• Polymer(Korea)
• /
• v.24 no.1
• /
• pp.72-81
• /
• 2000

Benzoic acid polyester/lactone polyol were synthesized by polycaprolactone 0201 as diol, trimethylolpropane as triol, adipic acid as dibasic acid, and benzoic acid as monobasic acid. Polyisocyanate prepolymer Desmodur N-100 of HDI-biuret type was used in this study. Two-component polyurethane coatings were prepared by blending benzoic acid polyester/polycaprolactone, polyisocyanate, wetting/dispersing agent, white pigment, and flowing agent. Various properties were examined on the film coated with the prepared polyurethane. They showed excellent physical properties such as abrasion resistance, accelerated weathering resistance, and yellowness index. They also showed good physical properties such as flexibility, impact resistance, 60$^{\circ}$ specular gloss, cross hatch adhesion, hydrocarbon resistance, and lightness index difference. Hardness of coating showed a little poor character. The introduction of polycaprolactone 0201 as diol in the polyurethane coatings improved the hydrocarbon resistance, impact resistance, and flexibility of coatings. According to the drying and curing behavior with the contents of benzoic acid, they seem to have reasonable coating properties such as drying time of 2 to 4 hours and pot-life time of 20 to 37 hours.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.9
• /
• pp.1729-1733
• /
• 2007

In this paper, we have carried out some tests for analyzing the effects of optical fiber characteristics and piping structures in designing a Customer Cabling System with optical fibers. In this tests, the loss characteristics due to the number of curvatures and the radius of curvature with bending to establish an optical fiber have analyzed particularly. We can confirm that the test results satisfy the current technical regulations in both cases of the number of curvatures and the radius of curvatures. Also, in particular, since there is no loss in an optical cable under the current radius of curvature, that is 30mm, the radius criteria of curvature needs to be revised. These tests results will be so useful to revise and establish a customer cabling system for FTTH.

• Resources Recycling
• /
• v.33 no.1
• /
• pp.48-57
• /
• 2024

This study aimed to improve utilization of the Class C vinyl waste generated in rural areas based on a preliminary investigation on the use of eco-powder, generated through pyrolysis, as a raw material for plastic. The efficiency of pre-processing treatments in controlling ash content of the generated eco-powder and its effect on the basic properties of manufactured plastic were evaluated. The basic properties included ash content of the compressed eco-powder at different levels of ash content, impact strength, flexural strength, and tensile strength. The experimental results confirmed that pre-processing improved the separation efficiency of soil particles and vinyl waste through physical impact. The eco-powder with ash content of less than or equal to 26% was found to satisfy the target performance during impact strength, flexural strength, and tensile strength evaluation. Thus, it was confirmed that the Class C vinyl waste, having low utilization and recovery rates, could be effectively utilized as a plastic raw material after optimum thermal treatment and physical processing using the eco-powder.

• Resources Recycling
• /
• v.17 no.3
• /
• pp.10-20
• /
• 2008

In order to study the behaviors of inorganic fillers in recycling of the waste agricultural plastic films, the washed PE fluffs from Shihwa and Jungeup Plant belonging to ENVICO were used respectively. First of all, the test pellets were manufactured by adding of inorganic fillers suchlike calcium carbonate and calpet by certain portions to PE fluffs and then the tested sheets were formed. The mechanical and thermal properties of the samples were measured and compared with others. The items measured were tensile, flexural, Izod impact, HDT, MFT, and so on. Morphologies were also investigated for various samples using the SEM. Finally, optimum ratios between recycled PE and inorganic additives were found out for the best products in physical condition as well as in economic point of view.

• Tunnel and Underground Space
• /
• v.22 no.2
• /
• pp.77-85
• /
• 2012

In a material, micro-cracks can be progressively occurred, propagated and finally lead to failure when it is subjected to cyclic or periodic loading less than its ultimate strength. This phenomenon, fatigue, is usually considered in a metal, alloy and structures under repeated loading conditions. In underground structures, a static creep behavior rather than a dynamic fatigue behavior is mostly considered. However, when compressed air is stored in a rock cavern, an inner pressure is periodically changed due to repeated in- and-out process of compressed air. Therefore mechanical properties of surrounding rock mass and an inner lining system under cyclic loading/unloading conditions should be investigated. In this study, considering an underground lined rock cavern for compressed air energy storage (CAES), the mechanical properties of a lining system, that is, concrete lining and plug under periodic loading/unloading conditions were characterized through cyclic bending tests and shear tests. From these tests, the stability of the plug was evaluated and the S-N line of the concrete lining was obtained.

