• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.146-149
• /
• 2007

The 2-step manufacturing method consisting of preforming and stamping processes was developed to manufacture composite bipolar plates for PEMFCs. The preform was composed of expanded graphite, graphite flake and phenol resin. Precuring conditions were optimized by checking the electrical conductivity, flexural strength and microstructure. Precuring temperature ($100^{\circ}C$) slightly above the melting point of phenol powders ($90^{\circ}C$) induced moderate curing, but also prevented excessive curing. Preforms utilizing the tangled structure of expanded graphite were easily fabricated at low pressure of 0.07-0.28MPa. The proper precuring time, 5min, was determined to fabricate the preform stably because insufficient and excessive precuring deteriorated the flexural strength of composite bipolar plates.

• Elastomers and Composites
• /
• v.50 no.4
• /
• pp.258-264
• /
• 2015

Rubber composites were prepared by precured CIIR pulverized at knead shear force in order to research the effects of the BR/PCP composites. The particle size of domain in BR/CIIR composites was decreased and homogeneously dispersed by the precured CIIR pulverized. However, it was difficult to use the product when the content is 40 phr and precured of 40%. BR/PCP composites have improved mechanical properies as compared that of the addition of simply cut chip composite.

• Elastomers and Composites
• /
• v.53 no.2
• /
• pp.67-74
• /
• 2018

Magneto-rheological elastomers (MREs) are smart materials in which the inherent stiffness and damping properties can be changed by the influence of an external magnetic field. The magneto-rheological (MR) effect depends on the orientation characteristics of the dispersed magneto-responsible particles (MRPs) in the matrix. In this study, natural rubber (NR) and ethylene propylene diene rubber (EPDM) were blended and used as a matrix of an MRE. EPDM was pre-cured before blending with NR. The Mooney viscosity, curing characteristics, and mechanical properties were analyzed with various pre-curing conditions of EPDM and the NR/EPDM blend. The results show that excellent mechanical properties of the NR/EPDM blend-based MRE were obtained when the pre-curing time of EPDM was 60 min. The aging property of the NR-based MRE was improved by the introduction of pre-cured EPDM. Also, the anisotropic MRE showed a higher MR effect than that of the isotropic MRE.

• Fibers and Polymers
• /
• v.7 no.4
• /
• pp.380-388
• /
• 2006

Fully biodegradable and environment-friendly green composite specimens were made using ramie fibers and soy protein concentrate (SPC) resin. SPC was used as continuous phase resin in green composites. The SPC resin was plasticized with glycerin. Precuring and curing processes for the resin were optimized to obtain required mechanical properties. Unidirectional green composites were prepared by combining 65% (on weight basis) ramie fibers and SPC resin. The tensile strength and Young's modulus of these composites were significantly higher compared to those of pure SPC resin. Tensile and flexural properties of the composite in the longitudinal direction were moderate and found to be significantly higher than those of three common wood varieties. In the transverse direction, however, their properties were comparable with those of wood specimens. Scanning electron microscope (SEM) micrographs of the tensile fracture surfaces of the green composite indicated good interfacial bonding between ramie fibers and SPC resin. Theoretical values for tensile strength and Young's modulus, calculated using simple rule of mixture were higher than the experimentally obtained values. The main reasons for this discrepancy are loss of fiber alignment, voids and fiber compression due to resin shrinking during curing.

• Journal of Korean Society on Water Environment
• /
• v.25 no.6
• /
• pp.886-895
• /
• 2009

The guideline of selection of Integrated Management Practices (IMPs), such as wood, green roof, lawn, and porous pavement, for Low Impact Development (LID) design was proposed by ranking the reduction rate of surface runoff using LIDMOD1.0. Based on the guideline, LID was designed with several scenarios at two apartment complexes located at Songpa-gu, Seoul, Korea, and the effect of LID on surface runoff was evaluated during last 10 years. The effect of runoff reduction of IMP by land use change was highly dependent on the kind of hydrologic soil group. The wood planting is the best IMPs for reduction of surfac runoff for all hydrologic soil groups. Lawn planting is an excellent IMP for hydrologic soil group A, but reduction rate is low where soil doesn't effectively drains precipitation. The green roof shows constant reduction rate of surface runoff because it is not influenced by hydrologic soil group. Compared to the rate of other IMPs, the green roof is less effect the surface runoff reduction for hydrologic soil group A and is more effect for hydrologic soil group C and D followed to planing wood. The porous pavement for the impervious area is IMPs which is last selected for LID design because of the lowest reduction rate for all hydrologic soil group. As a result of LID application at study areas, we could conclude that the first step of the strategy of LID design at apartment complex is precuring pervious land as many area as possible, second step is selecting the kind of plant as more interception and evapotranspiration as possible, last step is replacing impervious land with porous pavement.

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

• Composites Research
• /
• v.20 no.2
• /
• pp.10-16
• /
• 2007

The 2-step manufacturing method consisting of preforming and stamping processes was developed to manufacture composite bipolar plates for PEMFCS. The preform was composed of expanded graphite, graphite flake and phenol resin. Procuring conditions were optimized by checking the electrical conductivity, flexural strength and microstructure. Procuring temperature $(100^{\circ}C)$ slightly above the melting point of phenol powders $(90^{\circ}C)$ induced moderate curing, but also prevented excessive curing. Preforms utilizing the tangled structure of expanded graphite were easily fabricated at low pressure of 0.07-0.28MPa. The proper procuring time, 5min, was determined to fabricate the preform stably because insufficient and excessive procuring deteriorated the flexural strength of composite bipolar plates.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.6
• /
• pp.319-326
• /
• 2017

In this study, a lightweight geopolymer was prepared using by slag discharged from IGCC (Integrated Gasification Combined Cycle) power plant and its physical properties, the density and compressive strength, were analyzed as a function of the concentration of alkali activators, W/S ratio and aging times. Also the possibility of applying it to lightweight materials by adding Si sludge as a foaming agent to the geopolymerg was investigated. In particular, a complex composition of alkali activator and a pre-curing process were applied to improve the strength properties of lightweight geopolymers. While the compressive strength of the lightweight geopolymer using a single activator was 9.5 MPa, the specimen made with a complex composition of alkali activator had compressive strength of 2~5 times higher. In addition, the lightweight geopolymer with pre-curing process showed a compressive strength value of 18~48 % higher than that of specimen made with no precuring process. In this study, by using a complex activator and a pre-curing process. the maximum compressive strength of lightweight geopolymer was obtained as 40 MPa (The specimen was aged for 3 days and had density of $1.83g/cm^3$), which is comparable to cement concrete. By analyzing the crystal phase and microstructure of geopolymers obtained in this study using by XRD and SEM, respectively, it was confirmed that the flower-bud-like zeolite crystal was homogeneously distributed on the surface of the C-S-H gel (sodium silicate hydrate gel) in the geopolymer.