• Title/Summary/Keyword: 상온 경화

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Evaluation of Adhesion Property with Pot Life and Curing Humidity of GFRC and Epoxy Adhesive (유리섬유강화 복합재료와 에폭시 접착제의 가사시간과 경화습도에 따른 접착 강도 평가)

  • Yoo, Ji-Hoon;Shin, Pyeong-Su;Kim, Jong-Hyun;Lee, Sang-Il;Park, Joung-Man
    • Journal of Adhesion and Interface
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    • v.21 no.2
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    • pp.65-70
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    • 2020
  • Epoxy adhesive was mainly used to combine different composite materials. Epoxy adhesive was a typical thermosetting resin that can be bonded by changing from a linear structure to a three-dimensional network structure by curing reaction of epoxy and hardener. The curing conditions of epoxy adhesive were different with different types of hardener such as mixing ratio, curing time, and temperature. These curing conditions affected to the adhesive property of epoxy adhesive. In industry, it was difficult to proceed the applying epoxy adhesive and combining two parts immediately. The adhesive property decreased by humidity and pre-curing of epoxy adhesive in waiting time between two processes. In this paper, the glass fiber reinforced composite (GFRC) was combined with epoxy adhesive and adhesion property between epoxy adhesive and GFRCs was evaluated using single lap shear test. The different waiting times and humidity conditions were applied to epoxy adhesive in room temperature and adhesive property decreased as the waiting time increased. In small amount of humidity, the adhesive property increased because a small amount of moisture in the surroundings accelerated the curing reaction. In certain amount of humidity, however, the adhesion property decreased.

Fundamental Study on the Strength Development of Cement Paste using Hardening Accelerator and High-Early-Strength Cement (경화촉진제와 조강시멘트를 사용한 시멘트 페이스트의 강도발현에 대한 기초적 연구)

  • Min, Tae-Beom;Cho, In-Sung;Lee, Han-Seung
    • Journal of the Korea Institute of Building Construction
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    • v.13 no.4
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    • pp.407-415
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    • 2013
  • The purpose of this research is to verify the performance of hardening accelerator in cement paste through mechanical performance evaluation and micro structure analysis on hardening accelerator for development of super high early strength concrete. The research results showed that hardening accelerator produced $Ca(OH)_2$ when hydrated with cement, enhancing the degree of saturation of Ca ion by using differential thermal analysis. Moreover, porosity was reduced rapidly as capillary pores were filled by hydration products of $C_3S$. According to the experiment using hydration measurement testing, when 1% and 3% of accelerator were mixed, hydration rate increased toward the second peak point compared to high early strength cement, before the first peak point disappeared. It turned out that adding accelerator accelerated the hydration rate of cement, especially $C_3S$. The shape of C-S-H is shown depending on the amounts of accelerator added and the production and age of $Ca(OH)_2$ by using SEM to observes hydration products. Therefore, it's evident that hardening accelerator used in this research increases amounts of $Ca(OH)_2$ and accelerates $C_3S$, it is effective for the strength development on early age.

Quality Changes of Dried Persimmons Depending on Pre-Treatment and Packaging Materials during Storage (전처리와 포장재에 따른 곶감의 저장 중 품질변화)

  • Kim Sang-Hee;Park Hyung-Woo;Lee Seon-Ah;Kim Yoon-Ho;Cha Hwan-Soo
    • Food Science and Preservation
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    • v.11 no.4
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    • pp.437-440
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    • 2004
  • To investigate the effects of pre-treatment and packaging materials for dried persimmon during 6 month storage, the citric acid, salt, xylitol, L-cystein was pre-treated on dried persimmon, and then packed with LDPE film($0.06\;{\mu}m$) and N/LDPE($0.06\;{\mu}m$). The rate of moisture contents, browning, fungi and weight loss of dried persimmon pre-treated with citric acid, salt, xylitol, L-cystein were changed a little in N/LDPE, but were highly changed in LDPE. The commodity of dried persimmon packed with N/LDPE was also higher than that of LDPE.

