• Elastomers and Composites
• /
• 제50권4호
• /
• pp.265-273
• /
• 2015

In this work, the emulsified asphalt with high phase stability and storage stability was prepared by using phase inversion emulsification and the surfactant mixed with cationic and nonionic surfactants. It was found that the asphalt together with Span 20, nonionic surfactant and DDA (Dimethyl Dodecyl Amine), cationic surfactant showed the most stable phase. The phase stability of the emulsified asphalt, therefore, was investigated through the particle size with mixed surfactant content, rheology behavior and Zeta potential value; the particle size decreased with the increase of the mixed surfactant content but the viscosity increased. The shear thinning behaviors and the Zeta potential value with 50 mV~60 mV were shown, which was found to be considered stable. In addition, SBR latex(Styrene-butadiene-rubber) and water dispersed Epoxy (EPD) were used to enhance the physical properties of the emulsified asphalt. The swelling and adhesion features of the emulsified asphalt were also studied with $CaCO_3$, Silica, and Montmorillonite (MMT). It was shown that the addition of SBR latex and MMT can be another way to improve the physical properties of the emulsified asphalt in that the lowest swelling feature was found.

• 한국세라믹학회지
• /
• 제49권6호
• /
• pp.518-522
• /
• 2012

Hyaluronic acid (HA) microbeads were synthesized by dropping 0.5 wt% of sodium hyaluronate dissolved in NaOH into 0.2 vol% of divinyl sulfone dissolved in 2-methyl-1propanol at a speed of 0.005 ml/min. HA microbeads were collected from a divinyl sulfone crosslinker solution stirred at 200 to 400 rpm for 5 h at temperatures from room temperature to $60^{\circ}C$ at intervals of $10^{\circ}C$. The crosslinked microbeads were then cleaned thoroughly using distilled water and ethanol. SEM results revealed that the microbeads were white-colored spheres. The 3-D porous network structure of the microbeads became dense with an increase in the crosslinking temperature; however, no dependence of the crosslinking temperature on the microbead size was detected. The extent of swelling decreased from 970% to 670% with an increase in the crosslinking temperature from room temperature to $60^{\circ}C$, most likely due to the increase in the degree of crosslinking.

• Nuclear Engineering and Technology
• /
• 제55권1호
• /
• pp.80-99
• /
• 2023

This paper presents the results of investigating the change in welding residual stresses of the core shroud, which is one of subcomponents in reactor vessel internals, performing finite element analysis. First, the welding residual stresses of the core shroud were calculated by applying the heat conduction based lumped pass technique and finite element elastic-plastic stress analysis. Second, the temperature distribution of the core shroud during the normal operation was calculated by performing finite element temperature analysis considering gamma heating. Third, through the finite element viscoelastic-plastic stress analysis using the calculated temperature distribution and setting the calculated residual stresses as the initial stress state, the variation of the welding residual stresses was derived according to repeating the normal operation. In the viscoelastic-plastic stress analysis, the effects of neutron irradiation on mechanical properties during the cyclic normal operations were considered by using the previously developed user subroutines for the irradiation agings such as irradiation hardening/embrittlement, irradiation-induced creep, and void swelling. Finally, the effect of neutron irradiation on the welding residual stresses was analysed for each irradiation aging. As a result, it is found that as the normal operation is repeated, the welding residual stresses decrease and show insignificant magnitudes after the 10^th refueling cycle. In addition, the irradiation-induced creep/void swelling has significant mitigation effect on the residual stresses whereas the irradiation hardening/embrittlement has no effect on those.

• Journal of the Korean Wood Science and Technology
• /
• 제29권2호
• /
• pp.109-117
• /
• 2001

한지(韓紙) 제조(製造) 공정(工程) 중에서 발생하는 백색 슬러지와 흑색 슬러지를 각각 일정비율(10, 20, 30, 40%)로 목재(木材) 파티클과 혼합(混合)하고 PMDI, 요소 및 페놀수지를 이용하여 각각 목표비중(目標比重) 0.60, 0.75, 0.90 별로 복합(複合)보드를 제조(製造)하여 물리적(物理的) 성질(性質)을 측정 분석한 결과 흡수길이변화율은 대조보드에 비해 크게 증가하지 않았으며 흡수두께팽창율은 PMDI를 적용한 백색 슬러지 목재(木材) 파티클 복합(複合)보드가 가장 낮은 값을 보였고 흡수율은 흑색 슬러지 목재(木材) 파티클 복합(複合)보드의 경우 혼합(混合) 비율(比率)이 증가할수록 대체로 감소하는 경향을 보였다.

