• Polymer(Korea)
• /
• v.27 no.4
• /
• pp.340-348
• /
• 2003

A previous stud-pull test was modified to measure the bond strength of polyurethane foam to carbon steel substrate. This test was appropriate in that the specimen foamed on Zn phosphated steel (0.95 kN) was broken at higher load than that of smooth galvanizing treated steel (0.38 kN). Among the samples foamed on the substrate atvarious preheating temperatures, the polyurethane foam to the steel held over 60$^{\circ}C$ exhibited very high bond strength. The samples were exposed at water vapor absorption, and, then, their bond strengths were measured. The adhesion was significantly reduced in the samples foamed on the steel at temperatures below 40$^{\circ}C$ and above 70$^{\circ}C$. For the polyurethane foams formulated with two blowing gases, the adhesion was higher by 0.03 kN in the samples with HCFC-l4lb than that with HFC-245fa. When the these samples were exposed at water vapor soaking, the reduction of the bond strength for the HFC-245fa blown sample was negligible due to smaller area fraction of void area filled with gas at interfacial area. Consequently, it was found that adhesion of polyurethane foam to metal substrate was determined by variation of microstructural features with substrate preheating, surface treatment type of blowing agent.

• Journal of the Korean Society of Safety
• /
• v.33 no.2
• /
• pp.8-13
• /
• 2018

The light weight composite materials have been replacing in high performance structures. The object of this study is to examine the effects of the initial crack location about a delamination in a PVC foam cored sandwich composite that is used for the strength improvement of structures. The initial crack location and fiber laminates thickness were changed with several types. The MMB specimen was used for evaluating the fracture toughness and crack behaviors. The material used in the experiment is a commercial twill carbon prepreg in CFRP material and Airex in PVC foam core. Sandwich laminate composites are composed by PVC foam core layer between CFRP face sheets. The face sheets were fabricated as 2 types of 5 and 8 plies. The initial cracks were located in a PVC form core and the interface of upper CFRP sheet. From the results, the crack initiation was affected with the location of the initial crack inserted in the PVC foam core. Among them, the initial crack at 1/3 of the upper part of the PVC foam core was the most rapid progression. And the critical energy release rate was $0.40kJ/m^2$, which is the lowest value when the initial crack was inserted into the interface between a PVC foam core and CFRP laminated with 5 plies. Meanwhile, the highest value of $1.27kJ/m^2$ was obtained when the initial crack was located at the center line in case of the 8 plies.

• International Journal of Precision Engineering and Manufacturing
• /
• v.2 no.3
• /
• pp.47-53
• /
• 2001

This paper investigates the characteristics of interlaminar fracture toughness of foam core sandwich structures under opening mode by using the double cantilever beam (DCB) specimens which are Carbon/Epoxy and foam core composites. Instead of using a DCB specimen of symmetric geometry, a non-symmetric DCB specimen was used to calculate the interlaminar fracture toughness. Three approaches for calculating the energy release rate(G$\sub$IC/) were used and fracture toughness of foam core sandwich structures made by autoclave, vacuum bagging and hotpress were compared. Experiment, analysis using nonlinear beam bending theory, and numerical work by FEM methods were performed. Bonding surface compensation and equivalent moment of inertia were used to calculate the energy release rate in nonlinear analytical work. Conclusions of experimental, nonlinear analytical and FEM methods were compared. It is, also, shown that the vacuum bagging forming can substitute the method of autoclave without serious loss of Mode I energy release rate(G$\sub$I/).

• Journal of the Korean Chemical Society
• /
• v.29 no.6
• /
• pp.656-663
• /
• 1985

A catalytic conversion of carbon monoxide has been studied in a coal combustion system. Three different catalysts were prepared by impregnating 0.2% platinum on three different types of supports, ${\gamma}-Al_2O_3$ pellets, ceramic foam and honeycomb. These catalysts have shown an excellent initial activities in the coal combustion system, but they were rapidly deactivated in repeated uses. Among these catalysts ceramic foam has shown to be better than others both in activities and durabilities. The main cause of deactivation seems to be ascribed to poisoning by zinc metal and sulfur compounds and to decrease in platinum surface area by sintering.

