• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.320-326
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• 2017

This study is based on the hot air welding application method of EVA sheet to test the tensile strength performance changes due to the hot air welding speed, temperature and chemical attack. For the parameters of the study, the hot air welding method that directly heats the overlap between the sheets and the adhesion surface was controlled, and the maximum temperature for application was set to $20^{\circ}C$, $0^{\circ}C$, $-5^{\circ}C$, $-10^{\circ}C$. According to the results of the testing, the tensile strength of the overlap area was the highest between the temperatures of 20 at 5~6m/min and between the low temperatures at 3~4m/min of hot air welding speed.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.168-175
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• 2018

In order to investigate the effect of the chemical treatment of bamboo fiber on physical properties of polypropylene (PP)/bamboo fiber (BF) composites, silane coupling agents such as ${\gamma}$-aminopropyltriethoxysilane (APS), ${\gamma}$-glycidoxypropyl-trimethoxysilane (GPS) and ${\gamma}$-mercaptopropyltrimethoxysilane (MRPS) were applied to BF and alkaline treated BF. Morphological properties of the chemically treated BF were confirmed by optical microscope and SEM measurements, and chemical structure changes were confirmed by FT-IR and EDS. TGA results showed that the thermal stability of silane treated BF increased. Based on the analysis of a universal testing machine and an Izod impact test, the flexural and impact properties of PP/silane treated BF composites showed higher values than those of PP/BF composites. The enhancement of interfacial adhesion properties of the PP/BF composite was checked from SEM images of the fracture of specimens after the tensile test.

• The Journal of Advanced Prosthodontics
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• v.7 no.6
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• pp.484-495
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• 2015

PURPOSE. This study was to evaluate the effects of bacterial cellulose (BC) membranes as a barrier membrane on guided bone regeneration (GBR) in comparison with those of the resorbable collagen membranes. MATERIALS AND METHODS. BC membranes were fabricated using biomimetic technology. Surface properties were analyzed, Mechanical properties were measured, in vitro cell proliferation test were performed with NIH3T3 cells and in vivo study were performed with rat calvarial defect and histomorphometric analysis was done. The Mann-Whitney U test and the Wilcoxon signed rank test was used (${\alpha}<.05$). RESULTS. BC membrane showed significantly higher mechanical properties such as wet tensile strength than collagen membrane and represented a three-dimensional multilayered structure cross-linked by nano-fibers with 60 % porosity. In vitro study, cell adhesion and proliferation were observed on BC membrane. However, morphology of the cells was found to be less differentiated, and the cell proliferation rate was lower than those of the cells on collagen membrane. In vivo study, the grafted BC membrane did not induce inflammatory response, and maintained adequate space for bone regeneration. An amount of new bone formation in defect region loaded with BC membrane was significantly similar to that of collagen membrane application. CONCLUSION. BC membrane has potential to be used as a barrier membrane, and efficacy of the membrane on GBR is comparable to that of collagen membrane.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.3
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• pp.411-436
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• 1992

The purpose of this study was to assess the adhesion of resilient denture liners (such as, heat-cured silicone molloplast B,cold- cured silicone Mollosil) to polymethyl metacrylate (K-33) and metal (Megalloy) in the laboratory by peel test. The resilient denture lines were processed according to manufactures instruction, onto prepared specimens(original resin base plate, rough resin base plate, stippled metal plate, mesh metal plate ) 75mm long and 25m wide. And then, the peel test was performed by instron. The results were as follows : 1. The bonding strength of Mollosil was stronger than that of Molloplast B except the specimen of stippled metal plate. 2. The tensile strength of Mollosil was weaker than that of Molloplast Bas tearing of Mollosil was occured in the peel test. 3. Mesh metal plate had the highest bonding strength in the case of Molloplast B and Mollosil. But stippled metal plate have high bonding strength in the case of Molloplast B and have the lowest bonding strength in the case of Mollosil. 4. The bonding strength of rough resin base plate was stronger than that of original resin base plate in the case of Molloplast B and Mollosil. 5. The bonding strength of metal plates was stronger than that of resin base plates in the case of Molloplast B and Mollosil except the case of bonding strength between the stippled metal plate and Mollosil. 6. It seems that the Increase of surface and retention form of metal plate and resin base plate produces higher physical bonding strength.

• The Journal of Korean Academy of Prosthodontics
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• v.17 no.1
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• Journal of Biomedical Engineering Research
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• v.20 no.1
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• pp.99-106
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• 1999

Ultra-high molecular weight polyethylene (UHMWPE) was crosslinked in the melt state to enhance wear resistance, Dicumyl peroxide (DCP) and triallyl cyanurate (TAC) was used as a crosslinking agent and a promoter, respectively. With increasing amount of DCP and TAC used, gel content of crosslinked UHMWPE (XUMPE) increased, while the melting temperature, crystallizaiton temperature, crystallinity, and tensile properties decreased. The results of pin-on-disk wear test and ball-on-disk test with small applied load showed reduced wear volumes of XUMPE from that of the unmodified UHMWPE. As the wear mechanism effected in the experimental condition of this study was thought to be deformation rather than adhesion or fatigue, a new parameter, the ratio of maximum contact stress to yield stress, was proposed to correlate well with observed wear resistance. In ball-on-disk wear test with larger applied load, XUMPE showed higher wear volumes than that of the unmodified UHMWPE which were accompanied with increased friction coefficients and surface roughness of the wear tracks. When contact stress was well above yield stress, the failure of XUMPE, as well as deformation, was thought to be much accelerated.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.1-8
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• 2014