• Journal of the Korean Wood Science and Technology
• /
• 제29권3호
• /
• pp.36-46
• /
• 2001

This study was to find a way of reusing wood and plastic wastes, which considered as a troublesome problem to be solved in this age of mass production and consumption, in manufacturing wood fiber-polypropylene fiber composite panel. And the feasibility of this composite panel as a substitute for existing headliner base panel of automobile was also discussed, especially based on physical and mechanical performance. Nonwoven web composite panels were made from wood fiber and polypropylene fiber formulations of 50 : 50, 60 : 40, and 70 : 30, based on oven-dry weight, with densities of 0.4, 0.5, 0.6, and 0.7 g/$cm^3$. At the same density levels, control fiberboards were also manufactured for performance comparison with the composite panels. Their physical and mechanical properties were tested according to ASTM D 1037-93. To elucidate thickness swelling mechanism of composite panel through the observation of morphological change of internal structures, the specimens before and after thickness swelling test by 24-hour immersion in water were used in scanning electron microscopy. Test results in this study showed that nonwoven web composite panel from wood fibers and polypropylene fibers had superior physical and mechanical properties to control fiberboard. In the physical properties of composite panel, dimensional stability improved as the content of polypropylene fiber increased, and the formulation of wood fiber and polypropylene fiber was considered to be a significant factor in the physical properties. Water absorption decreased but thickness swelling slightly increased with the increase of panel density. In the mechanical properties of composite panel, the bending modulus of rupture (MOR) and modulus of elasticity (MOE) appeared to improve with the increase of panel density under all the tested conditions of dry, heated, and wet. The formulation of wood fiber and polypropylene fiber was considered not to be a significant factor in the mechanical properties. All the bending MOR values under the dry, heated, and wet conditions met the requirements in the existing headliner base panel of resin felt.

• Geomechanics and Engineering
• /
• 제2권3호
• /
• pp.191-202
• /
• 2010

The porosity (including the specific surface area and pore volume-diameter distribution) of montmorillonitic soft rock (MSR) was studied experimentally with an electrochemical treatment, based on which the change in porosity was further analyzed from the perspective of its electrokinetic potential (${\zeta}$ potential) and the isoelectric point of the electric double layer on the surface of the soft rock particles. The variation between the ${\zeta}$ potential and porosity was summarized, and used to demonstrate that the properties of softening, degradation in water, swelling, and disintegration of MSR can be modified by electrochemical treatment. The following conclusions were drawn. The specific surface area and total pore volume decreased, whereas the average pore diameter increased after electrochemical modification. The reduction in the specific surface area indicates a reduction in the dispersibility and swelling-shrinking of the clay minerals. After modification, the ${\zeta}$ potential of the soft rock was positive in the anodic zone, there was no isoelectric point, and the rock had lost its properties of softening, degradation in water, swelling, and disintegration. The ${\zeta}$ potential increased in the intermediate and cathodic zones, the isoelectric point was reduced or unchanged, and the rock properties are reduced. When the ${\zeta}$ potential is increased, the specific surface area and the total pore volume were reduced according to the negative exponent law, and the average pore diameter increased according to the exponent law.

