• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.373-373
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• 2006

Rigid polyurethane foams(PUFs) are widely used in most areas of insulations such as storage tank and pipe line for transporting liquefied gas. Glass fiber and nanoclay are used for improvement in mechanical property and thermal insulation of rigid PUF at very low temperature(<$-150^{\circ}C$). These rigid PUFs have been characterized in terms of thermal, mechanical, dynamic mechanical properties and cell morphology. It was found that mechanical properties, thermal conductivity and dimensional stability of rigid PU foams were improved by glass fiber and nanoclay.

• Transactions on Electrical and Electronic Materials
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• v.2 no.2
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• pp.32-36
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• 2001

A new solid source for low temperature diffusion into silicon was developed. The source wafer consists of an “active” compound, which is sol-gel prepared phosphosilicate glass-ceramics containing 56% P$_2$O$\sub$5/, embedded in a skeletal foam-like, inert substrate. Phosphorus diffusion from the new solid sources at low temperatures (800-875$^{\circ}C$) produced reprodecible sheet resistances and shallow junctions. From a series of one hour doping runs, the life time of the phosphosilicate source was determined to be over 40 hours. The effective diffusion coefficient of phosphorus into silicon and the corresponding activation energy at 850$^{\circ}C$ were determined to be 7.5${\times}$10$\^$-15/ $\textrm{cm}^2$/sec and ∼3.9 eV, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.448-455
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• 2018

Glass wool is an eco-friendly materials that is manufactured through a continuous process by processing waste glass. This materials is low cost compared with another materials and has excellent thermal conductivity. For this reason, glass wool is installed as insulation system for LNG carriers and as insulation of building wall as well as various industries. The mechanism of insulation of glass wool is the conduction of the wool itself and convection by space between fibers. Therefore, in order to develop the enhanced thermal conductivity of glass wool is necessary to reduce its own conduction or to insert additional material after manufacturing as well as prevent convection. In this respect, many researchers have been actively studying to decrease thermal conductivity of polyurethane foam using by inserted glass wool or change the chemical component of glass wool. However, many research are aiming reduction of glass wool itself. This study focus on post-processing and inserted different materials; silica-aerogel, kevlar fiber 1mm, 6mm and glass bubble. Experimental results show that the thermal conductivity almost decreases with the addiction of glass bubble and silica aerogel.

• Composites Research
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• v.12 no.6
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• pp.74-82
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• 1999

The static and fatigue characteristics of polyurethane foam cored sandwich structures are investigated. Three types of the specimens with the glass fabric faces and the polyurethane foam core are used; non-stitched. stitched, and stiffened sandwich specimen. Especially additional structural reinforcements with the twisted polyester and glass fiber for thickness direction are made to stitched sandwich structure panel to minimize the delamination of structure which is stitched the upper and lower faces through the core and the resin is impregnated Into stitched fiber with the characteristics of low viscosity of resin at resin flow temperature and cured together with during the curing process. Bending strength of stitched specimen which is 50 mm $50{\times}50{\;}mm$ pitched is improved by 50 % as com-pared with non-stitched specimen and stiffened specimen is improved 10 times more than non-stitched structure. After fatigue testing of $10^6$cycles by 20% of ultimate load under monotonic load, the bending fatigue strength of non-stitched specimen is decreased by 27% of monotonic bending strength, 39% for stitched structure and 20% for stiffened specimen. To verify the aging effect of polyurethane form core, Ultrasonic C-scanning equipment is used to detect the damage of skin laminate alone after fatigue test. From results of UT C-scan images, there is no defect that can be damaged occurred during fatigue test. It is concluded that the decrease of bending strength for foam cored sandwich specimen is caused by the decrease of stiffness due to the aging of polyurethane foam core during fatigue cycles.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1996.11a
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• pp.57-61
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• 1996

Our goal was to make a cost-effective automatic fire extinguishing system for the engine compartment use of automobiles. We designed this system for the engine compartment. This system consists of 1)foam extinguisher, 2)four nozzles, 3)a pipe arrangement, and 4)an extinguishing device which is equipped with a glass bulb as detector. First and foremost, the extinguishing device was carefully designed to keep the system cost to a minimum. Second, a AFFF foam extinguisher was used because no other fire-fighting agents proved effective against fire in the engine compartment. The AFFF(Aqueous Film Forming Foam) agent which was used in the extinguisher is the 3M company's Light Water. We sought, however, to make other foams by using Halon 1301 and Halon alternatives such as HCFC Blend A, HFC-227ea. We selected these alternatives instead of air in order to raise the expansion ratio of the AFFF agent. By these means we discovered that it is possible to increase the expansion ration of the AFFF agent up to 44:1. We then demonstrated that our automatic fire extinguishing system is the most effective and lowest cost-system yet devised for passenger cars.

