• Elastomers and Composites
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• 제33권5호
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• pp.335-344
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• 1998

본 연구에서는 군용 전투차량 궤도 패드용으로 사용되는 고무 배합물의 내크랙성 향상을 위해 기계적 물성이 우수한 천연고무를 이용하여 크랙 개시 저항성 즉, 인열 에너지와 크랙성장 저항성인 크랙 성장 속도를 평가하였다. 내크랙성에 영향을 주는 인자는 여러 가지가 있으나, 본 실험에서는 주로 충전제인 카본블랙과 가교 시스템을 평가하였다. 본 연구결과 촉진제의 함량이 황의 함량과 동일 할 때 내크랙성이 가장 우수하였다. 또한 카본블랙은 보강성이 우수한 hard black의 일종인 ISAF (N220)가 강도 및 가공성에서 가장 우수한 것으로 평가되었으며 적정 함량은 50phr이었다.

• 폴리머
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• 제36권2호
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• pp.235-244
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• 2012

본 연구에서는 thiazole 계 촉진제인 2-mercapto benzothiazole(MBT)의 첨가량을 변화시켜(0, 1, 2, 3, 4 phr) 실란/실리카로 충전된 천연고무 컴파운드에 첨가하여 가황속도, 물성, 고무-충전제간 상호작용계수(${\alpha}_F$), 가교밀도 및 탄젠트 델타($tan{\delta}$)에 미치는 영향을 비교 평가하였다. 촉진제의 첨가량이 증가할수록 $t_{s2}$, $t_{90}$ 가황시간은 빨라졌고 가교 밀도 및 300% 모듈러스는 증가하였다. 인장강도와 신장률 또한 증가하였으나 3 phr에서는 더 이상의 증가가 없었다. 그리고 상온에서의 $tan{\delta}$ 값은 $70^{\circ}C$에서보다 높은 값을 나타내었다. 촉진제의 함량변화는 천연고무-실란/실리카간 상호관계(${\alpha}_F$)에 큰 영향을 미치지 않는 것으로 관찰되었다. 가황속도에 미치는 메카니즘을 고찰하였다.

• 한국농공학회논문집
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• 제58권3호
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• pp.21-27
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• 2016

This study was performed to evaluate engineering properties of carbon and glass fiber reinforced recycled polymer concrete. Fiber reinforced recycled polymer concrete were used recycled aggregate as coarse aggregate, natural aggregate as fine aggregate, $CaCO_3$ as filler, unsaturated polyester resin as binder, and carbon and glass fiber as fibers. The compressive and flexural strength of carbon fiber reinforced recycled polymer concrete were in the range of 68~81.5 MPa and 19.1~21.5 MPa at the curing 7days. Also, the compressive and flexural strength of glass fiber reinforced recycled polymer concrete were in the range of 69.4~85.1 MPa and 19~20.1 MPa at the curing 7days. Abrasion ratio of carbon and glass fiber reinforced recycled polymer concrete were decreased 21.6 % and 11.6 % by fiber content 0.9 %, respectively. After impact resistance test, drop numbers of initial and final fracture were increased with increase of fiber contents. Accordingly, carbon fiber and glass fiber reinforced recycled polymer concrete will greatly improve the hydraulic structures, underground utilities and agricultural structures.

• 멤브레인
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• 제27권3호
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• pp.284-289
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• 2017

본 연구에서는 복합막의 물성향상을 위해 clay를 도입한 polysulfone 나노섬유 복합막을 제조하였다. Polysulfone/clay 복합막은 clay가 들어간 N,N-dimethyl acetamide와 acetone 혼합용매에 polysulfone을 첨가한 후 전기방사법을 이용하여 제조하였으며, 제조된 나노섬유 복합막은 적층수를 변화해 기공크기를 조절한 후 사용하였다. 전반적인 분리막의 특성은 SEM, contact angle, 기공특성, tensile strength, water flux 분석을 사용하여 고찰하였다. 특히 SEM image로 clay의 도입을 확인하였으며 contact angle 측정을 통해 표면이 개질된 결과를 확인할 수 있었다. 그리고 clay의 도입량에 따른 복합막의 기계적 물성을 확인하였다. 따라서 본 연구에서 제조된 분리막은 수처리용 분리막으로 충분히 활용 가능할 것으로 판단된다.

• Macromolecular Research
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• 제14권2호
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• pp.187-193
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• 2006

Organoclay, was applied as a filler, in place of carbon black and silica, to a natural rubber (NR)/butadiene rubber (BR) blend. A compounding method was used to disperse and separate the layered silicates. The effect of a coupling agent on the vulcanizates was evaluated using both the silica and organoclay filled compounds. After the compounding processes were completed, the XRD diffraction peaks disappeared, but then reappeared after vulcanization. The scorch times for the organoclay-filled compounds were very short compared to those for carbon black and silica-filled compounds. The organoclay-filled compounds showed high values of tensile strength, modulus, tear energy, and elongation at the break. When ranked by viscosity, the compounds appeared in the following order: silica > silica (Si-69) > organoclay > organoclay (Si-69) > carbon black. Fractional hysteresis, tensile set, and wear rates were very consistent with the viscosity of the vulcanizates. The Si 69 coupling agent increased reversion resistance, the maximum torque values in the ODR, modulus, and wear resistance, but decreased elongation at the break, fractional hysteresis, and tension set of the vulcanizates.