PURPOSES : The objective of this study is to evaluate the bond strength of asphalt emulsions including polymer-modified emulsions for chip seals and fog seals using the bitumen bond strength (BBS) test. METHODS : For the laboratory testing, the Pneumatic Adhesion tensile Testing Instrument(PATTI) device is used to measure the bond strength between the asphalt emulsion and aggregate substrate based on the AASHTO TP-91. In order to conduct all the tests in controled condition, all test procedures are performed in the environmental chamber. The CRS-2L and the SBS CRS-2P emulsions are used as a polymer-modified emulsion, and then unmodified emulsion, the CRS-2, is compared for the evaluation of chip seal performance. For the fog seal performance evaluation, two types of polymer-modified emulsions and one of unmodified emulsion, the CSS-1H, are employed. For chip seal study, the BBS tests are performed at 30, 60, 120, and 240 minutes of curing times with curing and testing temperatures of $15^{\circ}C$, $25^{\circ}C$, and $35^{\circ}C$. The fog seal tests are conducted at 30, 60, 90, 120, 180 minutes, and 24 hours with curing and testing temperatures of $25^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$. RESULTS AND CONCLUSIONS : Overall, chip seal emulsions and fog seal emulsions show the similar bond strength trend. At the same testing condition, polymer-modified emulsions show better bond strength than unmodified emulsions. Also, there is no significant difference between polymer-modified emulsions. One of important findings is that the most bond strength reaches their final bond strength within one hour of curing time. Therefore, the early curing time plays a vital role in the performance of chip seals and fog seals.

• Elastomers and Composites
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• v.59 no.2
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• pp.73-81
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• 2024

In the field of electronic components, the potting material, which is a part of the electronic circuit package, plays a significant role in protecting circuits from the external environment and reducing signal interference among electronic devices during operation. This significantly affects the reliability of the components. Therefore, the accurate prediction and assessment of the lifespan of a material are of paramount importance in the electronics industry. We conducted an accelerated thermal aging evaluation using the Arrhenius technique on elastic potting material developed in-house, focusing on its insulation, waterproofing, and contraction properties. Through a comprehensive analysis of these properties and their interrelations, we confirmed the primary factors influencing molding material failure, as increased hardness is related to aggregation, adhesion, and post-hardening or thermal-aging-induced contraction. Furthermore, when plotting failure times against temperature, we observed that the hardness, adhesive strength, and water absorption rate were the predominant factors up to 120 ℃. Beyond this temperature, the tensile properties were the primary contributing factors. In contrast, the dielectric constant and loss tangent, which are vital for reducing signal interference in electric devices, exhibited positive changes(decreases) with aging and could be excluded as failure factors. Our findings establish valuable correlations between physical properties and techniques for the accurate prediction of failure time, with broad implications for future product lifespans. This study is particularly advantageous for advancing elastic potting materials to satisfy the stringent requirements of reliable environments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.110-116
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• 2013

A concrete structure has become bigger and higher because of development of construction technology and a change in construction environment. Also it tends to focus on repairing, reinforcement and exterior in harmony with environment for structure maintenance and performance improvement. The research is about eco friendly durable painting applicable to concrete structure using civil and architecture. it purpose to improve external beauties and durable problems due to flexibility by variation of temperature, adhesion of exterior wall, crack and delamination in existing organic and mineral painting. For those problems, we made a eco friendly pre-paint that is made with preliminary treatment mixture as a highly enriched waterproof agent and adhesive increasing agent in preprocessing mixture. Then we performed an experiment on durability of prevention neutralization of concrete, durability abrasion, hiding power, adhesion, temperature resistance and resistance to chemical attack. The result of an experiment shows that hiding power is over 0.96 in standard test, durability abrasion test got higher value 1mg than water paint 75mg and tensile strength is 6 times higher than standard waterproof specification.

• Journal of Adhesion and Interface
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• v.23 no.2
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• pp.44-52
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• 2022

Epoxy resin has the disadvantage of being easily destroyed by instantaneous impact due to its high crosslinking density despite its high glass transition temperature (T_g) and excellent properties. To compensate for this, in this study, polyol was synthesized by ring opening polymerization of propylene glycol (PPG) diamine, Jeffamine D 2000 and propylene carbonate, and urethane modified epoxy was synthesized using this. The properties of the synthesized urethane modified epoxy were confirmed by FT-IR, H-NMR. To confirm the degree of improvement in impact resistance as an adhesive, a urethane modified epoxy adhesive was prepared by mixing a digylcidyl ether bisphenol A (DGEBA) with curing agent and curing accelerator. Properties test of urethane modified epoxy were shear strength, tensile strength and impact strength. As a result, excellent results were obtained in all test when the ratio of DGEBA : urethane modified epoxy was 8:2.