• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1396-1403
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• 2016

In this study, fast-curing shielding materials were prepared with a two-component polyurethane matrix and a filler material of PbO through a one-step, laboratory-scale method. With an increase in the filler content, viscosity increased. However, the two components showed a small difference. Curing time decreased as the filler content increased. The minimum tack-free time of 27 s was obtained at a filler content of 70 wt%. Tensile strength and compressive strength initially increased and then decreased as the filler content increased. Even when the filler content reached 60 wt%, mechanical properties were still greater than those of the matrix. Cohesional strength decreased as the filler content increased. However, cohesional strength was still greater than 100 kPa at a filler content of 60 wt%. The ${\gamma}$-ray-shielding properties increased with the increase in the filler content, and composite thickness could be increased to improve the shielding performance when the energy of ${\gamma}$-rays was high. When the filler content was 60 wt%, the composite showed excellent comprehensive properties.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.33-39
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• 2010

The moisture absorption properties such as diffusion coefficient and moisture content ratio of liquid type epoxy resin systems with the filler were investigated. Bisphenol A type and Bisphenol F type epoxy resin, Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these liquid type epoxy encapsulant according to the change of filler size. The temperature of glass transition (Tg) of these epoxy resin systems was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these epoxy resin systems according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these systems were calculated in terms of modified Crank equation based on Ficks' law. An increase of Tg and diffusion coefficient with filler size in these systems can be observed, which are attributed to the increase of free volume with Tg. The change of maximum moisture absorption ratio according to the filler size and filler content cannot be observed; however, the diffusion coefficients of these systems decreased with filler content. The diffusion via free volume is dominant in the epoxy resin systems with low nano-sized filler content; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the liquid type epoxy encapsulant with high nano-sized filler content.

• 펄프종이기술
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• 제45권1호
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• pp.59-66
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• 2013

Fillers have been used for printing paper to improve printability, sheet formation and optical properties and to reduce production costs by replacing expensive wood pulps. However, an increased filler content will decrease paper strength because filler particles interfere with fiber-fiber bonding. In order to increase filler content without sacrificing too much paper strength in high filler content papers, the surface of precipitated calcium carbonate (PCC) has been modified by adsorbing anionic polyacrylamide and cationic starch in series. The adsorbed polymer layers would enhance interactions between the filler surface and the fiber surface, improving internal bonding. It was found that the modified PCC increased paper strength at a given filler content compared to the coventional method. Negligible differences in optical properties and formation of paper, filler and fines retention and drainage on the wire section were observed between the modified and the conventional PCC. However, the decreased bulk of paper was observed when the modified PCC was used.

• Elastomers and Composites
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• 제36권1호
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• pp.37-43
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• 2001

실리카와 카본블랙으로 보강된 SBR 배합물의 가황 특성과 bound rubber 함량 그리고 가황물의 물성에 보강제의 조성비가 미치는 영향을 연구하였다. 고무 배합물의 보강제 총 함량은 80.0 phr 이다. Bound rubber 함량은 실리카 함랑비가 증가할수록 증가하였고 점도 역시 증가하였는데, 특히 실리카 함량이 60.0 phr 이상일 때는 점도의 증가폭이 두드러지게 높아졌다. 가황시간은 실리카 함량이 증가할수록 느려졌고 가황 속도도 느려졌다. 실리카 함량비가 증가할수록 델타 토크가 증가함에도 불구하고 모둘러스는 감소하는 경향을 보였다. $60^{\circ}C$에서의 tan ${\delta}$ 값은 실리카 함량이 증가할수록 감소하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.209-211
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• 1996

The dielectric breakdown characteristics of DGEBA/MDA/SN system filled with $Al_2O_3$ under AC high electric field were investigated. As the filler content increased, the dielectric breakdown strength increased, but decreased at higher filler content than 5 phr. The probability of defects such as air bubbles, peel between filler and epoxy resin insulator, etc. increase proportionally to filler contents. Fillers blockade the treeing growth and relax the electric field at the tip of electrical tree and the treeing propagation rate decreases so that the strength showed higher strength at lower filler content than 5 phr.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.1
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• pp.85-90
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• 2006

Increasing the filler content of sheet improves the optical properties and printability of paper and provides an opportunity for saving production cost through fiber replacement with relatively low-priced filler. But increasing the filler content tends to decrease the strength of paper and filler retention. It also tends to deteriorate drainage on the paper machine. To overcome these problems, preflocculation technology of fillers may be employed. Many research efforts have been made on the properties of preflocculated filler, namely prefloc, whose size and size distribution were influenced by polymer type and shear level. But there is much to be investigated about the effect of the prefloc characteristics on the physical properties of paper. To evaluate the effect cationic polymers on the size and size distribution of preflocculated GCC and their shear stability, cationic PAM and cationic starch were used. The influence of the preflocculation on filler retention and its surface distribution, and the changes of physical and optical properties of handsheets affected by the characteristics of preflocs were examined. Filler distribution on sheet surface was also analyzed by EPMA. Results showed that cationic PAM formed large preflocs at low dosage. Cationic starch was required to add 15 times as much as cationic PAM to obtain the preflocs with similar size. But preflocs formed with cationic starch was superior in shear stability to those formed with cationic PAM. Filler preflocculation technology could provide an opportunity of increasing filler content significantly without loss in tensile strength. And increased filler contents could compensate brightness loss which often accompanies filler preflocculation. When excessively large preflocs were used, however, brightness loss rather than the improvement in tensile strength was predominant. Therefore it is of great importance to produce preflocs with proper size and shear stability for maximizing the improvement of physical properties of papers.