• 한국문화재보존과학회:학술대회논문집
• /
• 한국문화재보존과학회 2001년도 제14회 발표논문집
• /
• pp.59-67
• /
• 2001

• 공업화학
• /
• 제28권1호
• /
• pp.57-63
• /
• 2017

본 연구에서는 다양한 NCO index에서 물 함량 변화가 자동차용 폴리우레탄 시트 폼 패드의 정적 안락감에 미치는 영향을 알아보았다. 정적 안락감에 영향을 미치는 요인을 파악하기 위해 UTM을 사용한 정하중 특성 시험을 통하여 히스테리시스 곡선을 나타냈으며, 이를 통해 25% 변형 시 경도와 65% 변형 시 경도, hysteresis loop area, hysteresis loss (%), 그리고 Sag factor를 구하였다. 동일한 NCO index에서 물 함량이 증가함에 따라 우레아 결합의 증가로 경도가 증가하고, 가교밀도가 증가하는 경향을 swelling ratio 측정으로 확인하였으며, 이에 따라 복원력은 감소하는 경향을 확인하였다. 또한 표면 경도의 증가로 인해 Sag factor가 감소하는 경향을 확인하였다. 동일한 물 함량에서 NCO index가 증가함에 따라 우레탄과 우레아 결합이 이소시아네이트와 추가 반응하여 가교도와 경도가 증가하고 이에 따라 복원력이 감소함을 확인하였다.

• Journal of the Korean Wood Science and Technology
• /
• 제22권2호
• /
• pp.30-36
• /
• 1994

Steam explosion process is one of the most efficient, pretreatment method for the utilization of lignocellulosic biomass. The carbxymethyl-cellulose(CMC) was prepared with steam exploded wood(EXW), pine(Pinus densiflora) and oak(Quercus mongolica), by standard method using isopropyl alcohol and monochloroacetic acid. The range of water solubility of carboxymethylated pine exploded wood was 45.2~66.8 % and those of oak was 60.7~84.7 %. The degree of substitution(D.S) of carboxymethylated pine exploded wood was 0.11~0.33 and oak exploded wood was 0.48~0.76. The color of carboxymethylated pine and oak exploded wood was brown-black. When carboxymethylated EXW was purified by sulfuric acid, the yield of carboxymethylated wood was lower than non-treated one. However, the color was still brown-black although after delignification. In carboxymethylated EXM prepared after delignification, the water solubility and degree of substitution(D.S) of pine were 81.4~95.9 % and 0.71~0.79, and those of oak were 76.2~89.5 % and 0.79~1.05. The values were higher than non-treated. The degree of substitution of purified carboxymethylated wood prepared with delignified EXM, pine and oak were 0.50~0.71 and 0.70~0.88. The color of carboxymethylated wood was white. In carboxymethylated wood preparde after delignification of EXM, swelling ratio and water retention value of pine were 95.9~96.5 and 580.0~751.2, those of oak were 76.2~89.5 and 124.3~307.6.

• 한국전산구조공학회논문집
• /
• 제17권4호
• /
• pp.413-421
• /
• 2004

본 논문에서는 깊은 지하 500m에 처분된 가압경수로(PWR) 고준위폐기물 처분용기에 지하수압과 벤토나이트 팽윤압이 가해지는 동안 처분용기에 발생하는 크립변형을 예측하기 위하여 처분용기에 대한 구조해석을 수행하였다. 보통 이러한 크립변형은 처분용기에 추가적인 외력이 작용하지 않더라도 처분용기에 작용하는 압력과 내부의 높은 열에 의하여 발생될 수 있다. 처분용 기내부의 열분포의 복잡성 덴 시간의존성으로 인하여 일단 외부 지하수압 및 팽윤압만 고려하여 크립해석을 수행하였다. 이를 위하여 적당한 크립함수를 사용하였으며, 해석은 1억$(10^8)$초 동안 수행하였다. 해석결과 1억초 동안 발생하는 크립 변형률은 매우 작으며 주희 처분용기의 위아래 덮개에 발생함을 알 수 있었다. 그러나 처분용기의 구조강도에 중요한 내부 주철삽입물에는 훨씬 더 작은 미소한 변형률만 발생하여 처분용기에 발생하는 크립변형은 처분용기의 구조적인 안전성에는 큰 영향을 미치지 않음을 알 수 있었다. 해석 초기에 처분용기 내에 급격히 응력이 증가하여 최고치에 도달한 후 잠깐동안 이 응력 값을 유지하다가 그 이 후에는 급격히 응력 값이 감소하는 응력이완현상을 보이고 있기 때문에 발생 응력 측면에서도 전혀 처분용기의 구조적인 안전성에 문제가 없음이 확인되었다.