• Composites Research
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• v.18 no.3
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• pp.47-52
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• 2005

Pultrusion process of phenolic foam composite is investigated. Phenolic foam composites provide heat and flame resistance with less weight. When made into foam, a variety of properties can be obtained with different bubble size and number density. In this study, effect of process variables on the foaming characteristics of phenolic resin composites during pultrusion process has been studied experimentally. The process variables considered are the heating temperature and the pulling speed as well as the mass fraction of blowing agent. Experiments were performed using a laboratory scale pultrusion apparatus. Optimal process condition was found by observing the micro-morphology.

• Journal of the Korean Chemical Society
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• v.33 no.6
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• pp.601-606
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• 1989

The effects of temperature and retaining ion on the separation factor (${\alpha}$) and distribution ratio (D) of some lanthanides ($Pr^{3+},\;Nd^{3+},\;Sm^{3+},\;and\;Er^{3+}$) have been studied in the EDTA solution as an elutant by using Amberite IR 120 + resin. The retaining ions on the resin were ${NH_4}^+,\;Na^+,\;K^+,\;Mg^{2+},\;Ca^{2+},\;Zn^{2+}$and $Ce^{3+}$. Separation factor of Nd/Pr is much improved by using $Ce^{3+}$ as retaining ion. The distribution ratios were decreased with the increase of temperature, but separation factors did not always increase with the increase of temperature. However, in the case of $Ce^{3+}$ as retaining ion, separation factors of Nd/Pr and Sm/Nd were increased with the increasing of temperature. And also in the case of $Zn^{2+}$ as retaining ion, separation factor of Er/Sm was increased with the increasing of temperature.

• Composites Research
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• v.19 no.4
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• pp.1-6
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• 2006

The effects of aging on fatigue of PSF/AS4 laminates tvas studied using the new energy release rate analysis. The analysis by the variational mechanics has been useful in providing fracture mechanics interpretation of matrix microcracking in cross-ply laminates. This paper describes the changes of the critical energy release rate ${\Delta}Gmc$(microcracking toughness) about the variation of the aging period during fatigue loading. The master plot by modified Pans-law gives a characterization of a material system's resistance to microcrack formation. PSF/AS4 $[0/902]_s$ laminates were aged at four different temperatures based on the glass transition temperature for 60 days. At all temperatures, the toughness decreased with aging time. The decrease of the toughness at higher temperature was faster than at lower temperature. To assess the effects of aging on fatigue, the unaged laminates were compared with the laminates which were aged for 60 days at $170^{\circ}C$ near $180^{\circ}C\;T_g$. The slope of dD/dN versus A 6u, of the aged laminates was lower than that of the unaged laminates. There was a significant shift of the aged data to formation of microcracks at the lower values of ${\Delta}G_m$.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1358-1364
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• 2019

The mechanical properties of Heavy duty resin of synthetic polyurethane-epoxy resin for stainless steel were measured by SEM, FT-IR, tensile properties, and specific mass loss by EIS analysis, etc. As interest in eco-friendly medium coatings increased, the Heavy duty coatings were synthesized for various metals such as stainless steel composed of Polyol, MDI, water bored Epoxy resin, filling agent, silicon surfactant, catalyst etc. The coatings of synthetic Heavy duty resin were increased tensile strength due to various temperature change, and the low-Specific Mass Loss was measured in a highly electrolytic solution. In conclusion, the Heavy Duty coatings composed of polyurethane and waterbored Epoxy resin were synthetic microstructure with cross linkage can be good material for coating of anticorrosion of metal substrates such as stainless steel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.371-372
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• 2008

