• Fibers and Polymers
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• 제5권4호
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• pp.259-263
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• 2004

Rubber-modified epoxy resins have been employed as adhesive and matrix materials for glass and corbon-fiber composites. The behavior of fracture around a crack tip for rubber-modified epoxy resin is investigated through the acoustic emission (AE) analysis of compact tension specimens. Damage zone and rubber particles distributed around a crack tip were observed by a polarized optical microscope and an atomic force microscope (AFM). The damage zone in front of pre-crack tip in rubber-modified specimen $(15wt\%\; rubber)$ began to form at about $13\%$ level of the fracture load and grew in size until $57\%$ load level. After that, the crack propagated in a stick-slip manner. Based on time-frequency analysis of AE signals and microscopic observation of damage zone, it was thought that AE signals with frequency bands of 0.15-0.20 MHz and 0.20­0.30 MHz were generated from cavitation in the damage zone and crack propagation, respectively.

• Carbon letters
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• 제10권4호
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• pp.314-319
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• 2009

The surface treatment effects of reinforcement filler were investigated based on the dynamic mechanical properties of mutiwalled carbon nanotubes (MWCNTs)/epoxy composites. The as-received MWCNTs(R-MWCNTs) were chemically modified by direct oxyfluorination method to improve the dispersibility and adhesiveness with epoxy resins in composite system. In order to investigate the induced functional groups on MWCNTs during oxyfluorination, X-ray photoelectron spectroscopy was used. The thermo-mechanical property of MWCNTs/epoxy composite was also measured based on effects of oxyfluorination treatment of MWCNTs. The storage modulus of MWCNTs/epoxy composite was enhanced about 1.27 times through oxyfluorination of MWCNTs fillers at $25^{\circ}C$. The storage modulus of oxyfluorinated MWCNTs (OF73-MWCNTs) reinforced epoxy composite was much higher than that of R-MWCNTs/epoxy composite. It revealed that oxygen content led to the efficient carbon-fluorine covalent bonding during oxyfluorination. These functional groups on surface modified MWCNTs induced by oxyfluorination strikingly made an important role for the reinforced epoxy composite.

• Elastomers and Composites
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• 제43권1호
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• pp.39-48
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• 2008

상용 에폭시 수지의 접착력은 XNBR을 첨가함으로써 달성할 수 있으나 이는 필연적으로 유리전이온도(Tg)의 감소를 수반하여 접착제의 내열성을 저하시킨다. 1,3-bis(3-aminopropyl) tetramethyldisiloxane과 hydroxy phthalic anhydride를 반응시켜 siloxane-imide를 합성하고, 이를 상용 에폭시 수지와 공중합시켜 변성 에폭시 수지를 합성하였다. 변성 에폭시 수지의 siloxaneimide 함량을 결정하기 위하여 접착력 및 유리전이온도를 2관능성 에폭시 수지의 경우와 비교하여 조성비를 정하였다. Siloxane-imide와 공중합된 30% 변성 에폭시 수지는 5% XNBR을 첨가한 경우 0.42 N/mm의 박리 강도와 $155^{\circ}C$의 유리전이온도를 나타내어 die-bond용 접착제에 요구되는 물성 값인 0.3 N/mm 이상의 박리 강도와 $150^{\circ}C$ 이상의 유리전이온도를 충분히 만족 시킴을 알 수 있었다. 변성 에폭시 수지의 내 산성, 내 알칼리성 및 내습성을 평가한 결과 벤젠 링과 이미드 링의 영향으로 산, 염기 조건에서는 상용 에폭시 수지 대비 무게 변화폭이 감소하였지만 수분 조건에서는 무게 변화폭이 증가한 것을 알 수 있었다. 5% XNBR을 첨가한 30% 변성 에폭시 수지의 경우, 인장응력과 신장률이 상용 에폭시 수지 대비 약 220% 향상되었는데 이는 siloxane의 유연한 성질 때문인 것으로 판단된다.

• 전기학회논문지
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• 제65권9호
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• pp.1511-1517
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• 2016

The aim of this study is to improve of properties for electrical AC insulation breakdown strength using epoxy/micro-nano alumina composites with adding glycerol diglycidyl ether (GDE:1,3,5g). This paper deals with the effects of GDE addition for epoxy/micro alumina contents (40,50,60wt%)+surface modified nano alumina(1_phr) composites. 14 kinds specimen were prepared with containing epoxy resins, epoxy micro composites and epoxy nano-micro alumina mixture composites. Average particle size of nano and micro alumina used were 30nm and $1{\sim}2{\mu}m$, respectively. The micro alumina used were alpha phase with Heterogeneous and nano alumina were gamma phase particles of spherical shape. The electrical AC insulation breakdown strength was evaluated by sphere to sphere electrode system and raising velocity 1kV/s. The AC breakdown strength decreased insulation properties of multi-composites according to increasing micro alumina and GDE addition contents.

