• Polymer(Korea)
• /
• v.29 no.3
• /
• pp.271-276
• /
• 2005

Polypropylene (PP)/montmorillonite (MMT) nanocomposites were prepared by melt mixing methods. MMT modified by dimethyl hydrogenated tallow 2-ethylhexyl ammonium (Cloisite 15A) was used. Polyolefine oligomer with telechelic OH groups was used as a compatibilizer. The degree of dispersion of MMT in the nanocomposites was measured by X-ray diffractometer and transmission electron microscope (TEM) images. MMT was well exfoliated when the contents of compatibilizer was 25 phr. The thermal stability that observed by thermogravimetric analysis (TGA) increased with the contents of MMT increased up to 5 phr. The complex viscosities and storage moduli of PP nanocomposites enhanced as the contents of compatibilizer decreased and those of MMT increased.

• Korean Chemical Engineering Research
• /
• v.47 no.2
• /
• pp.203-207
• /
• 2009

In the NCAs(non-conductive adhesive) for adhesion of Micro Electro Mechanical System(MEMS), there are some problems such as delamination and cracking, because of the differences of CTE(coefficients of thermal expansion) between NCAs and substrates. Addition of inorganic particle or flexibilizer have been performed to solve those problems. In this study, to improve the flexibility of epoxy adhesive, epoxy/siloxane composites were prepared by adding 1, 3, or 5 phr of amino modified siloxane(AMS). Glass transition temperatures(Tg), moduli and CTE of those composites were measured to confirm effects of siloxane on thermal/mechanical properties of siloxane/epoxy-composites. Tg of AMS/epoxy-composites decreased from $134^{\circ}C$ to $122^{\circ}C$ with increasing AMS contents and moduli decreased from 2,425 MPa to 2,143 MPa with increasing AMS contents. But CTE of AMS/epoxy-composites increased from $67ppm/^{\circ}C$ to $71ppm/^{\circ}C$ with increasing AMS contents. In short, the addition of siloxane is effective for enhancing the flexibility of epoxy but leads to the decrease of Tg.

• Resources Recycling
• /
• v.17 no.5
• /
• pp.11-18
• /
• 2008

The purpose of this study was to evaluate the effects of blast-furnace slag on chemical attack and carbonation of latex-modified concrete (LMC) and ordinary portland cement concrete as slag contents. Main experimental variables were performed latex contents (0%, 15%) and slag contents (0%, 30%, 50%). The compressive strengths, chemical attacks resistance and carbonation depth were measured to analyze the characteristic of the developed LMC and BS-LMC(latex-modified concrete added blast-furnace slag) on hardened concrete. The test results showed that compressive strength of BS-LMC with blast-furnace slag content 30% was quite similar to it of OPC without slag content. The structural quality deterioration was concerned when blast slag content was up to 50%. However, carbonation restraint of BS-LMC with blast-furnace slag 30% was bigger then that of opc. Also, the effects of added latex on OPC and BS-LMC were increased on the carbonation restraint and chemical attacks resistance.

• Korean Journal of Soil Science and Fertilizer
• /
• v.44 no.5
• /
• pp.773-778
• /
• 2011

Long-term continuous application of livestock by-products to agricultural land may adversely affect the soil characteristics and the crop yield. Five year term study from 2007 was carried out to assess the effects of repeated application of low-concentration swine slurry on soil chemical properties including phosphate and heavy metal contents and yield of tomato (Lycopersicon esculentum) and cucumber (Cucumis sativus L.) in a greenhouse. Treatments were conventional chemical fertilizers and three application rates of low-concentration swine slurry (Slurry composting and biofiltration, SCB): 50%, 100%, and 200% of recommended nitrogen fertilization. For swine slurry treatment of 50% nitrogen, deficient nitrogen was supplemented with urea fertilizer. The soil phosphorus and heavy metal contents after five year continuous application of swine slurry were not significantly higher than those of chemical fertilizer use. Repeated application of the swine slurry alone for five years resulted in relatively high soil exchangeable potassium and sodium compared with chemical fertilizer treatment. Contents of heavy metals in leaves of tomato and cucumber did not show significant difference among treatments. Yields of the crops for the swine slurry were not significantly different from that of chemical fertilizer. The results imply that continuous application of the swine slurry may not influence levels of soil phosphate and trace elements in greenhouse soils but could accumulate potassium and sodium in the soil.

