• Title/Summary/Keyword: initial curing time

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TEMPERATURE CHANGES IN THE PULP ACCORDING TO VARIOUS ESTHETIC RESTORATIVE MATERIALS AND BASES DURING CURING PROCEDURE (광중합 시 수종의 심미적 수복재와 이장재의 사용에 따른 치수내 온도변화)

  • 장혜란;이형일;이광원;이세준
    • Restorative Dentistry and Endodontics
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    • v.26 no.5
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    • pp.393-398
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    • 2001
  • Polymerization of light-activated restorations results in temperature increase caused by both the exothermic reaction process and the energy absorbed during irradiation. Within composite resin, temperature increases up to 2$0^{\circ}C$ or more during polymerization. But, insulation of hard tissue of tooth lowers this temperature increase in pulp. However, many clinicians are concerned about intrapulpal temperature injury. The purpose of this study was to evaluate temperature changes in the pulp according to various restorative materials and bases during curing procedure. Caries and restoration-free mandibular molars extracted within three months were prepared Class I cavity of 3$\times$6mm with high speed handpiece fissure bur. 1mm depth of dentin was evaluated with micrometer in mesial and distal pulp horns. Pulp chambers were filled with 37.0$\pm$0.1$^{\circ}C$ water to CEJ. Chromium-alumina thermocouple was placed in pulp horn below restorative materials for evaluating of temperature changes. This thermocouple was connected to temperature-recording device(Multiplication analyzer MX, 6.000, JAPAN). Temperature changes was evaluated from initial 37.$0^{\circ}C$ after temperature changes to 37.$0^{\circ}C$. Tip of curing unit was placed in the center of prepared cavity separated 1mm from restorative materials. Curing time was 40s. The restorative materials were used with Z 100, Fuji II LC, Compoglass flow and bases were used with Vitrebond, Dycal. Resrorative materials were placed in 2mm. The depth of bases were formed in 1mm and in this upper portion, resin of 2mm depth was placed. This procedure was performed 10 times. The results were as follows. 1. All the groups showed that the temperature in pulp increased as curing time increased 2. The temperature increase of glass ionomer was significantly higher than that of Resin and Compomer during curing procedure (P<0.05). 3. The temperature increase in glass ionomer base was significantly higher than that of Calcium hydroxide base during Resin curing procedure (P<0.05).

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Effects of 4BS Crystal Size on the Positive Plate Behavior in Lead Acid Battery (4BS 결정크기에 따른 납축전지 양극판 특성에 미치는 영향)

  • Jeong, Soon-Wook;Ku, Bon-Keun
    • Journal of the Korean Applied Science and Technology
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    • v.26 no.3
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    • pp.335-340
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    • 2009
  • This study investigates the paste mixing of positive active materials which, affect the life cycle of batteries in Pb-Ca-Sn grids, and generation of 4BS in a curing process and considers the effects of these things on the initial charge characteristics and life cycle. In the results of the experiments applied in this study, it was possible to reduce the curing time in which the fine 4BS was formed by the mixing of the positive active materials of lead acid battery applied at high temperature compared to that of the existing coarse 4BS and that represented some improvements in the life cycle performance.

Strength Characteristics of Concrete Subjected In Horizontal Continuous Vibration During Initial Curing (초기양생중에 수평연속진동을 받은 콘크리트의 강도특성)

  • 장희석;김명식;김종수;한중기
    • Journal of the Korea Concrete Institute
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    • v.13 no.5
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    • pp.423-429
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    • 2001
  • In this study, strength characteristics of concrete specimens subjected to horizontal continuous vibration during initial curing were investigated. As experimental variables, vibration velocity(0.25, 0.5, 1.0, 2.0, 4.0 kine) and vibration time(3, 6, 12, 24 hrs) were used. Density and segregation of the specimens were also investigated. Vibrating was started soon after placing, and strengths investigated consist of compressive strength, splitting tensile strength, and bond strength. Strengths decrease were hardly occurred at 0.25 kine vibration velocity regardless of vibration times and all strengths were increased for 3 hrs vibration at 0.5 kine vibration velocity. Density was increased for all specimens due to the vibration and there was no serious segregation under even 4 kine vibration velocity.