• Journal of the Korea Concrete Institute
• /
• v.24 no.1
• /
• pp.61-70
• /
• 2012

Recently, the government has been working feverously to save energy and reduce greenhouse gas emission by enacting Basic Act on Low Carbon Green Growth at the national level. Improving the insulation performance of building exterior and insulator can reduce the energy in the building sector. This study is about developing light-weight foamed concrete insulation panel that can be applied to buildings to save energy and to find the optimal condition for the development of insulation materials that can save energy by enhancing its physical, kinetic and thermal characteristics. Various experimental factors and conditions were considered in the study such as foam agent types (AES=Alcohol Ethoxy Sulfate, AOS=Alpha-Olefin Sulfonate, VS=Vegetable Soap, FP=Fe-Protein), foam agent dilution concentration (1, 3, 5%), and foam percentage (30, 50, 70%). Experiment results indicated that the surface tension of aqueous solution including foam agent, was lower when AOS was used over other foam agents. FP produced relatively stable foams in 3% or more, which produced unstable foams containing high water content and low surface tension when diluted at low concentration. Depending on foam agent types, compressive strength and thermal conductivity were similar at low density range but showed some differences at high concentration range. In addition, when concentrations of foam agent and foaming ratio increased, pore size increased and open pores are formed. In all types of foam agent, thermal conductivity were excellent, satisfying KS standards. The most outstanding performance for insulation panel was obtained when FP 3% was used.

• Carbon letters
• /
• v.18
• /
• pp.11-17
• /
• 2016

Monolithic carbon foams with hierarchical porosity were prepared from polyurethane templates and resol precursors. Mesoporosity was achieved through the use of soft templating with surfactant Pluronic F127, and macroporosity from the polyurethane foams was retained. Conditions to obtain high porosity materials were optimized. The best materials have high specific surface areas (380 and 582 m² g^-1, respectively) and high electrical conductivity, which make them good candidates for supports in sensors. These materials showed an almost linear dependence between the potential and the pH of aqueous solutions.

• Composites Research
• /
• v.37 no.2
• /
• pp.86-93
• /
• 2024

The inner foam structure plays an important role in the performance of the carbon-fiber-reinforced plastic (CFRP) rear spoiler used in automobiles. However, there is still a lack of studies for the CFRP-based rear spoiler according to the type of inner foam, especially under the high-speed driving condition. With this motivation, we numerically analyze the performance of the CFRP rear spoiler using various cases of the inner foam under the highspeed driving condition. Here, polymethacrylimide (PMI), polyvinyl chloride (PVC), and styrene acrylonitrile (SAN) resins are employed as the inner foams in this work. The performances are evaluated using the deformation aspects and vibration characteristics when the driving condition is a high-speed condition (200 km/h). Furthermore, to specifically verify the importance of the inner foam in the high-speed condition, we additionally investigate the performance of the CFRP rear spoiler without the inner foam structure (i.e., hollow type). As a result, it is confirmed that among the types of inner foams utilized in this work, the PMI and PVC inner foams have the best deformation aspect and vibration characteristic, respectively. Note that the hollow-type inner foam has inferior performances compared to other inner foams invoked in this study. Consequently, through this study, it can be confirmed that the inner foam structure can significantly improve the performance of the CFRP spoiler under high-speed driving condition (200 km/h), and also that the strengths of the CFRP spoiler can manifest differently depending on the types of inner foam core.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.124.1-124.1
• /
• 2005

• Applied Chemistry for Engineering
• /
• v.33 no.6
• /
• pp.613-617
• /
• 2022

The equipment for fabricating the large-area PTFE nanofiber coated-PTFE foam filter for use as filtration parts of the baghouse that removes particulate matter (PM) in industrial sites was designed and manufactured in this study. The PTFE nanofiber was coated on a commercial PTFE foam filter to increase its PM collection efficiency. The equipment and fabrication processes using a roll-to-roll system were proposed to continuously coat PTFE nanofibers on the surface of the PTFE foam filter. The electrospinning and annealing parts were designed and made by optimizing the equipment for the roll-to-roll system. The surface morphology, composition, and filtration characteristics of the large-area filter fabricated by this equipment were confirmed. PTFE nanofibers were uniformly coated on the large-area filter, and the PTFE nanofiber coated-PTFE foam filter showed PM_2.5 collection efficiency of 91.79% and an appropriate pressure drop of 62 Pa with a face velocity of 1 m/min at 280 ℃.

• Applied Chemistry for Engineering
• /
• v.7 no.5
• /
• pp.813-822
• /
• 1996

In order to reduce carbon dioxide, one of the major greenhouse gases, a new type of copolymer, poly(alkylene carbonate) has been synthesized. The alternating copolymers have been obtained from carbon dioxide and various epoxides with zinc carboxylate as a catalyst. The number-average molecular weight of the polymer is about 50,000 and polydispersity is rather broad(5~10). The polymers are amorphous, and glass-clear materials that exhibit unusually facile and clean thermal decomposition behavior. Complete decomposition with no carbon residue is observed at elevated temperature even in an inert atmosphere. Terpolymers with bulkier epoxides improve the physical properties of the copolymer with simple epoxides. The decomposition properties of the polymer provide versatile applications such as ceramic, metal, and electronic binders and lost-foam casting. Further application of the polymer for the barrier film or the plasticizer will be investigated.