• Applied Biological Chemistry
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• v.46 no.2
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• pp.113-116
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• 2003

Color value, total color difference $({\triangle}E)$, puncture strength (PS), tensile strength (TS), percent elongation(%E) at break values, and water vapor permeability (WVP) were determined for water-soluble chitosan films added with soy protein isolate (SPI) and $CaCl_2$. Mechanical and water vapor barrier properties of the chitosan films were affected by SPI and $CaCl_2$ concentrations. PS value $(174.5-448.8\;g_f)$ of the chitosan films increased with increasing concentration of $CaCl_2$ TS value of 0.05% $CaCl_2$-added chitosan films significantly increased to 1.58 MPa compared to 0.06 MPa of the control. %E values ranged from 12.25 to 44.80% and increased with increasing concentration of $CaCl_2$. WVP of $CaCl_2$-added films was lower than that of SPI-added films.

• Journal of Conservation Science
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• v.28 no.3
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• pp.235-245
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• 2012

Nondestructive deterioration diagnosis has been carried out for the former ore dressing plant of the Yongwha mine in Yeongyang (Registered Cultural Property No. 255). Deterioration rates about organic contaminant and soil of the upper part (7 to 13 layer) indicate higher than the lower part (1 to 6 layer) of the ore dressing plants. By contrast, deterioration rates such as crack, break out and discoloration of the lower part indicate very higher than the upper part. It is estimated that the plants of the lower part that mechanical and chemical process had been done for flotation were damaged severely by physicochemical weathering with reaction of concrete and chemical solution. As results of ultrasonic velocity measurement, average p-wave velocity of plants were measured 2,462m/s (compressive strength $529kgf/cm^2$). As for the analytical results of surface contaminants and soil compositions using P-XRF, they were identical with major elements (Cu, Zn, Pb, Fe and As) of ore minerals from the Yongwha mine. Therefore, the ore dressing plant should be treated by phytoremediation with conservation because heavy metals could impinged upon plants and natural environment.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.530-537
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• 2014

Moisture is a major factor causing the deteriorative physical change, microbial growth, and chemical reaction of the products. In this study, the moisture absorbing composite films have been prepared with moisture absorbing material of polyacrylic acid partial sodium salt (PAPSS) impregnated on LLDPE polymer for the functional packaging applications. The results showed that PAPSS impregnated film illustrated uniformly dispersed PAPSS particles in the LLDPE polymer matrix. The transparency of the PAPSS impregnated film decreased slightly at higher PAPSS concentrations. An increase in the PAPSS content for moisture-absorbing films showed a similar decrease in tensile strength, percent elongation at break, and tear strength. Their values of films impregnated with PAPSS of 0.5, 1, and 2% showed no significant difference. Meanwhile, 4% PAPSS films significantly decreased the values of mechanical properties compared to the films impregnated with different PAPSS levels. Values of the oxygen permeability and water vapor permeability for PAPSS impregnated films decreased significantly with greater PAPSS. The results indicate that 4% PAPSS impregnated in LLDPE films had high affinity of moisture absorbencies compared to the other films. The mathematical equation that best described the moisture sorption isotherm of each film sample was the GAB equation at $25^{\circ}C$. The crystallization and melting temperatures of PAPSS films were influenced by the addition of PAPSS material, but showed good thermal stability.

• Elastomers and Composites
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• v.49 no.1
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• pp.24-30
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• 2014

3-Amino-1,2,4-triazole (ATA) (2.5 and 5.0 phr) was incorporated into a immiscible maleated ethylene propylene diene rubber(mEPDM)/maleated high density polyethylene(mHDPE) (50 wt%/50 wt%) blend by melt mixing. Effects of the ATA on structure, mechanical and rheological properties of the blend was investigated. FT-IR and DMA results revealed that supramolecular hydrogen bonding interactions between the polymer chains occur by reaction of ATA with maleic anhydride grafted onto the component polymers in the blend, which induces the physical crosslinks in the blend. FE-SEM analysis showed that mEPDM forms a dispersed phase in continuous mHDPE matrix, and the blend with the ATA has finer phase morphology as compared to the blend without the ATA. By the addition of ATA in the blend, there were significant increases in tensile strength, modulus and elongation-at-break as well as elastic recoverability. Melt rheology studies revealed that ATA induced substantial increase in storage modulus and complex viscosity of the blend at the melt state.