Study on engineering properties of xanthan gum reinforced kaolinite

  • Zhanbo Cheng;Xueyu Geng
    • Computers and Concrete
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    • v.31 no.6
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    • pp.501-511
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    • 2023
  • The strengthening efficiency of biopolymer treated soil depends on biopolymer type, concentration ratio, soil type, initial water content, curing time and mixing method. In this study, the physical and mechanical properties of xanthan gum (XG) treated kaolinite were investigated through compaction test, Atterberg limit test, triaxial test and unconfined compression test. The results indicated that the optimum water content (OWC) increased from 30.3% of untreated clay to 33.5% of 5% XG treated clay, while the maximum dry density has a slight increase from 13.96 kg/m3 to 14 kg/m3 of 0.2% XG treated clay and decrease to 2.7 kg/m3 of 5% XG treated clay. Meanwhile, the plastic limit of XG treated clay increased with the increase of XG concentration, while 0.5% XG treated clay can be observed the maximum liquid limit with 79.5%. Moreover, there are the ideal water content about 1.3-1.5 times of the optimum water content achieving the maximum dry density and curing time to obtain the maximum compressive strength for different XG contents, which the UCS is 1.52 and 2.07 times of the maximum UCS of untreated soil for 0.5% and 1% XG treated clay, respectively. In addition, hot-dry mixing can achieve highest UCS than other mixing methods (e.g., dry mixing, wet mixing and hot-wet mixing).

Strength Properties of Concrete According to Types of High Early Strength Cement and Curing Method (조강형 시멘트의 종류 및 양생방법에 따른 콘크리트의 강도특성)

  • Chang, Chun-Ho;Lee, Wang-Sup;Jung, Yong-Wook;Chung, Youn-In
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.1
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    • pp.76-84
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    • 2017
  • This study selected a method which uses high early strength cement as a way to reduce the curing time and curing energy source of concrete secondary products and reviewed the improvement in the initial strength of concrete secondary products setting the target strength of the concrete capable of removing the form to 15MPa and the curing time to 6 hours. As a result of the test, the only specimen which achieved the form removal strength of 15 MPa only through atmospheric curing within the target curing time of 6hours was ACC-100, and the specimens of TRC-100 and TRC-50 satisfied the values of 6 hours and 15MPa through steam curing. However, we could see that it was difficult to secure workability in the case of the specimen of ACC-100 due to its high rapid setting property and a retarder such as anhydrous citric acid was required to be used to improve the workability. When we look into the pattern following changes in the water to binder ratio, while, in the case of stream curing, OPC-100, TRC-100, and TRC-50 were all found to satisfy achievement of the form removal strength within 6hours as the water to binder ratio decreased, in the case of atmospheric curing, TRC-100, and TRC-50 achieved 15MPa within 12hours.

Improvement of Pot Life in the Epoxy Resin-based Adhesive Formulation by Size Control and Coating of Curing Accelerator Powders (경화촉매 분말의 입도조절 및 표면코팅에 의한 에폭시 레진 기반 혼합조성의 상온 보관특성 개선)

  • Lee, Jun-Sik;Hyun, Chang-Yong;Lee, Jong-Hyun
    • Journal of Powder Materials
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    • v.15 no.2
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    • pp.119-124
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    • 2008
  • To increase pot life in the formulation mixed with bisphenol F epoxy resin, anhydride-based curing agent, and imidazole-based curing accelerator powders as a paste material for high-speed RFID chip bonding, size variation of the imidazole-based powders and a coating method of the powders were adopted in this study. In experiment with regard to the size variation, the pot life was not outstandingly increased. Through the idea using the coating method, however, the pot life was increased up to 4.25 times in comparison with the addition of initial imidazole-based powders. Consequently, successive bonding of RFID chip could be performed with very short time of 5sec using the suggested formulation having improved pot life.

Role of F/P Ratio on Curing Behavior for Phenolic Resol and Novolac Resins by FT-IR (FT-IR 분석에 의한 레졸과 노블락 페놀 수지의 경화거동에 미치는 F/P 몰비)

  • Lee, Young-Kyu;Kim, Hyun-Joong
    • Journal of Adhesion and Interface
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    • v.2 no.3
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    • pp.16-24
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    • 2001
  • The curing behavior of a phenolic resin (F/p: 1.3, 1.9, 2.5 for resol resin, F/P: 0.5, 0.7, 0.9 for novolac resin) has been studied by FT-IR spectroscopy. In this study is to synthesis of resol and novolac type phenolic resin with different F/P molar ratios and to compare the level of cure at different curing temperature conditions ($130^{\circ}C$, $160^{\circ}C$, $180^{\circ}C$ for resol resin, $160^{\circ}C$, $170^{\circ}C$, $180^{\circ}C$ for novolac resin) for 3, 5, 7, 10, 20, and 60 (min.), respectively. The conversion (${\alpha}$) was determined by the ratio of the peak area with time to the peak area of non-baked phenolic QH ($3300cm^{-1}$) at spectra. It is concluded that the initial curing rate of resol and novolac resin was increased as the molar ratio of formaldehyde/phenol increased and as the curing temperature of resin increased. According to the analysis was by the homogenous first-order model, the initial curing rate of resol and novolac resin was increased as the molar ratio of formaIdehyde/phenol increased at specific curing temperature.

