• 한국산업융합학회 논문집
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• 제10권2호
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• pp.73-80
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• 2007

The preparation of oil absorbent using waste polyurethane was studied. And the effects of shape, size, and contents of waste polyurethane foam was investigated. The waste foam was treated in shape of powder, cube and bar type generated from rigid sandwich panel process. The tests for flexural strength, combustibility, and water absorptivity were carried out to investigate the mechanical and physical properties of the recycled foams. And the cell microstructure was evaluated through Scanning Electron Micrograph. The recycled foam containing powder-shaped underfilled and showed poor properties that was generated through reactivity of the resins and increasing of slurry viscosity. For the recycled foam with the cube and bar-shaped, the underfilling was caused by interference between the waste PUFs and increasing surface areas of PUF. Low cell density, non-uniformity of cell shape and size, and low adhesion of the boundary surface (new/recycled) was showed as a result of the poor properties. Considering underfilling and the properties of PUF (new/recycled), maximum recycle contents were less than 20 wt% for the powder and above 40 wt% for the cube and bar.

• 한국재료학회지
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• 제27권12호
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• pp.688-694
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• 2017

Porous materials such as polymeric foam are widely adopted in engineering and biomedical fields. Porous materials often exhibit complex nonlinear behaviors and are sensitive to material and environmental factors including cell size and shape, amount of porosity, and temperature, which are influenced by the type of base materials, reinforcements, method of fabrication, etc. Hence, the material characteristics of porous materials such as compressive stress-strain behavior and void volume fraction according to aforementioned factors should be precisely identified. In this study, unconfined uniaxial compressive test for two types of closed-cell structure polyurethane foam, namely, 0.16 and $0.32g/cm^3$ of densities were carried out. In addition, the void volume fraction of three different domains, namely, center, surface and buckling regions under various compressive strains (10 %, 30 %, 50 % and 70 %) were quantitatively observed using Micro 3D Computed Tomography(micro-CT) scanning system. Based on the experimental results, the relationship between compressive strain and void volume fraction with respect to cell size, density and boundary condition were investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.491-495
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• 2004

The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.81.2-81.2
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• 2011

The gas diffusion layer (GDL) consists of two main parts, the GDL backing layer, called as a substrate and the micro porous layer (MPL) coated on the GDBL. In this process, carbon particles of MPL penetrates to the GDBL consequently forms MPL penetration part. In this study, the micro porous layer (MPL) penetration thickness is determined as a design parameter of the GDL which affect pore size distribution profile through the GDL inducing different mass transfer characteristics. The pore size distribution and water permeability characteristics of the GDL are investigated and the cell performance is evaluated under fully/low humidification conditions. Transient response and voltage instability are also studied. In addition, to determine the effects of MPL penetration on the degradation, the carbon corrosion stress test is conducted. The GDL that have deep MPL penetration thickness shows better performance in high current density region because of enhanced water management, however, loss of penetrated MPL parts is shown after aging and it induces worse water management characteristics.

• 한국재료학회지
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• 제27권12호
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• pp.664-671
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• 2017

A composite material was prepared for the bipolar plates of phosphoric acid fuel cells(PAFC) by hot pressing a flake type natural graphite powder as a filler material and a fluorine resin as a binder. Average particle sizes of the powders were 610.3, 401.6, 99.5, and $37.7{\mu}m$. The density of the composite increased from 2.25 to $2.72g/cm^3$ as the graphite size increased from 37.7 to $610.3{\mu}m$. The anisotropy ratio of the composite increased from 1.8 to 490.9 as the graphite size increased. The flexural strength of the composite decreased from 15.60 to 8.94MPa as the graphite size increased. The porosity and the resistivity of the composite showed the same tendencies, and decreased as the graphite size increased. The lowest resistivity and porosity of the composite were $1.99{\times}10^{-3}{\Omega}cm$ and 2.02 %, respectively, when the graphite size was $401.6{\mu}m$. The flexural strength of the composite was 10.3MPa when the graphite size was $401.6{\mu}m$. The lowest resistance to electron mobility was well correlated with the composite with lowest porosity. It was possible the flaky large graphite particles survive after the hot pressing process.

