• Elastomers and Composites
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• v.48 no.3
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• pp.232-240
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• 2013

Microcapsules having healing agent were prepared in which 2,6-dimethylphenol (DMP) as a healing agent forms the core and melamine/formaldehyde resin forms the shell. Microcapsule-contained asphalts showed better mechanical properties than non-contained ones. And as the rest time passed the impact strength of microcapsule-contained asphalt was getting higher than that of asphalt without the microcapsule. As the rest time of 15 days passed, the original strength was restored. This tells that microcapsule-contained asphalt had the ability of self-healing. X-ray photos proved that DMP on asphalt fracture surface, which were burst out of the microcapsules when cracks occurred on asphalt, were polymerized to polyphenyleneoxide and this PPO covered the crack and healed the damage.

• Composites Research
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• v.33 no.3
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• pp.91-100
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• 2020

Polyphenylene sulfide (PPS) is a semi-crystalline engineering thermoplastic resin that has outstanding thermal stability, mechanical strength, inherent flame retardancy, chemical resistance, and electrical properties. Due to these outstanding properties, it is preferred as a matrix for composite materials. Many studies have been conducted to produce composites with carbon fibers and glass fibers to improve mechanical properties and provide functionality of PPS. In this review paper, we report a brief introduction to the fabrication and applications of PPS composites with carbon nanotubes, graphene, carbon fibers, and glass fibers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1999-2004
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• 2011

This research aims to develop polymer composites which can be used for PEMFC bipolar plate by injection molding process. Considering the moldability and stiffness, we used LCP(Liquid crystal polymer) as base resin. In order to improve electrical conductivity and mechanical properties, we chose carbon black, and both synthetic graphite and expanded graphite. The composites with different recipe are prepared for injection molding of PEMFC bipolar plate and CAE(Computer Aided Engineering) analysis was performed to predict melt flow and fiber orientation We did successfully fabricate the ASTM specimens by injection molding, and measure the electrical conductivity of the samples by using four point probe device. We measured mechanical properties such as flexural strength, flexural modulus and Izod impact strength. Conclusively, the electrical conductivity increased with increasing additive concentration, but both flexural strength and Izod impact strength decreased due to the brittle nature of carbon-based additives.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1041-1046
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• 2012

In this study, we performed experimental tests on five SP-100 aluminum powder epoxy specimens with several after-curing conditions in order to estimate their hardness with temperature and compressive strength. In the surface hardness test, it was found that the higher the after-curing temperature, the higher was the hardness. In particular, it was found that the hardness of the specimens in cases 3 and 4 was much higher than in the other cases. In addition, in the compression tests carried out to evaluate the compressive strength, it was found that the specimens showed relatively similar stiffness and strength with after-curing, and specimens with no after-curing showed compression stress-strain curves similar to those of thermoplastic resins.

• Composites Research
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• v.36 no.4
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• pp.275-280
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• 2023

Because polymer-based composites are lightweight and have excellent properties, their demand is growing rapidly as a way to fulfill properties that are difficult to achieve with a single material. As a result, there has been a lot of research on polymer nanocomposites, which are made by dispersing particles with a size of 1-100 nm in a polymer matrix. In addition, many nanocomposites using thermoplastic resins as matrix materials are being studied. In this study, poly(ethylene terephthalate) (PET)-based nanocomposites containing organic nanoclays modified with cetyltrimethylammonium bromide (CTAB) as interlayer materials were prepared. Among various nanoclays, vermiculite (VMT) has been studied to increase the mechanical and thermal properties of polymeric materials due to its low cost, abundant reserves and unique properties. However, the strong interlayer bonding of VMT has limited its utilization due to its poor exfoliation and dispersion performance within polymer matrices. In this study, the mechanical properties of the VMT content were confirmed by tensile tests, the dispersion of VMT particles in the PET matrix was evaluated by TEM cross-sectional images, and the nitrogen gas barrier properties were evaluated.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.225-228
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• 2018