• 마이크로전자및패키징학회지
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• 제6권3호
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• pp.51-63
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• 1999

무기 충전제를 고충전시킨 에폭시 수지 조성물이 반도체 패키지의 신뢰성에 미치는 영향을 검토하였다. Ouchiyama 등의 모델로부터 최대충전밀도를 향상시킴으로써 고충전을 달성할 수 있는 방법을 제시할 수 있었으며, 최대충전밀도가 증가함에 따라 에폭시 수지 조성물의 점도가 감소하였고, 흐름성이 개선되었다. 충전제 함량이 증가함에 따라 흡습 특성이 향상되었고 열팽창계수를 낮춤으로써 저응력화를 달성할 수 있었으나, 임계 충전제 함량 이상에서는 금속 리드프레임과의 접착강도가 저하되었다. 따라서 에폭시 수지 조성물의 균형 있는 신뢰 특성을 얻기 위해서는 충전제 함량을 적정하게 선택해야 하며, 충전량을 더욱 높여 고신뢰성을 얻기 위해서는 최적의 충전제 조합을 선정하여야 함을 알 수 있었다.

• 마이크로전자및패키징학회지
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• 제10권3호
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• pp.9-17
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• 2003

In this paper, thermo-mechanical and rheological properties of NCPs (Non-Conductive Pastes) depending on silica filler contents and diluent contents were investigated. And then, thermal cycling (T/C) reliability of flip chip assembly using selected NCPs was verified. As the silica filler content increased, thermo-mechanical properties of NCPs were changed. The higher the silica filler content was added, glass transition temperature ($T_g$) and storage modulus at room temperature became higher. While, coefficient of thermal expansion (CTE) decreased. On the other hand, rheological properties of NCPs were significantly affected by diluent content. As the diluent content increased, viscosity of NCP decreased and thixotropic index increased. However, the addition of diluent deteriorated thermo-mechanical properties such as modulus, CTE, and $T_g$. Based on these results, three candidates of NCPs with various silica filler and diluent contents were selected as adhesives for reliability test of flip chip assemblies. T/C reliability test was performed by measuring changes of NCP bump connection resistance. Results showed that flip chip assembly using NCP with lower CTE and higher modulus exhibited better T/C reliability behavior because of reduced shear strain in NCP adhesive layer.

• Carbon letters
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• 제15권4호
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• pp.255-261
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• 2014

Multi-walled carbon nanotube reinforced epoxy composites were fabricated using shear mixing and sonication. The mechanical, viscoelastic, thermal, and electrical properties of the fabricated specimens were measured and evaluated. From the images and the results of the measurements of tensile strengths, the specimens having 0.6 wt% nanotube content showed better dispersion and higher strength than those of the other specimens. The Young's moduli of the specimens increased as the nanotube filler content was increased in the matrix. As the concentrations of nanotubes filler were increased in the composite specimens, their storage and loss moduli also tended to increase. The specimen having a nanotube filler content of 0.6 wt% showed higher thermal conductivity than that of the other specimens. On the other hand, in the measurement of thermal expansion, specimens having 0.4 and 0.6 wt% filler contents showed a lower value than that of the other specimens. The electrical conductivities also increased with increasing content of nanotube filler. Based on the measured and evaluated properties of the composites, it is believed that the simple and efficient fabrication process used in this study was sufficient to obtain improved properties in the specimens.

• 펄프종이기술
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• 제47권1호
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• pp.84-92
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• 2015

Fillers have been used to improve the optical and printing properties and to reduce the production cost while increasing the filler content in paper causes adverse effects on paper strength. In the previous study, it was shown that the thick stock addition of filler can increase the filler content without significantly sacrificing paper strength. This study was carried out to elucidate the effect of the location of starch addition (before or after the filler addition) on handsheet properties and a papermaking process as a part of developing the thick stock loading technology. In addition, effects of dual flow addition of cationic starch were evaluated. It was found that paper strength was superior when cationic starch was added after the filler addition. No adverse effects on optical properties, formation and filler retention were observed. Drainage was a bit slower when starch was added after the filler addition, which shall be resolved with regulating other factors. Dual flow addition of cationic starch before and after filler addition did not show any special advantage.