본 논문은 새롭게 초음파 분산기법을 이용하여 제조된 나노콤포지트 와 원형에폭시 수지에 대한 전기적 특성인 트리현상의 여러특성을 연구하였다. 나노필러인 Layered Silicate Particles가 에폭시수지 중에 Power Ultrasonic으로 분산된 나노콤포지트를 제조하였다. 충진된 혼합물에서 나노입자의 영향을 조사하기위해 열적, 구조적 특성을 연구하였고, 장시간 절연파괴 특성을 조사하기위해 침대평판 전극으로 원형에폭시수지와 나노콤포지트와 비교 측정하였다. 연구는 에폭시원형수지에 대한 인가전압레벌(교류 10, 15, 20kV)의 변화와 온도변화에 대한 (30,90,$130^{\circ}C$)의 트리특성을 연구하였다. 모든 전압레벨에서는 일정전압까지 1kV/s 로 승압 후 일정하게 인가되었고, 파괴에 이를 때까지 측정한 결과 10kV, 15Kv, 20KV의 경우 1042,75,488분후에 파괴에 이르렀다. 그러나 트리진행속도는 인가전압이 높을수록 빠르게 진행하였다. 온도 변화에 대한 트리특성으로서 15kV인가 후 파괴에 이르는 시간은 30,90,$130^{\circ}C$의 경우 75.3, 970, 226분으로 $90^{\circ}C$의 경우 절연성능이 가장 우수하였고, 트리진전속도는 $30^{\circ}C,130^{\circ}C,90^{\circ}C$ 순으로 나타났다. 이는 트리진전으로 파괴에 이르는 시간과 속도는 트리형태에 지배적으로 영향을 맡고 있음을 알 수 있었다. 또한 나노콤포지트 트리의 경우 15kV인가시 10902에 파괴에 이르렀고, 트리진전속도는 0.000729mm/min으로 원형에 비하여 53.36배의 트리진전시간이 느리고, 파괴시간은 145배 오래 견디는 절연내력을 측정할 수 있었다.

• The Korean Journal of Rheology
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• v.9 no.4
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• pp.174-182
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• 1997

결정성 고분자수지는 가공조건에 의해 결정되는 미세구조의 변화에 따라 최종물성 이 현저히 달라지므로 최종 성형품의 물성을 극대화하기 위해서는 성형가공 중에 필연적으 로 부가되는 열이력 뿐만 아니라 전단이력이 결정화 거동에 미치는 영향을 규명하고 가공조 건의 최적화를 통하여 미세구조를 적절히 제어하는 것이 요구된다. 따라서 본 연구에서 in-situ 상태로 전단유도 결정화거동을 조사할수 있는 rheo-kinetic 실험 방법을 개발하고 결정화 거동에 미치는 열이력과 전단이력의 영향을 규명하고자 하였다. 이를 위해 비교적 결정화 속도가 빠른 폴리 부틸렌 테레프탈레이트 수지를 대상으로 냉각조건, 전단부가시간, 전단속도등을 다양하게 변화시키면서 plate-plate 레오미터로 시간에 따른 전단응력의 변화 를 조사하는 rheo-kinetic 연구를 수행하였다. 아울러 실험 중에 액체 질소로 급냉하여 얻은 시료를 대상으로 등온 및 비등온의 열분석 실험을 수행하고 JMA식과 Hoffman-Lauritzentlr 을 사용하여 분석한 다음, 그 결과를 rheo-kinetic 해석결과와 비교함으로써 결정화 거동에 미치는 전단응력의 영향을 규명하였다. 일정전단속동하에서 수행한 rheo-kinetic 실험결과, 시간에 따른 저난응력의 증가와 용융열이 증가하는 경향이 매우 유사한 거동을 보이므로 전 단응력의 증가는 결정화가 일어남에 기인한 결과임을 확인할수 있었으며 고분자수지가 전단 이력을 받게 되면 분자배향의 결과로 결정화 유도시간이 짧아지고 결정화속도가 증가할 뿐 만 아니라 보다 더 높은 온도에서 결정화가 일어나게 됨을 알수 있었다. 또 결정화 반가기 시간과 Hoffman-Lauritzen 식의 매개변수들이 전단속도, 전단부가시간, 결정화 온도 등의 이력에 무관하게 전단응력에 따라 선형적으로 변하고 있으므로 전단유도 결정화거동은 수지 에 부가되는 전단응력에 직접적인 영향을 받음을 알수 있었다. 이상과같은 전단유도 결정화 거동에 관한 결과를 가공공정상의 열전달 현상과 결합하여 해서하면 성형품 내부의모폴로지 의 예측이 가능하므로 성형품 물성의 극대화 방안의 수립에 이용될수 있을것으로 사료된다.

