• Title/Summary/Keyword: high curing temperature

Search Result 504, Processing Time 0.026 seconds

Fabrication of polymer thick film resistor and study on resistance variation regarding curing temperature (폴리머 후막 저항체의 제작 및 경화 온도에 따른 저항 값 변화에 대한 연구)

  • Yoo, Myong-Jae;Lee, Sang-Myong;Park, Seong-Dae;Kang, Nam-Kee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2006.06a
    • /
    • pp.212-213
    • /
    • 2006
  • Polymer thick film resistor paste was fabricated using various materials. Inorganic materials of carbon black and graphite were selected as fillers and epoxy resin was selected as organic material. Solvent with high boiling temperature was applied to adjust viscosity. A designed test coupon pattern was used to evaluate fabricated resistors. Aspect ratio of 1 was selected for evaluating resistor values. Electrical properties of fabricated resistors were measured and their values analyzed in relation to paste composition. PTF fabricated using carbon black as fillers achieved resistor value of $530{\Omega}/sq$.

  • PDF

Dielectric Properties of Oriental Lacquer Coating Network

  • 홍진후;김현경;허귀석;최종오
    • Bulletin of the Korean Chemical Society
    • /
    • v.18 no.7
    • /
    • pp.715-719
    • /
    • 1997
  • In order to study the dielectric properties of the oriental lacquer films, three different films have been prepared differing purification and curing procedures. Dielectric properties were measured in the frequency range of 1 Hz to 105 Hz at various temperatures between - 50 ℃ and 150 ℃. The DEA using 1 Hz showed that glass transition and secondary relaxation temperatures of oriental lacquer film are very time dependent. In addition, the frequency-independent negative peak between 25 ℃ and 45 ℃ was observed, which could represent the formation of crosslink by laccase enzyme during heating. On the contrary, the high temperature cured film showed a hardly noticeable negative peak at the temperature range. The relationship between thermodynamic properties and chemical structures has been discussed based on the analysis of the dielectric relaxation behavior using the Cole-Cole plot and the dielectric relaxation intensity.

Analysis of Setting Delay Performance Change of Super Retarding Agent According to the Change of Mixing Rate at 20℃ (20℃ 조건에서 초지연제 혼입율 변화에 따른 응결지연 성능 변화 분석)

  • Lim, Gun-Su;Han, Soo-Hwan;Hyun, Seung-Yong;Kim, Jong;Han, Min-Choel;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • 2020.11a
    • /
    • pp.127-128
    • /
    • 2020
  • This research is part of the research for unifying the mass concrete and utilizing the rate of super retarding agent. We analyzed the performance of super retarding agent 20℃ conditions. It was found that there was no deterioration in fluidity and air quality due to the change in the super retarding agent mixing rate. It was found that when super retarding agent was mixed up to 0.5 %, it was delayed for 22.3 hours at 20℃. Therefore in order to ensure the performance required at the site, the super retarding agent mixing rate must be determined by fully considering the situation at the site. In addition it will be analyzed that super retarding agent performance analysis at high temperature will be required in subsequent studies.

  • PDF

Postharvest Handling and Marketing Management for Making High Salability of Sweetpotatoes (상품성 제고를 위한 고구마 수확 후 관리 및 출하기술)

