resin nanocomposites were improved. Interestingly, when 0.1wt.% of GO was added to the epoxy resin/hardner mixture, the properties of mechanical increased compared with the neat epoxy resin. This results were caused by an aggregation between the GO.