• Polymer(Korea)
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• v.33 no.5
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• pp.446-451
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• 2009

Reliability evaluations of linear low density polyethylene (LLDPE) pipe with respect of thermal exposure time have been investigated in accordance with RS M 0042, which is a reliability standard for polymer pipe. As the thermal exposure time is prolonged, a progressive increase, until 250 days, in tensile strength and a slight increase in hardness are observed, while a proportional decrease in elongation at break is showed. These results can be explained by the increase of crystallinity, followed by the increase of crosslinking density, chain scission and the decrease in chain mobility, due to thermal oxidation as the exposure time increases. Long term hydrostatic pressure test result implies the existence of transition point from ductile to brittle fracture. Oxidation induction time (OIT) test is employed to monitor the thermo-oxidative degradation of LLDPE pipe. This result shows that after the exposure time is 250 days, the depletion of antioxidants added in LLDPE pipe occurs. An empirical equation as function of exposure time, under $100^{\circ}C$ thermal-degradation condition, is proposed to assess the remaining amount of antioxidants owing to thermo-oxidative degradation. Fourier transform infrared spectroscopy results show the increase of carbonyl (-C=O) and hydroxyl (O-H) function groups on the surface of thermally exposed LLDPE pipe. This result suggests that the hydrocarbon groups locally undergo the oxidation on the LLDPE surface due to thermal-degradation.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.2
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• pp.61-66
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• 2017

Poly lactic acid(PLA) and poly butylene adipate-co-terephthalate(PBAT) film was prepared using a twin extruder. PLA (25%) and PBAT (75%) were mixed with various ratio of chain extenders, such as $Joncryl^{(R)}$ and hexamethylene diisocyanate(HDI) to improve the mechanical and thermal properties of produced bio composite films. Tensile strengths of films were steadily increased with increasing ratio of chain extender. The tensile strength of control films was about 25 MPa, and the tensile strength of films with combined chain extenders was above 40 MPa. The films with $Joncryl^{(R)}$ resulted in improved tensile strength, while the film with HDI alone showed improved percent elongation at break. By adding chain extenders into PLA/PBAT resin, the cold crystallization temperature (Tcc) and decomposition temperature (Td) of the produced bio composite films increased. It revealed that the addition of two types of chain extenders was efficient way to get PLA/PBAT film with improved strength and elongation.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.673-680
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• 2019

GAP or GAP-co-BO based energetic thermoplastic elastomers (ETPEs) were synthesized by changing the hard segment content percent in the range of 30~45% by 5% difference. Thermal and mechanical properties of GAP-co-BO based ETPEs were compared to those of GAP based ETPEs. FT-IR results showed that the capability of forming hydrogen bond increases with increasing the hard segment content in GAP/GAP-co-BO based ETPE, and also the GAP-co-BO based ETPEs are stronger than GAP based ETPEs in the hydrogen bond formation. DSC and DMA results showed that the glass transition temperature (T_g) of GAP based ETPEs increased with the increment of the hard segment content, while the T_g of GAP-co-BO based ETPEs was maintained even the hard segment content increased. The storage modulus at room temperature of the GAP-co-BO based ETPEs was higher than that of the GAP based ETPEs. This was due to the strong phase separation behavior of the hard and soft segment of GAP-co-BO based ETPEs, which further resulted in the stronger breaking strength and lower tensile elongation at break point for GAP-co-BO based ETPE than the GAP based one.

• Korean Journal of Environmental Agriculture
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• v.18 no.3
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• pp.265-271
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• 1999

The direct seeding of seeds or the pellets of three native tree species (Pinus densiflora, Parthenocissus tricuspidata and Rhus chinensis) was tried on the rock cut-slope revegetation bed established by construction of mechanical excavation or erosion break with artificially enriched soil medium. The seed $pellet(1{\sim}2\;cubic\;cm)$ made by coating seeds(treated with proper previous pregermination treatments) with the mixture of peatmoss, clay, chemical absorbant(3.5:1.0:0.2, v/v) showed about twice better percent germination than the control seeds. The percent germination and the survival rate of the germinated seedlings were higher in the spring direct seeding than the summer or the fall. The soil medium containing the compost showed extremely low percent $germination(0{\sim}3%)$ which presumably attributed to the compost inducing damping-off disease. The survival rates were affected mainly by shading of natural herbaceous vegetation invading from outside to the revegetation bed. The planting of two year old container seedlings of P. densiflora and P. tricuspidata on August 2, 1998 was successful indicating that it could be an alternative revegetation method in case the summer direct seeding is unfavorable.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.63-70
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• 2015

This paper proposes a novel airfoil named "KA2" for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

• Elastomers and Composites
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• v.48 no.1
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• pp.39-45
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• 2013

Melt grafting of citraconic acid (CCA) onto an ethylene-propylene-diene terpolymer (EPDM) with various peroxide initiators was performed using a Haake Rheocorder. Finding the optimum running condition and concentration is critical for effective grafting and performance of grafted material. Therefore, this study focused on the effects of mixing (reaction) condition and monomer/initiator dosages on the grafting degree, grafting efficiency and crosslinking degree (gel content), melt flow index and mechanical properties of CCA-g-EPDM. As the grafting degree/crosslinking degrees increased, the tensile strength increased significantly, but elongation at break and melt flow index decreased. The initiator 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane (T-101) appeared to meet for the best grafting(2.31%). The grafting degree increased markedly with increasing monomer CCA/initiator T-101 contents. The grafting degree also increased with increasing mixing temperature/time, and then leveled off or decreased/increased a little. The optimum monomer/initiator dosages and reaction temperature/time were found to be about 5/0.05 wt% and $180^{\circ}C$/15min, respectively.