  • Jeong, Byeong-Choon
    • Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
    • /
    • 2001.06a
    • /
    • pp.51-64
    • /
    • 2001
  • The qualities including taste of sweetpotato stored during the winter which can display in the spring market in Korea are affected by availability of storage for the roots. In order to make high storage availability of sweetpotato, the postharvest handlings should be done thoroughly from the moment of harvest until shipping them to the market. A lot of procedures that must be handled carefully for improving postharvest management are as follows; digging, trimming, gathering, putting in storage containers, carrying them from field to house, curing, storing, washing, drying, selecting marketable roots, packing and shipping to the market, etc.. Sweetpotatoes have a high moisture content, and a relatively thin and delicate skin, and are sensitive to chilling, so careless postharvest handling can lead to both quantitative and qualitative losses which may be extremely high in some circumstances. From now on research has concentrated on the improvement of postharvest conditions to increase yield and lower disease rates. Storage, which makes sweetpotatoes available through out the year, benefits both the producer and the consumer. Seven very important points must be needed in order to get the best quality marketable roots in the storing of sweetpotatos : $\circled1$The storage house must be clean and sanitary, $\circled2$The crop must be harvested before the first frost to avoid low-temperature injury, $\circled3$Particular care must be taken to avoid cutting, bruising, or other injuries of the sweetpotatoes during digging, picking up, grading, placing in containers, and moving to the storage house, $\circled4$Select sound, disease-free roots for storage $\circled5$Sweetpotatoes should be stored in properly stacked containers $\circled6$Cure immediately after harvest, preferably at 32∼33$^{\circ}C$ and 90 to 95 percent relative humidity for 4 to 7 days, After curing the temperature should be reduced to 13$^{\circ}C$ to 16$^{\circ}C$ by ventilating the storage with outside air. $\circled7$Store at 12$^{\circ}C$ to 14$^{\circ}C$ and a relative humidity of 80 to 85 percent. Storage houses should be located on suitable sites and should be tightly constructed and insulated so that temperature and humidity will be uniform. Sweetpotatoes are usually not washed and graded, and lately sometimes washed, graded, waxed, before being shipped to market. Consumer packaging of sweetpotatoes in paper boxes(10-15kg) or film bags is done mainly to aid marketing. The shelf life of washed roots in consumer packs in only 1 to 2 weeks. Weight loss of roots during marketing is much less in perforated film bags than in mesh and paper bags. Perforation of 0.8 to 1kg polyethylene bags with about six 6mm holes is essential ; to lower the internal relative humidity and avoid excessive sprouting, rooting, and dampness. Development and use of better postharvest handling with good storage facilities or marketing methods can minimize sweetpotate losses and has an effect of indirectly increasing productivity and farmer’s income.

An Experimental Study on Measure to Moisture Contents of Concrete (콘크리트 내부의 수분함유량 측정에 관한 실험적연구)

  • Park, Won-Sup;Kim, Heung-Youl;Kim, Hyung-Jun
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
    • /
    • 2008.11a
    • /
    • pp.428-433
    • /
    • 2008
  • The strength capacity properties of concrete are much influenced by water content which has a significant effect on concrete spalling, especially, in high temperature areas. Therefore, the properties of the material's shall be closely examined first by measuring the water content in each material in order to analyze Concrete Fire Characteristics, and a reliable measuring method shall be presented in order to derive the following influence. The method used to measure the water content within concrete is mainly divided into 4 types; ASTM method, Nuclear Magnetic method, Ultrasonic measurement method, Radio Wave method, etc. It is essential to use a reliable measuring method for each experiment. In this experiment, we measured the water content and humidity of concrete by two methods; Relative/Absolute humidity method using VISALA HM44 measuring equipment which is easily measurable compared with other methods regardless of the shape of the experimental model, and a water content measuring experiment using ASTM C 566. If the aggregates are under the condition that their surface is dry but in saturation, there is no change of water content according to concrete curing methods. However if the aggregates are absolutely dry, the water content is significantly changed according to concrete curing methods.

  • PDF

Plastic and Drying Shrinkage Cracking Reduction by the Bubble Sheet Curing (버블시트 피복양생법에 의한 소성 및 건조수축 균열저감)

  • Lee, Joung-Gyo;Han, Cheon-Goo
    • Journal of the Korea Institute of Building Construction
    • /
    • v.16 no.3
    • /
    • pp.211-217
    • /
    • 2016
  • In this research, the performance of surface covering technique using a white-colored bubble sheet on reducing the cracking due to the plastic, and drying shrinkages for high rise building construction were evaluated by comparing the exposed surface without any surface treatment. From the results of the experiment conducted during fall season, desired results of decreased numbers, length, maximum width, and area of cracking were obtained without a significant difference on heat of hydration and cumulative temperature. Therefore, it is considered that the surface covering technique using bubble sheet is an appropriate method for preventing plastic and drying shrinkage cracking at fall season concrete construction.