• 한국정밀공학회지
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• 제27권12호
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• pp.113-118
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• 2010

For a present study, woven type carbon fibers were surface-modified by oxygen plasma to improve adhesive strength between carbon fibers and epoxy. The change of hydrophilic properties by the plasma modification was investigated through the contact angle measurement and the calculation of surface energy of carbon fiber due to the oxygen plasma modification. FESEM and XPS analyses were performed to study the chemical and physical changes on the surface of carbon fibers due to the oxygen plasma modification. Pin-on-disk wear tests were conducted under dry condition using unmodified and plasma-modified carbon/epoxy composites to investigate the effect of plasma modification on the wear behavior of woven type carbon/epoxy composites. The results showed that the friction coefficient and the wear rate of plasma-modified carbon/epoxy composites were lower than those of unmodified carbon/epoxy composites, respectively. XPS analysis showed that new functional group of a carbonyl type was created on the carbon fibers by the $O_2$ plasma treatment, which enhanced adhesive strength between carbon fibers and epoxy, leading to improve wear properties

• Elastomers and Composites
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• 제50권3호
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• pp.167-174
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• 2015

Anionic epoxy compound was synthesized and added to asphalt aiming to prepare self-healing asphalt. Epoxy-modified asphalt showed excellent modification effect and healing effect as well. The results revealed that with 5% addition of polymer the tensile strength, impact strength and complex shear modulus of the polymer-modified asphalt increased by 65%. 64% and 35%, respectively. It seems that high interaction occurs between polymer and asphalt matrix. Self-healing efficiency of the polymer-modified asphalt based on tensile strength showed 100%, comparing to 79% of straight asphalt. In impact experiment the polymer-modified asphalt showed 99% of healing efficiency, comparing to 77% of straight asphalt. In rheological experiment the polymer-modified asphalt showed 103% of healing efficiency, comparing to 72% of straight asphalt. It appears that the ionic bonding existing in epoxy polymers contributed to high values of self-healing efficiency. The polymer which has high intermolecular force fills the crack of the asphalt, pulling the opponent side each other, and so the original properties were restored.

• Carbon letters
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• 제12권3호
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• pp.177-179
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• 2011

The use of carbon nanotubes (CNTs) as a reinforcing material in a polymer matrix has increased in various industries. In this study, the flexural behavior of CNT-modified epoxy/basalt (CNT/epoxy/basalt) composites is investigated. The effects of CNT modification with silane on the flexural properties of CNT/epoxy/basalt composites were also examined. Flexural tests were performed using epoxy/basalt, oxidized CNT/epoxy/basalt, and silanized CNT/epoxy/basalt multi-scale composites. After the flexural tests, the fracture surfaces of the specimens were examined via scanning electron microscopy (SEM) to investigate the fracture mechanisms of the CNT/epoxy/basalt multi-scale composites with respect to the CNT modification process. The flexural properties of the epoxy/basalt composites were improved by the addition of CNTs. The flexural modulus and strength of the silane-treated CNT/epoxy/basalt multi-scale composites increased by approximately 54% and 34%, respectively, compared to those of epoxy/basalt composites. A SEM examination of the fracture surfaces revealed that the improvement in the flexural properties of the silane-treated CNT/epoxy/basalt multi-scale composites could be attributed to the improved dispersion of the CNTs in the epoxy.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.176-177
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• 2014

Although the modified epoxy mortar can be applied to the reinforcement for RC member, the mortar has been little used in construction site. In addition, there is a few studies regarding the experiment as the material improving the seismic performance. Therefore, this study is to propose an effective reinforcement alternative for RC Ordinary Moment Resisting Frame (OMRF) through evaluation of seismic performance and economic analysis. The findings of this study can be utilized as the basic data in construction sites when the modified epoxy mortar is applied for seismic performance reinforcement.

• 접착 및 계면
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• 제22권1호
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• pp.8-15
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• 2021

본 연구에서는 우레탄 변성 에폭시의 유연성 부여를 위해 propylene glycol(PPG) 기반 diamine인 Jeffamine D-400을 이용하여 폴리올을 만들고 이를 이용하여 우레탄 변성 에폭시를 합성하였다. Bisphenol A diglycidyl ether(BADGE)에 합성한 우레탄 변성 에폭시와 경화제, 경화촉진제를 배합하여 에폭시 접착제를 제조하고 접착강도 측정으로 전단 강도를 측정하였다. 측정 결과 합성한 우레탄 변성 에폭시의 우레탄 결합과 PPG사슬 도입을 통한 유연성 부여 효과로 인해 전단 강도와 전단 신율이 증가하는 경향을 보였다. 이러한 결과는 높은 가교 밀도로 인해 사용에 제약을 받고 있는 구조용 접착제에 적용이 가능할 것으로 판단된다.

• 접착 및 계면
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• 제25권1호
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• pp.162-168
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• 2024

The effect of maleinized polybutadiene (MPB) on the mechanical properties of epoxy resins including adhesion strength, elongation and impact peel resistance was investigated in this study, in which MPB is an anhydride-functionalized polybutadiene prepolymer. Different molecular weights (3.1K and 5.6K) of MPB were added to diglycidyl ether bisphenol-A (DEGBA), an epoxy resin, to increase its impact peel strength and elongation. At various loading percent (5, 10, 15, 20 and 25 wt%) of MPB in the epoxy resin, significant improvements of mechanical properties were observed. According to the comparative analysis results, the modified epoxy system with 15 wt% (3.1K) MPB exhibited the highest lap shear strength, about 40% higher than that of neat epoxy. The tensile strength and elongation steadily and simultaneously increased as the loading percent of MPB increased. The impact peel strengths at low (-40℃) and room (23℃) temperatures were substantially improved by MPB incorporation into epoxy resins. Reactive and flexible MPB prepolymer seems to construct strong nano-structured networks with rigid epoxy backbones without sacrificing the tensile and adhesion strengths while increasing impact resistance/toughness and elongation properties. For higher impact peel while maintaining adhesion and tensile strengths, approximately 10-15 wt% MPB loading in epoxy resin was suggested. Consequently, incorporation of functionalized MPB prepolymer into epoxy system is an easy and efficient way for improving some crucial mechanical properties of epoxy resins.