• Composites Research
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• 제28권3호
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• pp.118-123
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• 2015

In the current study explain about the bio-based composites made by groundnut shell as reinforcement with polyester resin matrix. Groundnut shell is an abundantly available natural waste byproduct and poly ester resin is widely used to fabricate of composites for good balance of mechanical properties because it is relatively low price and ease of handling. Evaluate the mechanical properties of manufactured groundnut shell/polyester composites by varying the amounts (wt %) of groundnut shell. Particulate shell reinforced polyester composites incorporating varying amounts of groundnut shell (5, 10, 15 and 20%) were characterized for their tensile strength, flexural strength, and impact strength. The mechanical properties improved with increasing particle loading up to 15% and decreased thereafter. Increasing in strength with increased particle shell loading was attributed to increase in surface area which enhanced load transfer between the polyester matrix and ground shall particulates. Scanning electron microscopic studies have been carried out to study the morphology of the composite. Thermal studies and water absorption properties of the composites also studied in this paper.

• Restorative Dentistry and Endodontics
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• 제1권1호
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• pp.34-38
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• 1975

Artificial canals were prepared by means of engine reamer on the slab which was made of clear acrylic resin. The shape of this canal is similar to the natural canal, the size is almost same as Kerr File No. 70, and the length is about 20mm. Sealer, Zine oxide eugenol mixture was prepared as matched to spatula test. Lentulo filler was inserted as deep as middle portion and apical one-third portion of the canal and the dental engine was driven in the speed of 1,000 and 3,000 r.p.m. in 30 seconds and 60 seconds with feeding of the sealer. The author measured the excess flow of the canal sealer from Lentulo end. Following are the results obtained from this study. 1. Lentulo insertion at the middle portion 1,000 r.p.m. in 30 seconds case: 0.21mm Same as above in 60 seconds: 0.20mm 2. Lentulo insertion at apical-thirds. 1,000 r.p.m. in 30 seconds: 0.22mm. Same as above in 60 seconds: 0.20mm. 3. Lentulo insertion at middle portion. 3,000 r.p.m. in 30 seconds: 0.14mm Same as above in 60 seconds: 0.25mm. 4. Lentulo insertion at apical-thirds, 3,000 r.p.m. in 30 seconds: 0.11mm Same as above in 60 seconds: 0.27mm.

• 한국공간구조학회논문집
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• 제19권3호
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• pp.41-50
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• 2019

The stone pagoda continued to be damaged by weathering and corrosion over time, and natural disasters such as earthquake are accelerating the destruction of cultural properties. Stone pagoda has discontinuous structure behavior and is very vulnerable to the seismic load acting in lateral direction. It is necessary to analyze various design variables as the contact surface characteristics play an important role in the dynamic behavior of stone pagodas. For this purpose, contact surface characteristics of stone pagoda can be classified according to surface roughness and filler type, and representative model is selected and structural modeling and analysis are performed using the discrete element method. Also, the seismic load according to the repetition period is calculated and the dynamic analysis is performed considering the discontinuous characteristics of the stone pagoda. Finally, the seismic behavior characteristics can be analyzed by the evaluation of stresses, displacements and structural safety.

• Journal of the Korean Wood Science and Technology
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• 제52권4호
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• pp.331-342
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• 2024

Rubberwood (Hevea brasiliensis) has excellent physical and mechanical properties and is one of the most widely used species in Southeast Asia. However, it has poor resistance to subterranean termite attacks due to its high sugar and starch contents. The objective of this study was to evaluate the termite resistance of experimental wood-plastic composite (WPC) panels manufactured from rubberwood flour, polyethylene terephthalate, and silica in three different weight ratios (1/2/7, 1/3/6, and 1/4/5). The panels were exposed to Coptotermes curvignathus subterranean termites in a no-choice test under laboratory conditions based on Indonesian standards. Solid rubberwood used as control samples presented poor resistance, exhibiting 23.1% weight loss due to subterranean termite attack, as indicated by low termite mortality and high wood weight loss. In contrast, the WPC samples demonstrated extreme resistance, with weight loss ranging from 0.19% to 0.23%. Based on the findings of this study, the high termite mortality and overall low mass loss of the samples indicate that such manufactured panels could provide a high level of protection with regard to Indonesian standards.

• 한국수소및신에너지학회논문집
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• 제23권2호
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• pp.134-142
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• 2012

A bipolar plate is a major component of a fuel cell stack, which occupies 50~60% of the total weight and over 50% of the total cost of a typical fuel cell stack. In this study, a composite bipolar plate is designed and fabricated to develop a compact and light-weight direct methanol fuel cell (DMFC) stack for a small-scale Unmanned Aerial Vehicle (UAV) application. The composite bipolar plates for DMFCs are prepared by a compression molding method using resole type phenol resin as a binder and natural graphite and carbon black as a conductor filler and tested in terms of electrical conductivity, mechanical strength and hydrogen permeability. The flexural strength of 63 MPa and the in-plane electrical conductivities of 191 S $cm^{-1}$ are achieved under the optimum bipolar plate composition of phenol : 18%; natural graphite : 82%; carbon black : 3%, indicating that the composite bipolar plates exhibit sufficient mechanical strength, electrical conductivity and hydrogen permeability to be applied in a DMFC stack. A DMFC with the composite bipolar plate is tested and shows a similar cell performance with a conventional DMFC with graphite-based bipolar plate.