• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2958-2965
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• 2015

The PLGA(Poly lactide-co-glycolide) Copolymer have been actively applied to the medical implant material as biomaterials. PLGA membrane was able to alveoloplasty with osteotomy for favorable degradation characteristics and possibilities for sustained drug delivery. In this study, PLGA membrane was prepared using phase inversion method, and examined to optical method analysis(NMR, IR), mechanical property measurement (tearing strength) and thermal characteristic analysis(DSC). In addition, the biodegradation characteristics of the PLGA membrane filled with a PBS(Phosphate Buffered Solution) of the water bath ($60^{\circ}C$) according to the degree of surface degradation in the degradation time, the pH change of the solution and change of the mass of the membrane were measured.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.8
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• pp.1315-1322
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• 1997

Ramie is one of the traditional fabrics in Korea, and very comfortable fabric for summer clothes because it has a high moisture-absorbing and transporting property. Futhermore ramie is very popular and Koreans prefer its handle for summer clothes. The kansan ramie has better quality as fibers and can be weaved as fine fabrics which are famous as kansan Fine ramie. Even though the good quality of kansan ramie has known widely, very few research work have been carried out on kansan ramie in the field of textile science. In this study, the analysis of the physical and chemical characteristics of Hansan ramie was conducted by using two different kinds of Hansan ramie: Hansan Fine ramie and kansan Coarse ramie. In addition, the same experiment was held on the one kind of chinese ramie to be compared with those of Hansan ramie. The following results were obtained from this experimental study. By the analysis of chemical composition of ramie, the similar chemical composition (a -cellulose: 83∼85%, pectin substances: 2.81∼ 3.01%) were found from all of the ramie fabrics used in this study. It has shown that Hansan coarse ramie has the highest toughness value and wrinkle recovery angle among the samples used in this study. From the result of KES-F system, it was found that Hansan Coarse ramie which is composed with the thicker yarns has the highest value on the bending properties, 2HG and surface properties. The primary hand value was also calculated by KN-203 LDY and value of Koshi was shown as the order of kansan coarse ramie> Chinese ramie> kansan fine ramie, and Hansan fine ramie had shown the highest Numeri and Fukurami value among the 3 samples used in this study.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.167-172
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• 2012

A new type of thermoplastic elastomer (TPE) based on EPDM ionomer as an elastomer and polyamide-6 as a reinforcing crystalline polymer was prepared and the thermal properties of TPEs were investigated. Especially effects of neutralization of maleated EPDM (MA-EPDM) to prepare EPDM ionomer with zinc oxide and the content of polyamide-6 on the thermal properties of the blends were investigated. Both the neutralization and blending were carried out employing a twin screw extruder. It was found that the neutralization of MA-EPDM results in the increase of cooling crystallization temperatures. Polyamide-6 plays the role of reinforcing filler in the blends due to the high crystallinity. Fine dispesion of polyamide-6 in the blends was confirmed and attributed to the imide formation between the maleic anhydride of MA-EPDM and amine group of polyamide-6. TPEs based on EPDM ionomer/Polyamide-6 blends showed balanced mechanical properties with improvement in heat resistance.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.12-18
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• 2017

Transparent organic-inorganic hybrid hard coating films were prepared by the addition of $SiO_2$ or $ZrO_2$, as an inorganic filler to improve the hardness property, filler was highly dispersed in the acrylic resin. To improve the compatibility in the acrylic resin, $SiO_2$ or $ZrO_2$ is surface-modified using various silanes with variation of the modification time and silane content. Depending on the content and kind of the modified inorganic oxide, transparent modified inorganic sols were formulated in acryl resin. Then, the sols were bar coated and cured on PET films to investigate the optical and mechanical properties. The optimized film, which has a modified $ZrO_2$ content of 4 wt% markedly improved in terms of the hardness, haze, and transparency as compared to neat acrylate resin and acrylate resin containing modified $SiO_2$ content of 8 wt%. Meanwhile, the low transparency and high haze of these films slowly appeared at $SiO_2$ content above 10 wt% and $ZrO_2$ content of 5 wt%, but the hardness values were maintained at 2H and 3H, respectively, in comparison with the HB of neat acrylate resin.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.918-927
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• 2018

Based on the actual operating environment of transformer, the aging tests of nitrile butadiene rubber (NBR) were conducted systematically under four conditions: in air, in transform oil, under compression in air and under compression in transform oil to studythe effect of high temperature, transform oil and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber and predict the lifetime. The effects of liquid media and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber were studied by using characterization methods such as IR spectrosc-opy, thermogravimetric measurements, Differential Scanning Calorimetry (DSC) measurements and mechanical property measurements. The changes in physical properties during the aging process were analyzed and compared. Different aging conditions yielded materials with different properties. Aging at $70^{\circ}C$ under compression stress in oil, the change in elongation at break was lower than that aging in oil, but larger than that aging under compression in air. The compression set or elongation at break as evaluation indexes, 50% as critical value, the lifetime of NBR at $25^{\circ}C$ was predicted and compared. When aging under compression in oil, the prediction lifetime was lower than in air and under compression in air, and in oil. It was clear that when predicting the service lifetime of NBR in oil sealing application, compression and media liquid should be involved simultaneously. Under compression in oil, compression set as the evaluation index, the prediction lifetime of NBR was shorter than that of elongation at break as the evaluation index. For the life prediction of NBR, we should take into account of the performance trends of NBR under actual operating conditions to select the appropriate evaluation index.

• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.177-183
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• 2015

In this study, the thermal conductivity, physical and mechanical properties of lightweight aggregate concretes with hollow micro sphere(HMS) are experimentally examined as a basic research for the development of structural insulation concrete. As the results of this experiment, in the case of concrete mixed with HMS, the value of slump has been reduced, so it is found that the dosage of superplasticizer should be increased. As the replacement ratio of HMS increases, it has shown that the compressive strength is somewhat decreased due to the low interfacial adhesion strength of HMS. But the thermal conductivity is found to be greatly improved with the replacement ratio of HMS increases, the thermal conductivity of HMS shows the lower value of 68% at lightweight aggregate concrete and 32% of normal concrete. Also it is found that the compressive strength is decreased and thermal conductivity is increased as the water-cement ratio increases. The most outstanding for insulation performance is observed when using 20% of HMS and 50% of water-cement ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.849-855
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• 2017

The development of a staged combustion cycle engine with higher perfomance is essential to provide higher transport capability of space launch vehicles. The combustor head of engine has a cone-shaped head and its manifold of combustor has a very complicated structure. The head and manifold have been manufactured by casting or machining methode. Metal 3D printing technologies are recently known as one of promising methods to improve manufacturing process for them because they are possible to over come limitations of the two methods. In this paper, a selective laser sintering method is used to make test materials and their physical properties are studying by changing its operation parameters to establish the better processing conditions. It is found that the 3D printing method is acceptable to manufacturing the head or manifold of combustor for staged combustion cycle engine.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.6
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• pp.750-756
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• 2009

Cherry powder (obtained from ground fruit of Prunus serrulata L. var. spontanea Max. wils.), which is a natural functional material, was used in muffin manufacturing at different concentrations from 0, 3, 5, 7, and 10% (w/w). Muffin was evaluated for their sensory property and physical quality. The antioxidative activity measured by DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity of muffin increased as the concentrations of cherry powder increased. As the concentration of cherry powder increased, the mechanical characteristics of the muffin, such as hardness increased, but gumminess and chewiness decreased. Lightness (L) and yellowness (b) of muffin decreased as the concentration of cherry powder increased, whereas the redness (a) increased. The muffins containing 3, 5, 7, and 10% cherry powder had acceptable sensory properties, such as color, flavor, taste, softness, moisture, and overall acceptability. The results exhibited that adding the cherry powder into the muffin increased antioxidant activity. The highest quality improvement was obtained by incorporating 5% (w/w) of cherry powder into the muffin formula.

• Journal of Fashion Business
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• v.14 no.6
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• pp.39-52
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• 2010

Interests in creating three-dimensionally designed fabric materials are growing rapidly in the sectors of the fashionable textiles with the creativity, new functions, and aesthetics. A number of finishing methods have been developed and proposed to add or create new functions and designs for silk fabrics. Due to the strong hydrogen bonds between the molecules of silk fibroins, the thermal treatment methods used in thermoplastic fiber processing, which can easily deform the synthetic filament fabrics to endow three-dimensional appearance to the fabrics, are not applicable to the silk fabric treatment. In order to modify the fine structure of silk fiber, neutral salt solution treatment methods have been suggested. In this study, the effect of the calcium nitrate solution on the physical and mechanical properties of silk fabrics was investigated by using the KES(Kawabata Evaluation System) equipment. Based on these findings, relationships between parameters, for example, the thickness and the compressional energy, the thickness and the compressional linearity, and the air permeability and the pore area statistical analysis were investigated. The relationships between the process parameters such as treatment temperature/time and the resulting fabric property parameters were also analyzed by using several SAS procedures.

• Elastomers and Composites
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• v.49 no.2
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• pp.127-133
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• 2014

Rubber composites were prepared by kneading the precured CIIR with BR in order to analyze the effects of the dispersed phase on the BR/PCIIR composites. The particle size of domain in BR/CIIR composites was decreased and homogeneously dispersed by kneading process the precured CIIR used as dispersed phase in kneader once again. In case of BR/PCIIR40, the kneading time of precured CIIR with BR did not have any effect on the rebound resilience and the hardness of the composite. The tensile strength of the composite prepared by kneading precured CIIR particles and then mixing them with BR increased significantly more than 10% when compared to that of the composite which was not kneaded. The composite maintained the surface friction property while increasing anti-abrasion and mechanical properties significantly by kneading the precured CIIR used as dispersed phase.