Plasticizers added to thermoplastic polymers are known to shorten the life of products due to the elution to outside, and some of them are harmful to our environment and human body. Since the use of phthalate plasticizers suspected of being carcinogens has been gradually prohibited, there is a need for environmentally friendly plasticizers that can replace them. Most of the substances have a low compatibility with resin, high cost and lack of safety verification. Therefore, in this study, four kinds of norbornene dialkyl ester compounds possessing excellent physical properties, which are also reported as safe compounds from the toxicity evaluation, were added to PVC resin to evaluate the possibility of human exposure by leaching, and also the potential usage as plasticizer candidates alternative to commercial ones including DEHP, DINCH and DOTP. The test was carried out according to the American standard test method (ASTM). The results showed that di-2-ethylhexyl-5-norbornene-2,3-dicarboxylate (DEHN) in aqueous solvents and diisopentyl-5-norbornene-2,3-dicarboxylate (DIPN) compounds in oil solvents were superior or equivalent to DEHP. In addition, all four norbornene compounds showed lower values than 100 ppm, which is considered to have an influence on the environment, indicating that the polar norbornene structure affects the elution.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.194-194
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• 2011

현대 사회에서 차량을 비롯한 선박, 항공기와 같은 각종 수송수단들은 그 용도와 형태도 다양하고 널리 보급되어있을 뿐만 아니라 각 분야에서 없어서는 안 될 필수품이 되어 있다. 그러나 수송수단의 수와 활용빈도수가 증가함에 따라 그로 인한 차량화재, 선박화재 그리고 항공기화재 등과 같은 특수화재의 발생에 따른 재산 및 인명피해의 문제점들도 함께 늘어나고 있는 실정이다. 2009년 기준, 1년 동안의 전체 화재발생건수 47,071건 가운데 차량화재의 발생건수가 5,958건으로서 전체의 12.6% 정도를 차지하였다. 그뿐만 아니라 차량 내장재의 주 재질은 가연성을 지닌 열가소성 합성수지들로서 화재가 발생하였을 경우, 다량의 가연성 가스 및 독성가스를 방출하기 때문에 인명 및 재산 피해를 증가시키는 문제점을 갖고 있다. 하지만 아직까지도 이와 같은 수송수단에 대한 화재를 예방하거나 피해를 최소화할 수 있는 화재진압대책 등에 관한 연구는 미흡한 실정이다. 따라서 본 연구에서는 이러한 문제점을 해결하고 과학적이며 체계적인 대응방안을 수립하기 위한 기초 자료를 확보하고 이를 통한 수송수단의 화재안전성을 분석하고자 각종 수송수단에서 사용되는 오일을 대상으로 연소특성 분석 및 화재하중에 관한 연구를 수행하였다. 분석 대상 오일은 연료용과 부속용 오일로 크게 분류되며, 연료용 오일로는 차량용 경유와 휘발유 그리고 군용차량용 경유, 항공기용 백등유와 제트유, 선박용 고유황경유 등을 선정하였다. 부속용 오일로는 브레이크오일, 파워오일, 엔진오일, 자동변속기오일, 수동변속기오일을 대상으로 각각 일반용과 고급형 2가지씩 시료를 선정하여 분석을 수행하였다. 분석방법은 대상오일들의 기초물성을 고찰하기 위해서 비중계를 이용하여 각 시료들의 비중을 측정하였으며, 문헌으로부터 끓는점, 어는점 및 점도 등을 조사하였다. 또한, 대상오일들의 착화특성을 살펴보고자 콘칼로리미터와 인화점 측정기 및 발화점 측정기 등을 이용하여 발열량, 착화시간, 발연량, 발화점, 인화점 등을 측정하였다. 대상오일들의 물성 및 착화특성에 대한 측정결과를 살펴보면, 비중은 $725.8{\sim}1072.0kg/m^3$ 정도의 값을 나타냈고, 인화점은 영하의 인화점을 갖는 휘발유의 경우, 장비의 특성상 분석이 곤란하여 측정하지 못하였으며, 다른 시료들은 $45.3{\sim}266.6^{\circ}C$정도의 값을 나타냈다. 발화점은 $325.7{\sim}600.6^{\circ}C$정도의 값을 갖는 것으로 나타났다. 따라서 이와 같은 결과들을 활용하면 차량, 선박, 항공기 등에 대한 화재발생과 관련된 화재안전성을 분석하고 이를 통한 수송시스템의 화재에 대한 예방 및 대응 방안의 효율성을 높일 수 있을 것으로 생각된다.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.489-501
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• 1997