• Elastomers and Composites
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• 제50권4호
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• pp.297-303
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• 2015

Ammonium polyphosphate-polyurethane foam composite (APP-PUF) was prepared from poly(adipate)diol/ammonium polyphosphate composite (f = 2), polyether polyol (f = 4.6), and PMDI (f = 2.5). As a blowing agent, $H_2O$ was used at various concentrations. The thermal decomposition behavior, morphology, closed-cell content, and density of APP-PUF were characterized. At the $H_2O$ concentrations lower than 3.5 php, the cell size of pure polyurethane foams (PUF) and APP-PUFs were close each other. As the $H_2O$ concentration became greater than 5.0 php, the cell size of the PUFs greatly increased compared to that of APP-PUFs. Addition of 1.5~1.9 wt% ammonium polyphosphate to the PUFs greatly enhanced the thermal stability of the PUFs, so 50 wt% residual temperature of APP-PUFs increased to $380{\sim}488^{\circ}C$, which were $30{\sim}70^{\circ}C$ higher than those of the PUFs. Thermal stability of the PUFs and APP-PUFs increased with $H_2O$ content and then decreased once $H_2O$ content exceeded 5 php.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.163-166
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• 1997

Aluminium foam material is a highly porous material having complicated cellular structure defined by randomly distributed air pores in metallic matrix. this structure gives the aluminium a set of properties which cannot be achieved by any of conventional treatments. The properties of aluminium foam material significantly depend on its porosity, so that a desired profile of properties can be tailored by changing the foam density. Melting method is the one of foaming processes, which the production has long been considered difficult to realize becaues of such problems as the low foamability of molten metal, the varying size of. cellular structures, solidification shrinkage and so on. These problems, however, have gradually been solved by researchers and some manufacturers are now producing foamed aluminum by their own methods. Most of all, the parameters of solving problem in electric furnace were stirring temperature, stirring velocity, foaming temper:iture, and so on. But it has not considered about those in induction heating, foaming velocity and foaming temperature in semi-solid state yet. Therefore, this paper presents the effects on these parameter to control cell size, quantity and distribution.

• Carbon letters
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• 제4권3호
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• pp.121-125
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• 2003

The Pt-Ru/Carbon as an anode catalyst supported on the commercial activated carbon (AC) having high surface area and micropore was characterized for application of Direct Methanol Fuel Cell (DMFC). The Pt-Ru/AC anode catalyst used in this experiment showed the performance of $600\;mA/cm^2$ current density at 0.3 V. The borohydride reduction process using $NaBH_4$, denoted as a process A, showed much higher current and power densities than process B prepared by changing the reduction and washing process of process A. The particle sizes are strongly affected by the reduction process than the specific surface area of raw active carbon and the sizes are almost constant when the specific surface area of carbon are over than the $1200\;m^2/g$. Smaller particle size of catalyst and more narrow intercrystalite distance increased the performance of DMFC.

• 한국가스학회지
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• 제5권4호
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• pp.79-84
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• 2001

본 연구에서는 폴리올의 구조(OH-value, functionality)와 각각의 발포제(CFC-11, HCFC-l4lb, HFC-365mfc)가 우레탄의 반응성, 폼의 물성 그리고 cell 구조에 미치는 영향을 평가하여 HFC-365mfc의 대체 가능성을 고찰하였다. 그 결과 폴리올의 OH-value와 작용기가 증가함에 따라 반응온도, 반응속도, 밀도 그리고 압축강도는 증가하였다. Cell의 크기는 폴리올의 OH-value와 작용기가 커질수록 미세하게 형성되었다. CFC-11 HCFC-l4lb 그리고 HFC-36smfc에 따른 반응온도, 반응속도, 밀도 그리고 압축강도의 변화는 거의 없었으며, cell 분포는 HFC-365mfc를 사용한 경우가 HCFC-l4lb를 사용한 경우에 비해 균일한 cell 분포를 나타내었다.

• 한국식품과학회지
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• 제20권4호
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• pp.463-469
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• 1988

쌀가루의 압출성형 특성을 조사하기 위하여 원료의 수분합량과 입자크기를 달리하여 자가발열형 single screw extruder로 처리하고 이때 온도변화에 따른 extrudate의 물성학적인 성질을 비교하였다. 원료의 수분함량은 17%, 19%, 22%, 25%, 28%로 했고 입자크기는 18-60mesh와 60-120mesh의 두 범위로 했다. 내부흐름의 온도는 자동 온도기록계에 기록되게 하여 정상상태 가동이 될 때까지 경시적으로 시료를 채취하였다. 팽화율은 수분함량과 입자크기가 감소함에 따라 증가하였으며, bulk density는 팽화율과 역상관 관계를 나타내었다. Extrudate의 절단력은 수분함량이 적고 입자조기가 감소함에 따라 낮아졌으며 기공의 크기도 균일하였다. 색도는 수분함량과 입자크기가 증가함에 따라 명도는 증가하였고 황색도는 감소하였다. 겉보기 점도는 수분함량이 증가함에 따라 증가했고, 수용성 지수는 감소하였다. 원료의 수분이 감소함에 따라 일부의 전분은 호정화를 유발하는 것으로 판단되었다.