• Polymer(Korea)
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• v.26 no.1
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• pp.113-120
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• 2002

Electrostriction is the phenomenon that a material is strained due to Maxwell stress developed by the applied voltage. In many electrostrictive materials, especially polymeric elastomers can produce large deformation and force due to their low elastic modulus. In this study, polyurethanes and acrylic rubber with compliant electrodes were used as electrostrictive polymer(EP) actuator. Actuation characteristics of the EP actuators with different physical properties of dynamic modulus and dynamic dielectiric constant were analyzed under AC field. The classical laminate theory was also used to simulate the actuation process in relation to the geometry and the physical properties of the actuators.

• Elastomers and Composites
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• v.38 no.4
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• pp.342-353
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• 2003

This work is about the development of jet-fuel resistant PVC sealant using a polyester plasticizer. PVC copolymer was compounded with adipic acid glycol(Songcizer P-3000) or DOP plasticizers. Fuel-immersed and non-immersed penetration, solubility, flow, and elongation by tensile adhesion of PVC compounds were measured. Penetration increase by fuel immersion and solubility of PVC compounds with adipic acid glycol polyester plasticizer were smaller than those of PVC compounds with DOP plasticizer. Elongation by tensile adhesion test of PVC compound containing 500 phr of Songcizer P-3000 decreased proportionally to the content of DCDP (dicyclopentadiene) base petroleum resin adhesion promoter. Calcium carbonate($CaCO_3$) filler inhibited the diffusion of fuel in all the PVC compounds and decreased the solubility of PVC compounds containing Songcizer P-3000.

• Elastomers and Composites
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• v.43 no.2
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• pp.82-87
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• 2008

In this study, nine kinds of polyimides were synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA), m-pheny lenediamine (m-PDA) and 4,4'-oxydianiline (ODA) by controlling molar ratio of monomers. Synthesized polyimides were used as insulator films for 2-layer Flexible Copper Clad Laminate(FCCL) which were manufactured by the casting method. Glass transition temperature and thermal degradation temperature for 5% weight loss of the polyimide film were improved by increasing contents of m-PDA and PMDA, respectively. Water absorption of polyimide film was reduced by increasing contents of ODA and BPADA which have relatively long structure, respectively. Peel strength of 2-layer FCCL was improved by increasing contents of ODA and BPADA.

• Elastomers and Composites
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• v.48 no.2
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• pp.125-132
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• 2013

In this work, we have discussed new engineering systems for preparing carbon master batch composed by carbon black and various organic compounds. In general, polymer resin, which applied for automobile tire, household items, and various industry items, is used with the fillers including carbon black and silica to control the color or properties. Domestic part and material industry has been remarkably developed in that the development of materials including the compounding of raw materials. Meanwhile, the engineering technique for mass production has not reached to a requirement of industry due to slow technique development and high dependence on foreign. Thus, we will focus on the introduction of new engineering technique developed by domestic company for preparing carbon master batch.

• The Research Journal of the Costume Culture
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• v.25 no.3
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• pp.270-284
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• 2017

This study aimed to create 3D-printed insoles for flat-footed senior men using 3D systems. 3D systems are product-manufacturing systems that use 3-dimensional technologies like 3D scanning, 3D modeling, and 3D printing. This study used a 3D scanner (NexScan2), 3D CAD programs including Rapidform, AutoCAD, SolidWorks, Nauta+ compiling program, and a 3D printer. In order to create insoles for flat-footed senior men, we analyzed horizontal sections of 3D foot scans We selected 20 flat-footed and 20 normal-footed subjects. To make the 3D insole models, we sliced nine lines on the surface of the subjects' 3D foot scans, and plotted 144 points on the lines. We calculated the average of these 3D coordinates, then located this average within the 3D space of the AutoCAD program and created 3D sole models using the loft surface tools of the SolidWorks program. The sole models for flat feet differed from those of normal feet in the depth of the arch at the inner sideline and the big toe line. We placed the normal-footed sole model on a flat-footed sole model, and the combination of the two models resulted in the 3D insole for flat feet. We printed the 3D modeled insole using a 3D printer. The 3D printing material was an acrylic resin similar to rubber. This made the insole model flexible and wearable. This study utilized 3D systems to create 3D insoles for flat-footed seniors and this process can be applied to manufacture other items in the fashion industry as well.