Electropolymerization of 2-vinylnaphthalene (2-VN) and methylmethacrylate (MMA) with high radiation resistance property was conducted on the surfaces of carbon fibers by using a nonaqueous solution of comonomers dissolved in N,N-dimethylformamide containing sodium nitrate as a supporting electrolyte. The fabrication of carbon fiber/2-VN/MMA prepreg was performed electrochemically in 1:1 comonomer solution. Electropolymerization was conduced by changing the current density, initial comonomer concentration, and reaction time. The weight gain on the surface of the carbon fibers was measured by thermogravimetric analyser (TGA). The highest weight gain of 50 wt% was obtained at 600mA/g~800mA/g current density range, but the weight gain was rapidly decreased above 800mA/g current density. The weight gain was increased with the concentration of comonomer, while the concentration of electrolyte had almost no effect on the weight gain. At 300mA/g current density, weight gain rate was increased abruptly to the initial 30 minutes of reaction time. After that the rate was decreased due to the generation of gas bubbles. In order to check the effect of coated polymers on the radiation resistance, morphology changes before and after $\gamma$-ray irradiation was investigated for the composites.

• Composites Research
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• v.36 no.2
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• pp.126-131
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• 2023

Growing environmental concerns regarding pollution caused by conventional plastics have increased interest in biodegradable polymers as alternative materials. The purpose of this study is to develop a 100% biodegradable nanocomposite material by introducing organic nucleating agents into the biodegradable and thermoplastic resin, poly(lactic acid), to improve its properties. Accordingly, cellulose nanofibers, an eco-friendly material, were adopted as a substitute for inorganic nucleating agents. To achieve a uniform dispersion of cellulose nanofibers (CNFs) within PLA, the aqueous solution of nanofibers was lyophilized to maintain their fibrous shape. Then, they were subjected to primary mixing using a twin-screw extruder. Test specimens with double mixing were then produced by injection molding. Differential scanning calorimetry was employed to confirm the reinforced physical properties, and it was found that the addition of 1 wt% CNFs acted as a reinforcing material and nucleating agent, reducing the cold crystallization temperature by approximately 14℃ and increasing the degree of crystallization. This study provides an environmentally friendly alternative for developing plastic materials with enhanced properties, which can contribute to a sustainable future without consuming inorganic nucleating agents. It serves as a basis for developing 100% biodegradable green nanocomposites.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.505-516
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• 2009

The effects of wood species, particle size of wood flours and coupling treatment on the mechanical properties of wood plastic composites (WPC) are investigated in this study. Chemical components of wood flour from 3 different wood species were analyzed by the chemical analysis. Wood flours of 40~60 mesh and 80~100 mesh were manufactured from Larix (Larix kaempferi Lamb.), Quercus (Quercus accutisima Carr.), and Maackia (Maackia amuresis Rupr. et Maxim). The wood flours were reinforced into polypropylene (PP) by melt compounding and injection molding, then tensile, flexural, and impact strength properties were analyzed. The order of alpha-cellulose content in wood is Quercus (43.6%), Maackia (41.3%) and Larix (36.2%). The order of lignin content in wood is Larix (31.6%), Maackia (24.7%), and Quercus accutisima (24.4%). The content of extractives in wood is in the order of Larix (8.5%), Maackia (4.4%), and Quercus accutisima (3.9%). As the content of alpha-cellulose increases and the lignin and extractives decreases, tensile and flexural strengths of the WPC increase. At the same loading level of wood flours, the smaller particle size (80~100 mesh) of wood flours showed highly improved tensile and flexural strengths, compared to the larger one (40~60 mesh). The impact strength of the WPC was not significantly affected by the wood species, but the wood flours of larger particle size showed better impact strengths. The addition of maleated polypropylene (MAPP) provided the highly improved tensile, flexural and impact strengths. Morphological analysis shows improved interfacial bonding with MAPP treatment for the composites.