• Polymer(Korea)
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• v.26 no.4
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• pp.501-507
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• 2002

In this work, diglycidylether of bisphenol-S (DGEBS) epoxy resin was prepared by alkaline condensation of bisphenol-S (BPS) with epichlorohydrin (ECH) in the presence of NaOH catalyst. The structure of the synthesized DGEBS epoxy resin was confirmed by IR, NMR spectra, and elemental analysis. The curing reaction and glass transition temperature ($T_g$) of DGEBS epoxy resin cured with phthalic anhydride (PA) and tetrahydrophthalic anhydride (THPA) at curing agents were studied by dynamic differential scanning calorimetry (DSC). The thermal stability of the cured specimen was investigated by thermogravimetric analysis (TGA). As a result, the activation energy ($E_a$) of DGEBS/PA system was higher than that of DGEBS/THPA system, whereas $T_g$, initial decomposed temperature (IDT), and decomposition activation energy ($E_t$) of DGEBS/PA were lower than those of DGEBS/THPA. This was probably due to the fact that the crosslinking density of DGEBS/THPA was increased by ring strain of curing agent.

• Elastomers and Composites
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• v.45 no.1
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• pp.12-16
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• 2010

In this work, the effect of hydrophobic treated silica on the water absorption, thermal stabilities, and mechanical properties of the epoxy nanocomposites were investigated as a function of the silica content. As filler, fumed silica treated by dimethyldichlorosilane was used. It was found that the silica was well dispersed in the epoxy resins by the melt-mixing method with the addition of a silane coupling agent. The water absorption of the nanocomposites decreased with an increase of the silica content due to the effect of hydrophobic treated silica. The thermal properties, such as thermal degradation temperature, glass transition temperature ($T_g$), and coefficient of thermal expansion (CTE), of the nanocomposites were improved by the addition of silica. Furthermore, the mechanical properties of the nanocomposites, that is, the tensile strength and modulus, were enhanced with increasing silica content. This was attributed to the physically strong interaction between silica and epoxy resins.

• 한국해양학회지
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• v.7 no.1
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• pp.19-23
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• 1972

Based on the data collected during January of 1963, 1964 and 1965, heat transfer from the sea to the air over the south-western part of the Japan Sea was evaluated by the formula of Jacobs. The mean sensible heat transfer and the rate of evaporation in the mild winter of 1964 were 360ly day$\^$-1/ and 8.1mm day$\^$-1/, respectively. However, these values increased as much as 690ly day$\^$-1/ and 14.4mm day$\^$-1/ in the severe winter of 1963. The heat hudget of the Japan Sea in January were related to the magnitude of cold water mass formed in August in the Korea Strait.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.288-291
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• 2005

Resol type phenol-formaldehyde (PF) resin was synthesized by addition reaction of formaldehyde (F) and phenol (P). And the PF resin was synthesized by condensation reaction in which water was removed. In this work, we studied the influence of experimental parameters in the addition reaction, such as F/P mole ratio, amount of catalyst, reaction temperature, reaction time, and so on. Also, we studied the influence of molecular weight and viscosity of PE resin as a function of condensation time. As a result, in addition reaction, the reaction time decreased remarkably as the catalyst concentration increased, and the time decreased with increasing reaction temperature at a constant catalyst concentration. Also, in condensation reaction, the viscosity of resol type PF resin increased from 1500 to 9000 cps as a function of condensation time; molecular weight showed from 500 to 1100 g/mol.