• Clean Technology
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• v.5 no.2
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• pp.45-52
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• 1999

Recycling of red mud from the aluminium manufacturing process was investigated to be utilized as plastic fillers. High density polyethylene(HDPE), low density polyethylene(LDPE) and polypropylene(PP) were found to be the suitable plastic material for which red mud can be used as fillers. With the addition of red mud the plastic showed red brown color. As the ratio of amount of red mud to plastic increased, the tensile strength increased while the Izod impact strength decreased. About five percent of ethylene vinyl alcohol(EVA) was needed as an additive to prevent the lowering of impact strength. Maleic anhydride modified polypropylene was effective for reduction of impact strength lowering of PP. Mixed waste plastics containing LDPE, HDPE, PP, polystyrene and ABS could also accommodate red mud as fillers. In this case, significant loss in mechanical properties were observed due to immiscibility between the components. Ethylene propylene rubber(EPR) and styrene butadiene styrene block copolymer (SBS) could be used to improve the impact properties of the commingled waste plastics.

• Elastomers and Composites
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• v.44 no.4
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• pp.373-377
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• 2009

Most of the plastics products are being manufactured by injection molding. Warpage in injection molded affects the product dimension and it causes assembling problem. In this study, warpages in the injection molded part been studied. Specimens are rectangular flat shapes with and without ribs. Amorphous polymers (PC and ABS) and crystalline polymers (PP and PA66) were used for material. Flat shape with ribs showed higher warpage than flat shape without ribs by 6 to 9%. The specimens with ribs that are located parallel to the flow direction has higher warpage than specimens with ribs that are located perpendicular to the flow direction by 25 to 39%. Crystalline polymers have higher warpage than amorphous polymers by 23 to 67%. Warpage decreases as packing time increases and it increases as injection temperature increases.

• Elastomers and Composites
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• v.44 no.4
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• pp.358-365
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• 2009

High-frequency induction is an efficient way to rapidly heat mold surface by electromagnetic induction. In the present work, high-frequency induction heating is applied to injection molding of a mobile phone cover in order to eliminate weldlines by efficiently raising the mold temperature. Through the induction heating experiments, the maximum temperature of $143^{\circ}C$ is obtained on the mold surface in 3s of heating, which is higher than the glass transition temperature of the resin material. An injection molding experiment is then performed with the aid of induction heating, from which we can successfully remove all the weldlines of the mobile phone cover. The effect of induction heating conditions such as the heating power and the heating time on the surface appearance is experimentally investigated.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.1
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• pp.14-24
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• 2001

The purpose of this study was to compare the fracture strengths and the fracture patterns of several hybrid-ceramic crowns and metal-ceramic crown. Ten crowns were constructed for each group according to the manufacturer's instruction. Removable template of silicone rubber impression material was used for standardization of each crowns. Each crown was cemented on a metal die with hybrid glass ionomer cement. All crowns cemented were stored in distilled water, $36^{\circ}C$ for 24 hours prior to loading in an universal testing machine. The load was directed at 130 degrees the long axis of metal die. The fracture strengths were measured and the fracture patterns were observed. The following results were obtained from this study 1. The mean fracture strengths of $Artglass^{(R)}$, $Sculpture^{(R)}$ and $Targis^{(R)}$ were $57.5{\pm}9.5Kgf,\;62.7{\pm}12.2Kgf$ and $60.2{\pm}10.1Kgf$ respectively. There was no significant difference among each hybrid ceramic crown group. 2. The toad required to fracture hybrid-ceramic crowns was significantly smaller than metal-ceramic crowns($131.7{\pm}22.0Kgf$). 3. In the metal-ceramic crowns, labial porcelain detached partially from porcelain-metal junction of proximal side by load. 4. Hybrid-ceramic crowns showed a simple fracture pattern that fracture line began at the loading area and extended through proximal surface, perpendicular to the margin. The crown was separated into two parts of labial side and lingual side. Above results revealed that three kinds of the hybrid-ceramic crowns used in this study must have careful application in clinical use since the strength of hybrid-ceramic crown was lower(about 1/2) than that of metal-ceramic crown.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.115-124
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• 2007

The initial shape is arrived at by a self-formation process, which accomplishes a form in the natural world, or is determined analytically by considering the equilibrium of initial stress only. Therefore, the self-formation process, which accomplishes a form in the natural world is grasped and the types of modeling techniques available to find the shapes of soft structures are well investigated and classified. To establish a form-finding modeling techniques, the models of string, soap film, fabric, rubber, plaster, and etc. are used. These modeling techniques can be used as a method of understanding the characteristics of structures when the material of model shows similar characteristics. Generally, the model test confirms the structure based on numerical analysis, at the same time it is important preceding process to develop such a program. With the above process, the relationship between model test and numerical analysis becomes a feedback process. Therefore, in this study, two examples which have been accomplished from such a technique are investigated and considered according to modeling process.