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Measurement of the Early-Age Coefficient of Thermal Expansion and Drying Shrinkage of Concrete Pavement (콘크리트포장의 초기 열팽창계수 및 건조수축 측정 연구)

  • Yoon, Young-Mi;Suh, Young-Chan;Kim, Hyung-Bae
    • International Journal of Highway Engineering
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    • v.10 no.1
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    • pp.117-122
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    • 2008
  • Quality control of the concrete pavement in the early stage of curing is very important because it has a conclusive effect on its life span. Therefore, examining and analyzing the initial behavior of concrete pavement must precede an alternative to control its initial behavior. There are largely two influential factors for the initial behavior of concrete pavement. One is the drying shrinkage, and the other is the heat generated by hydration and thermal change inside the pavement depending on the change in the atmospheric temperature. Thus, the coefficient of thermal expansion and drying shrinkage can be regarded as very important influential factors for the initial behavior of the concrete. It has been a general practice up until now to measure the coefficient of thermal expansion from completely cured concrete. This practice has an inherent limitation in that it does not give us the coefficient of thermal expansion at the initial stage of curing. Additionally, it has been difficult to obtain the measurement of drying shrinkage due to the time constraint. This research examined and analyzed the early drying shrinkage of the concrete and measurements of the thermal expansion coefficients to formulate a plan to control its initial behavior. Additionally, data values for the variables of influence were collected to develop a prediction model for the initial behavior of the concrete pavement and the verification of the proposed model. In this research, thermal expansion coefficients of the concrete in the initial stage of curing ranged between $8.9{\sim}10.8{\times}10^{-6}/^{\circ}C$ Furthermore, the effects of the size and depth of the concrete on the drying shrinkage were analyzed and confirmed.

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Micro Bonding Using Hot Melt Adhesives

  • Bohm, Stefan;Hemken, Gregor;Stammen, Elisabeth;Dilger, Klaus
    • Journal of Adhesion and Interface
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    • v.7 no.4
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    • pp.28-31
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    • 2006
  • Due to the miniaturization of MEMS and microelectronics the joining techniques also have to be adjusted. The dosing technology with viscous adhesives does not permit reproducible adhesive volumes, which are clearly under a nano-liter. A nano-liter means however a diameter of bonding area within the range of several 100 micrometers. Additional, viscous adhesives need a certain time, until they are cross linked or cured. The problem especially in the MEMS is the initial strength, since it gives the time, which is needed for joining an individual adhesive joint. The time up to the initial strength is with viscous, also with fast curing systems, within the range of seconds until minutes. Until the reach of the initial strength, the micro part must be fixed/held. Without sufficient adjustment/clamping it can come to a shift of the micro parts. Also existing micro adhesive bonding processes are not batch able, i.e. the individual adhesive joints of a micro system must be processed successively. In the context of the WCARP III 2006 now an innovative method is to be presented, how it is possible to solve the existing problems with micro bonding. i.e. a method is presented, which is batch able, possess a minimum joining geometry with some micrometers and is so fast that no problems with the initial strength arise. It is a method, which could revolutionize the sticking technology in the micro system engineering.

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Strength Development Characteristics of Clay Stabilized with Electric Furnace Steel Slag (전기로 제강슬래그로 안정화된 연약점토의 강도 발현 특성)

  • Hyeongjoo Kim;Taegew Ham;Taewoong Park;Taeeon Kim
    • Journal of the Korean GEO-environmental Society
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    • v.25 no.5
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    • pp.29-37
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    • 2024
  • This study aimed to investigate the changes in chemical components that occur when weak clay is mixed with steel slag modified with calcium oxide, and to understand the expression characteristics of compressive strength according to hydrophilicity and curing time. XRF testing, SEM imaging, vane shear strength and uniaxial compressive strength testing were conducted. Calcium (Ca) released from the steel slag increases the Ca content in clay by increasing the number of crystal particles and forming a coating layer known as calcium silicate hydrate (CaO-SiO2-H2O) through chemical reactions with SiO2 and Al2O3 components. The weak clay stabilized with steel slag is classified into an initial inactive zone where strength relatively does not increase and an activation zone where strength increases over curing time. The vane shear strength of the initial inactive area was found to be 4.4 to 18.4 kN/m2 in the state of the weight mixing ratio Rss 30% (steel slag 30% + clay 70%). In the case of the active area, the maximum uniaxial compressive strength increased to 431.8 kN/m2 after 480 hours of curing time, which increased due to the apparent adhesion strength of clay through pozzolanic reaction. Therefore, considering the strength expression characteristics of stabilized mixed clay based on the mixing ratio (Rss) during the recycling of steel slag can enhance its practicality in civil engineering sites.