• Applied Chemistry for Engineering
• /
• v.26 no.5
• /
• pp.615-620
• /
• 2015

Polypropylene (PP)/bamboo fiber (BF) composites were fabricated by twin screw extruder in order to investigate effects of the compatibilizer on physical properties of PP/BF composites. The content of BF changed from 10 to 25 wt% and that of the compatibilizer was fixed at 3 wt%. Maleic anhydride grafted PP (PP-g-MAH) was used to increase the compatibility between PP and BF as a compatibilizer. Chemical structures of the composites were confirmed by the existence of carbonyl group (C=O) stretching peak at $1,700cm^{-1}$ in FT-IR spectrum. Considering the degradation and mechanical properties, the optimum extrusion conditions were selected to be $210^{\circ}C$ and 100 rpm, respectively. There was no distinct changes in melting temperature of the composites, but the crystallization temperature increased by $10-20^{\circ}C$ owing to the heterogeneous nuclei of BF. It was checked that the optimum BF content was in the range of 15-20 wt% from the results of tensile and flexural properties of the composites. The effect of the compatibilizer on mechanical properties was confirmed by SEM images of fractured surface and contact angles.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.25 no.4
• /
• pp.437-444
• /
• 2009

The purpose of this study was to evaluate the physical properties of different automixing resin cements and the shear bond strength on dentin. For this study, two self-adhesive automixing resin cement(Rely-X Unicem(3M ESPE, St. Paul, USA), Embrace resin cement(Pulpdent, Oakland, USA)) and one chemical polymerizing resin cement(Resiment Ready-Mix(J.L.Blosser Inc., Liberty Missouri, USA)) were used. To evaluate the physical properties, compressive strength, diametral tensile strength and flexural strength were measured. The specimens were fabricated using Teflon mould according to manufacturers' instructions and stored for 24 hours in an atmosphere of 100% humidity. To evaluate the shear bond strength on dentin, each cements were adhered to buccal dentinal surface of extracted human lower molars in 2mm diameter. Physical properties and shear bond strengths were measured using universal testing machine(Z010, Zwick GmbH, Ulm, Germany) at a crosshead speed of 0.5mm/min. The physical properties and shear bond strength of different automixing resin cements were statistically analyzed and compared between groups using One-way ANOVA test and Schffe post-hoc test at the 95% level of confidence. The result shows that chemical polymerizing automixing resin cement represents the relatively higher physical properties and shear bond strength than self-adhesive automixing resin cements.

• Journal of dental hygiene science
• /
• v.9 no.4
• /
• pp.405-412
• /
• 2009

The purpose of this study investigated the effect of Au coating on adhesion between porcelain matrix and metal substructure interface. Titanium, Ni-Cr alloy and Co-Cr alloy are well known as proper metal for the dental restorations. The success of a porcelain fused to metal (PFM) restoration depends upon the quality of the porcelain-metal bond. However, adhesion between dental alloys and porcelain is related to diffusion of oxygen during ceramic firing. The excessive oxidized layers make hard adhesion between dental alloy and ceramic. Ni-Cr and Co-Cr specimens were divided into test and a control group and Titanium specimens were divided into three test groups and a control group. Each group had 20 specimens. The adhesion characteristics of porcelain and metal with Au coating layer and without Au coating layer were observed with scanning electron microscopy(SEM). The adhesion was evaluated by a biaxial flexure test and volume fraction of adherent porcelain was determined by SEM/EDS analysis. Result of this study suggest that Au coating layer is effective barrier to diffuse oxide layer completely protect non-precious alloys from oxidation during the porcelain firing. The SEM photomicrographs of cross-section specimens showed a smooth interface between Au coating layer and metals and porcelain which suggested proper chemical bonding, and no gap, porosity were observed. The mode of failure was mainly adhesive for Ti tested specimens, but mixed failures with adhesive and cohesive were observed in Ni-Cr and Co-Cr specimens. The adhesion between non-precious metals and porcelain would not be improved by Au coating agent. However, It is suggested that the continuous study is required further investigation and development.

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

• Composites Research
• /
• v.32 no.3
• /
• pp.148-157
• /
• 2019

In this study, $C_f/SiC$, $SiC_f/SiC$ and $C_f-SiC_f/SiC$ ceramic composites reinforcing carbon fiber, SiC fiber and hybrid fiber were fabricated by hybrid TGCVI and PIP process. After the thermal shock cycle, 3-point bending and Oxy-Acetylene torch test, their mechanical behavior, oxidation and erosion resistance were evaluated. The $C_f/SiC$ composite showed a decrease in mechanical property along with increasing temperature, a pseudo-ductile fracture mode and a large quantity of erosion. The $SiC_f/SiC$ composite exhibited stronger mechanical property and lower erosion rate compared to the $C_f/SiC$, but brittle fracture mode. On the other hand, hybrid type of $C_f-SiC_f/SiC$ composite gave the best mechanical property, more ductile failure mode than the $SiC_f/SiC$, and lower erosion rate than the $C_f/SiC$. During the Oxy-Acetylene torch test, the $SiO_2$ formed by reaction of the SiC matrix with oxygen prevented further oxidation or erosion of the fibers for $C_f-SiC_f/SiC$ and $SiC_f/SiC$ composites particularly. In conclusion, if a hybrid composite with low porosity is prepared, this material is expected to have high applicability as a high temperature thermo-structural composite under high temperature oxidation atmosphere by improving low mechanical property due to the oxidation of $C_f/SiC$ and brittle fracture mode of $SiC_f/SiC$ composite.