The Study on Phase Separation Development by Curing Reaction Rate for Unsaturated Polyester/Polyvinylacetate Semi-IPN (Unsaturated Polyester/Polyvinylacetate Semi-IPN의 경화반응속도에 따른 상분리현상 연구)

  • Chang, Won-Young;Kim, Moo-Sool;Kim, Jin-Hwan;Nam, Jae-Do
    • Polymer(Korea)
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    • v.25 no.1
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    • pp.78-89
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    • 2001
  • Morphological changes of unsaturated polyester/polyvinylacetate semi-IPN were studied while the phase separation and the cure reaction occurred in a competing fashion. The light scattering and thermal analysis techniques were used to investigate the phase separation rates and mechanical properties resultantly induced by molecular diffusion of thermoplastic polymer during the curing process of thermosetting polymer. The reaction activation energy was calculated by using Flynn-Wall method and the semi-IPN structure exhibited various phase-separation morphological characteristics. When PVAc composition was 10 wt%, the phase separation was not observed during the curing reaction, but the phase separation occurred in a similar fashion to nucleation and growth(NG) mechanism at room temperature. On the other hand, when PVAc composition was over 11.65 wt%, the phase separation was generated in the middle of the curing process. Consequently, the phase separation seemed to influence the curing reaction rate, which was also supported by the changing activation energy with conversion and PVAc composition. Finally, the total scattered intensity was measured at various temperature, and subsequently the diffusion rates of phase separation R(${\beta}m$) were evaluated.

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Effect of Loading Rate on the Deformation Behavior of SA508 Gr.1a Low Alloy Steel and TP316 Stainless Steel Pipe Materials at RT and 316℃ (상온과 316℃에서 SA508 Gr.1a 저합금강 배관과 TP316 스테인리스강 배관의 변형거동에 미치는 하중속도의 영향)

  • Kim, Jin Weon;Choi, Myung Rak
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.4
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    • pp.383-390
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    • 2015
  • This study conducted tensile tests on SA508 Gr.1a low alloy steel and SA312 TP316 stainless steel piping materials under various strain rates at room temperature (RT) and $316^{\circ}C$ to investigate the effects of loading rate on the deformation behavior of nuclear piping materials. At RT, the deformation behavior for both pipe materials showed a typical loading rate dependence, i.e., the strength increased and the ductility decreased as the loading rate increased. At $316^{\circ}C$, however, the strength and elongation of SA508 Gr.1a low alloy steel decreased as the loading rate increased, and its reduction of area non-linearly varied with the loading rate. For SA312 TP316 stainless steel, the strength, elongation, and reduction of area at $316^{\circ}C$ were almost the same regardless of the loading rate. At both temperatures, the strain hardening capacity was nearly independent of the loading rate for SA508 Gr.1a low alloy steel, while it decreased with increasing loading rate for SA312 TP316 stainless steel.

Self Cleaning and Durability of Silicate Impregnant of Concrete (콘크리트 침투성 표면보호재의 자기세정 및 내구특성)

  • Song, Hun;Chu, Yong-Sik;Lee, Jong-Kyu
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.433-436
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    • 2008
  • Deterioration in the concrete structure are due to carbonation, chloride ion attack and frost attack. Therefore, concrete structure is needed to surface protection for increase durability using silicate impregnants. Thus, this study is concerned with self-cleaning and durability of silicate hydrophilic impregnants of concrete structure using lithium and potassium silicates. From the experimental test results, lithium and potassium silicates have a good properties as a carbonation resistance. Lithium and potassium silicates make good use of hydrophilic impregnants of concrete structures.

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Physical Properties and Flame Retardancy of PU Coatings Polymerized with Two Different Types of Isocyanates and Dichloro-Polyester Polyol (두 종류의 이소시아네이트와 디클로로-폴리에스테르 폴리올로부터 중합한 PU 난연도료의 도막물성 및 난연성)

