• Clean Technology
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• v.12 no.1
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• pp.11-18
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• 2006

In this study, aqueous polyurethane dispersion(PUD) was synthesized using polyhexamethylene carbonate glycol (PHMCG) as soft segment, isophorone diisocyanate (IPDI) and dimethylol propionic acid (DMPA) as hard segment. Also, polyurethane/clay nanocomposites were prepared by adding pristine montmorillonite (PM) and organically modified clays, C15A and C30B into PUD. The degree of clay dispersion in the nanocomposites was investigated using XRD and the physical and thermal properties were examined through UTM and TGA. These results showed that nanocomposites with C15A gave higher physical and thermal properties than those with C30B or PM. As a result, the properties of nanocomposites were observed to vary depending on the types of clay modifiers and clay contents.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.1
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• pp.1-7
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• 2015

Purpose: For optimizing properties of final glasses frame, the aim of this study is to examine the correlation of processing conditions and properties of cellulose acetate (CA) sheets through the investigation of properties of CA sheets prepared under processing steps. Methods: The properties of CA sheets were investigated in terms of different glasses frame processing conditions, bending process, barrel process, and ultrasonic cleaning process. CA sheets prepared through the sequential processing were examined by various analysis: gloss, mechanical properties, thermal properties. Results: After barrel process, hardness and tensile strength of CA sheet were increased. However, bending strength and impact strength were decreased. It is suggested the CA sheet had became rather stiff state (brittle). Also, in degradation temperature region of plasticizer, about 3% of reduction in plasticizer weight was confirmed upon TGA analysis. Conclusions: Glasses frame process, especially in the barrel process have a profound influence on the properties of CA sheet owing to reduction of total amount of plasticizer.

• Polymer(Korea)
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• v.26 no.1
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• pp.139-144
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• 2002

In this study, the PPS/ABS blend system was investigated in order to identify the relationship between the incorporation of compatabilizing moieties and the mechanical properties. ABS resin was chemically modified by the incorporation of maleic anhydride using reactive extrusion method to yield MABS resin, and PPS/MABS blend was prepared by a twin screw extruder. Single glass transition behavior was observed in the various compositions of PPS/MABS blend by dynamic mechanical analysis study. Upon the examination of the mechanical properties, the PPS/MABS blend exhibited an enhanced tensile, flexural and impact strength, which might be due to the better chemical compatibilization to result in the reduced interfacial tension between each components.

• Journal of Adhesion and Interface
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• v.16 no.2
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• pp.63-68
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• 2015

We synthesized thermoplastic polyurethane elastomer containing carboxylic acid group and TPV (thermoplastic vulcanizate). We measured the mechanical, grip, debris, contact angle and adhesion properties according to introducing acid group in elastomer structure. Mechanical and wet slip properties were improved because of the hydrogen bonding by introduction of acid group. Also adhesion strength was increased as increasing of surface polarity by carboxylic acid group. The debris property of TPV made from TPU containing carboxylic acid group was improved.

• Elastomers and Composites
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• v.36 no.2
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• pp.86-93
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• 2001

For solving the environmental problem of the waste EPDM and for new TPE blend materials, we developed a new kind of TPE material using a co-rotating twin screw extruder. To improve the mechanical properties of TPE material such as tensile strength, elongation at break, and modulus of the blend, PP and waste EPDM powder were blended with different screw configurations. The mechanical properties of the blends and morphology of the TPE were investigated. As the number of kneading disc and left-handed screw element increased, dynamic vulcanization of the material was increased because the shear stress and residence time of blends increased.

• Elastomers and Composites
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• v.41 no.3
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• pp.157-163
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• 2006

In this study, the wettability and mechanical properties of silicone rubber impression material were studied by using precipitated silica and fumed silica with different particle size and polarity (hydrophilic/hydrophobic). Curing time of impression material depended on the particle size of fumed silica. The curing time delayed about 9 minutes by using A300, which was the fumed silica with the smallest particle size among the silica used in this study. Wettability of rubber impression material improved with the introduction oi hydrophobic fumed silica(R972). Also, the optimum flow and mechanical properties could be obtained by using blended silica with the 90: 10 ratio of precipitated and fumed silica.

• Current Research on Agriculture and Life Sciences
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• v.31 no.3
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• pp.177-181
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• 2013

This study examined the effect of the molecular weight, substitution degree, and substitution type of cellulose ether on the mechanical properties of dried rice noodles. When increasing the molecular weight of the hydroxypropyl methylcellulose (HPMC), the bending strength of the dried rice noodles also increased. However, the bending strength of the rice noodles with added HPMCs was still lower than that of the wheat noodles. Meanwhile, the bending elongation of the dried rice noodles was higher than that of the wheat noodles and was increased when decreasing the molecular weight of the HPMC. In conclusion, the bending strength and elongation of dried rice noodles is affected by the substitution degree and type of cellulose ether.

• Composites Research
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• v.26 no.5
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• pp.315-321
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• 2013

In this work, pitch-carbonized glass fibers were prepared for reinforcement of composites. The influence of acid functionalization of the fibers on the morphological, mechanical, and thermal properties of fiber-reinforced epoxy matrix composites was investigated. The acid functionalization of the fibers led to 10 and 150% increases in the mechanical and thermal properties, respectively, as compared to carbon fiber-reinforced composites. This can be attributed to the superior orientation of fiber structures and good interfacial interactions between fillers and epoxy matrix, resulting in enhanced degree of dispersion and formation of thermally conductive paths in the functionalized composites.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.325-329
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• 2023

높은 주조 품질을 요구받고 있는 대부분의 다이캐스팅업체들은 양산공정을 통해 사용되고있는 용탕의 청정도를 평가하고 모니터링을 해야만 한다. 여러 가지 평가방법들을 사용할 수 있지만 현장에서는 일부 측정방법만이 다이캐스팅에 적용되고 있으며 목적에 맞게 적절하게 사용하여야 한다. 세 가지 가능한 평가 방법인 K-Mold, 기계적물성 평가 및 PoDFA(다공성 디스크 여과 장치) 를 대상으로 소개하고자 한다. 우선, 각 방법들은 서로 사용 목적 목적에 따라 선택될 수 있으며 K-Mold는 현장에서 빠르고 간단하게 적용할 수 있는 방법으로 일정한 규격화된 시편의 파면을 만들고 파단면 관찰을 통해 일정한 크기 이상의 산화물 갯수를 확인하여 용탕의 품질을 관리하는 편리한 평가방법 중 하나다. 기계적 물성 테스트는 용탕 청결도에 대한 정성적, 정량적 정보를 모두 확인할 수 있으며 샘플링 테스트에 적합한 시험법이라 할 수 있다. 또한, PoDFA는 용탕내에 개재물의 종류별 정밀분석과 양에 대한 상대적 비교 분석으로써 현장의 많은 경험을 통하여 데이터 축적하고 분석하는 방법으로 사용방법에 대한 전문교육이 필요하다.

• Composites Research
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• v.26 no.4
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• pp.254-258
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• 2013

Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of $750m^2/g$ showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.