Numerical Study for Tunnel Shotcrete Lining Operated Stress Measurement Techique Development During a Construction (시공중 터널 숏크리트 라이닝 작용응력 측정기법 개발을 위한 수치해석적 연구)

  • Shin, Hyu-Seong;Kim, Dong-Gyou;Jung, Yong-Su;Hwang, Jae-Hong;Bae, Gyu-Jin
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2008.03a
    • /
    • pp.754-761
    • /
    • 2008
  • In general, stress measurement of existent shotcrete lining be used by pressure cells. but, measuring instrument is lost by high pressure at shotcrete lining construction and pressure cell's measurement value have to low believability by natural conditions like curing temperature. In this study, proposed techniques to measure without utilizing sensitive stress sensor in natural condition at point that want stress of shotcrete lining after shotcrete lining construction. Executed numerical analysis to forecast stress level that interact in tunnel shotcrete lining, measured strain of hole by load action through hole in shotcrete lining. 3D FEM(finite element method) is enforced through various parameters curing time of shotcrete lining, thickness, load condition. Different model cases applied by parametic study. As analysis result, it could grasp development possibility of method that propose this time because it could examine corelation with strain by near hole of shotcrete lining and stress about load condition.

  • PDF

Prediction of expansion of electric arc furnace oxidizing slag mortar using MNLR and BPN

  • Kuo, Wen-Ten;Juang, Chuen-Ul
    • Computers and Concrete
    • /
    • v.20 no.1
    • /
    • pp.111-118
    • /
    • 2017
  • The present study established prediction models based on multiple nonlinear regressions (MNLRs) and backpropagation neural networks (BPNs) for the expansion of cement mortar caused by oxidization slag that was used as a replacement of the aggregate. The data used for the models were obtained from actual laboratory tests on specimens that were produced with water/cement ratios of 0.485 or 1.5, within which 0%, 10%, 20%, 30%, 40%, or 50% of the cement had been replaced by oxidization slag from electric-arc furnaces; the samples underwent high-temperature curing at either $80^{\circ}C$ or $100^{\circ}C$ for 1-4 days. The varied mixing ratios, curing conditions, and water/cement ratios were all used as input parameters for the expansion prediction models, which were subsequently evaluated based on their performance levels. Models of both the MNLR and BPN groups exhibited $R^2$ values greater than 0.8, indicating the effectiveness of both models. However, the BPN models were found to be the most accurate models.

Effect of Resorcinol as Free Formaldehyde Scavenger for Fabric Finished with Urea-formaldehyde Precondensate. (Urea-Formaldehyde 수지가공포에 있어 Resorcinol의 유리 Formaldehyde 포착효과)

  • Kang, In-Sook;Kim, Sung-Reon
    • Textile Coloration and Finishing
    • /
    • v.9 no.2
    • /
    • pp.41-49
    • /
    • 1997
  • To control free formaldehyde release from fabric finished with N-methylol compounds, resin finished cotton fabric was treated with resorcinol solution, dried and cured. Factors affecting to control formaldehyde release have been investigated. It was shown that the aftertreatment with resorcinol greatly suppressed the free formaldehyde release. Up to concentration of about 5% of resorcinol, the concentration of resorcinol effected on the control of free and evolved formaldehyde. And at high concentration of resorcinol, however, the concentration became rather insensitive to contol formaldehyde release. Addition of some salt catalysts such as ammonium chloride, zinc nitrate, sodium acetate and ammonium acetate, was effective in decreasing formaldehyde release. Considering the effect on the control of formaldehyde and crease recovery, ammonium acetate was concidered to be the best catalyst. It was observed that the optimum curing temperature for the resorcinol treatment was about 15$0^{\circ}C$, and that the curing time did not affected formaldehyde release over three minutes. Although the treatment of resorcinol had a little adverse effect on crease recovery of resin finished fabric, this effect could be negligible.

  • PDF

Electrical Characteristics of Isotropic Conductive Adhesives (ICAs) for the Fabrication of RFID Inlays (RFID Inlay 제작용 등방성 도전 접착제의 전기적 특성 평가)

  • Lee, Jun-Sik;Kim, Jun-Ki;Kim, Mok-Soon;Lee, Jong-Hyun
    • Korean Journal of Metals and Materials
    • /
    • v.47 no.7
    • /
    • pp.447-453
    • /
    • 2009
  • Isotropic conductive adhesives (ICAs) have been used or considered as an interconnect material for radio frequency identification (RFID) inlays or other flip chip assemblies due to the advantages of having a low temperature and high-speed bonding. In this work, the curing properties of commercial ICAs for the RFID tag application and the signal transmission in conductive lines that contained the ICA joints were evaluated as a function of the degree of cure at 900 MHz frequency range. The ICAs showed adequate signal transmission only after the curing process passed over the critical time. It was also found that the insertion loss of signal was more dependent on the contact states of Ag fillers in the bondline in preference to the electrical resistance of the ICA itself.