  • 양인모;김성래;박형진;함현식;우종표
    • Polymer(Korea)
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    • v.26 no.2
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    • pp.193-199
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    • 2002
  • The dichloro-polyester polyol (DCBAO) which was synthesized in our earlier work was cured at room temperature with two different type of curing agents including Desmodur N-3300 and Desmodur L-75 to get a polyurethane flame-retardant coatings (DCBAO/N-3300=DEBAN and DCBAO/L-75=DCBAL). We could not observe any deterioration of physical properties of the flame-retardant PU coatings (UCBAN and DCBAL) in comparison with the conventional PU coatings. Thermal resistance of DCBAL-type flame-retardant coatings, which was measured by yellowness index difference, was inferior to that of DCBAL-type PU coatings. We believe that this phenomena is attributed to the poor thermal resistance of Desmodur L-75 isocyanate. It was observed that the LOI values were 25∼26% for the PU coatings containing 20∼30 wt% of 2,4-dichlorobenzoic acid.

Performance of Fresh and Hardened Ultra High Performance Concrete without Heat Treatment (상온 양생한 초고성능 콘크리트(UHPC)의 경화 전과 후의 성능 관계)

  • Kang, Sung-Hoon;Hong, Sung-Gul
    • Journal of the Korea Concrete Institute
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    • v.26 no.1
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    • pp.23-34
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    • 2014
  • This study investigates the relationship between the performance of fresh and hardened Ultra-High Performance Concrete (UHPC) without heat treatment. The performance of fresh UHPC is determined by the slump flow test related to the fluidity of concrete mixtures, and the air content test. The variables of these tests are the water to binder ratio, superplasticizer dosages and volume fractions of steel fiber. Generally, insufficient fluidity and excessive air contents in concrete mixtures lead to the insufficient packing density related to the performance of harden concrete. The performance of hardened UHPC is determined by the compressive and flexural tensile tests. The results of the fresh UHPC tests show that there is the linear correlation between each variable and the slump flow diameter, and that the slump flow diameter is linearly decreased as the air content ratio increase. Using these results, the formula is developed to predict the fresh performance before mixing UHPC. The results of the hardened UHPC tests show that the hardened performance is not influenced by the air content ratio in the range of 3.2 to 4.2 per cent. However, the flexural tensile strength dominantly influenced by the volume fractions of steel fiber.

Mechanical Characteristics of Stainless Steel TP 304, TP 316 under Low Temperature Environment (저온 기계 재료용 TP 304, TP 316 소재의 저온거동 특성 평가)

  • Cho, Seung-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.10
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    • pp.125-130
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    • 2017
  • Automotive materials and plant modules need to be prepared for freezing parts to operate in extreme areas such as Eastern Europe, Russia, and Canada. However, the only thing that has been done for ultra-qualifying materials for extremely low operating materials is that only the effects at low temperatures are conducted at room temperature, and the effects at low temperatures are only identified at low speeds. Therefore, this study examined the low-temperature characteristics of materials by conducting comparative tests on the mechanical properties of the room at the temperature and temperature of TP304 and TP316 materials, which are the most common materials.

The Processing and Characterization of Sol-Gel Derived Ferroelectric PMN Powders and Thin Films (졸-겔법에 의한 강유전성 PMN 분말 및 박막의 제조와 특성)

  • Hwang, Jin-Myeong;Jang, Jun-Yeong;Eun, Hui-Tae
    • Korean Journal of Materials Research
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    • v.8 no.12
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    • pp.1138-1145
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    • 1998
  • The sliding wear behavior of Ni-base hardfacing alloy, Deloro 50, was investigated at the contact stresses of 15ksi and 30ksi under the various wear environments. In air at room temperature, Deloro 50 showed lower wear resistance than Stellite 6 even at 15ksi due to the occurrence of severe adhesive wear. This seems to be caused by the lower hardness and work- hardening rate of Deloro 50 than those of Stellite 6. In water at room temperature, Deloro 50 showed as good wear resistance as Stellite 6 at 15ksi. It was considered to be due to that water could effectively prevent metal to metal contact through contacting asperities. However, Deloro 50 showed severe adhesive wear at 30ksi in water at room temperature. It seems to be that the water could not suppress adhesion wear at 30ksi. At $300^{\circ}C$ in air, Deloro 50 exhibited higher wear resistance than Stellite 6 even at 30ksi. It was considered that the oxide glaze layers formed on wear surface during sliding, effectively prevented direct metal-to-metal contacts.

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