• Elastomers and Composites
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• v.46 no.2
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• pp.158-163
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• 2011

Rigid polyurethane foam (PUF) was synthesized with different contents of aliphatic polyester polyol, aromatic polyester polyol and aliphatic polyether polyol to know change of properties under sea water. UTM(universal testing machine), DSC(differential scanning calorimetry), hardness meter and FT-IR(Fourier transform spectroscopy) were used to study the PUF`s physical properties under sea water. Compressive strength and hardness of PUF decreased with increasing the content of aromatic polyester polyol under sea water as aging. According to the results of IR spectral analysis, reduction of urethane and urea peak was found and allophanate and biuret peak increased. Although glass transition temperature of PUF increased, mechanical properties of PUF decreased under sea water, because PUF gets brittle when crosslink density increase.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.247-254
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• 2008

Resilient materials are generally used for the floating floors to reduce the floor impact sound. Dynamic stiffness of resilient material, which has the most to do with the floor impact sound reduction. The resilient materials available in Korea include EPS(styrofoam), recycled urethane types, EVA(ethylene vinylacetate) foam rubber, foam PE(polyethylene). glass fiber & rock wool, recycled tire, foam polypropylene. compressed polyester, and other synthetic materials. In this study, we tested dynamic stiffness of resilient material and floor impact sound reduction characteristic to a lot of kinds of resilient materials. It was found that dynamic stiffness of multi-layered damping material could be estimated if know value of each layer that compose whole structure. And the test showed that the amount of the heavy-weight impact sound reduction appeared by being influenced from this dynamic stiffness of resilient material. The dynamic stiffness looked like between other resilient materials, a similar to the amount of the heavy-weight impact sound reduction was shown.

• Steel and Composite Structures
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• v.45 no.3
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• pp.467-482
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• 2022

One of the major failure modes in composite sandwich structures is the separation between skins and core. In this study, the effect of employing foam filled composite corrugated core on the skin/core debonding (resistance to separation between skin and core) is investigated both experimentally and numerically. To this aim, triangular corrugated core specimens are manufactured and compared with reference specimens only made of PVC foam core in terms of skin/core debonding under bending loading. The corrugated composite laminates are fabricated using the hand layup method. Also, the Vacuumed Infusion Process (VIP) is employed to join the skins to the core with greater quality. Utilizing an End Notched Shear (ENS) fixture, three point bending tests are performed on the manufactured sandwich composite panels. The results reveal that the resistance to separation capacity and flexural stiffness of sandwich composite has been increased about 170% and 76%, respectively by using a triangular corrugated core. The Cohesive Zone Model (CZM) with appropriate cohesive law in ABAQUS finite element software is used to model the progressive face/core interfaces debonding the difference between experimental and numerical results in predicting the maximum born load before the skin/core separation is about 6 % in simple core specimens and 3% in triangular corrugated core specimens.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.130-133
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• 2005

An experimental and theoretical study was carried out to estimate the foaming characteristics in the pultrusion process of phenolic foam composite. For the experimental study, a lab-scale pultrusion apparatus was constructed. Methylene chloride(CH2Cl2) was used as a physical blowing agent, glass fiber roving was used as reinforcement and the polymer used was a resol type phenolic resin. Pultruded products were observed to count bubble size by a SEM(Scanning Electron Microscopy). For the theoretical study, a model for bubble growth in a gradually hardening resin was considered and solved for a few foaming conditions.

• Macromolecular Research
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• v.16 no.5
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• pp.467-472
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• 2008

Rigid polyurethane foams (RPUFs) were fabricated from crude MDI (CMDI) and polypropylene glycols (PPGs) of various isocyanate indices with a physical blowing agent (HFC 365mfc). There was a tendency for the gel time to decrease and the tack-free time to increase with increasing index value. With increasing index value the foam density and compression strength decreased and the glass transition temperature, dimension stability and thermal insulation increased, while the cell size and closed cell content were virtually unchanged. Allophanate crosslinks and condensation reactions between the isocyanate groups, which are favored with a high index value, exerted significant effects on the properties of RPUFs.