• Journal of the Korean Chemical Society
• /
• v.43 no.3
• /
• pp.340-350
• /
• 1999

This study was to analyze the articulation between chemistry contents of science textbooks at elementary and middle school level, to survey students ? perceptions on chemistry concepts, to establish guidelines for science textbooks that not only meet the needs of learners but also fit in a coherent way. In order to do this, we analyzed links of the aims and the organization of chemistry contents of elementary and middle school science textbooks, we also surveyed students' perceptions on chemistry concepts students had retained. The study revealed that the 6th middle school curriculum was almost a duplicate of the elementary school syllabus. And there was no interrelation between the organization of chemistry contents and the aim of the chapter which built up a logical picture of the world at a molecular level. It was also found that the lack of coherence between science textbooks in elementary and middle school was a major cause of student difficulty.

• Journal of Life Science
• /
• v.10 no.5
• /
• pp.447-455
• /
• 2000

A eight weeks feeding experiment was conducted to investigate the effects of different dietary dimethyl-$\beta$-propiothetin (DMPT) levels on growth and chemical components in red sea bream (Pagrus major). The content of DMPT extracted from Ulva pertusa by auroclaving was 32.5mg%. Body weight gain, feed efficiency and feed intake were significantly increased with dietary DMPT level. After eight weeks of feeding trial, moisture content decreased with supplemented DMPT level, while crude protein and lipid contents increased with dietary DMPT level. Amino acid contents of muscle was elevated in the DMPT added groups compared to control group. Amino acid composition of muscle in fish fed the diets supplemented DMPT was not different to that of control group. Fatty acid contents of muscle in fish increased with dietary DMPT level.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.4
• /
• pp.110-120
• /
• 1997

One of the most important factor for the comfort of the passenger vehicles is the minimization of the compressible transmissibility during the running vehicles. Seat foam materials of I2 series(index 95 and the contents of isocyanate TDI was changed in percentages 75, 70, 65, 60, 50, 40) and DI series(density 50kg/$\textrm{m}^3$, index was changed 100, 95, 90) showed the significant differences in their transmissibility depended upon their chemical constitution such as index and contents of isocyanate TDI. The minimum trasmissibility of seat foam materials of I2 series was found from the materials with the contents of 65% isocyanate TDI and the index 95 at the frequency 4.79~5.31Hz. Also the minimum transmissibility of seat foam materials of DI series was found from the materials with the index 90 and the density of 50kg/$\textrm{m}^3$ at the frequency of 4.79~5.31Hz.

• Economic and Environmental Geology
• /
• v.27 no.5
• /
• pp.441-449
• /
• 1994

The tourmalines distributed in the Sangdong area belong to the dravite-schorl series in terms of the cell dimensions and the chemical compositions. Geochemical characteristics of tourmalines indicate that Naedeogni granite and pegmatite appear to be derived from Li-poor and Fe-riched aplite rocks, but Nonggeori granite is derived from Ca-poor or Si-riched pelitic rocks. The Mg+Fe contents of tourmaline in Naedeogni granitoids are decreased from the granites to the pegmatites with the Fe contents increased while Mg contents decreased. It indicates the differentiation during the crystallization of tourmalines. These phenomena are coincided with the chemical variations from cores toward rims of the zonal tourmalines. Such a compositional variations in Nonggeori granite can not be observed.

• Journal of Life Science
• /
• v.10 no.6
• /
• pp.548-557
• /
• 2000

A eight weeks feeding experiment was conducted to investigate the effects of different dietary dimethyl-$\beta$-propiothetin (DMPT) levels on growth and chemical components in Korean rockfish (Sebastes schlegeli). The content of DMPT extracted from Enteromorpha intestinalis by autoclaving was 31.1 mg%. Body weight gain and feed efficiency were significantly increased with dietary DMPT level. After eight weeks of feeding trial, moisture content decreased with supplemented DMPT level, while crude protein and lipid contents increased with dietary DMPT level. Amino acid contents of muscle was elevated in the DMPT added groups compared to control group. Amino acid composition of muscle in fish fed the diets supplemented DMPT was not different to that of control group. Fatty acid contents of muscle in fish increased with dietary DMPT level.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.1
• /
• pp.107-111
• /
• 2011

Polypropylene(PP)/carbon fiber(CF)/multi-walled carbon nanotube(MWCNT) nanocomposites along with various CF and MWCNT contents were prepared in a Twin screw extruder. Electrical, mechanical property and morphology were investigated with a variation of CF and MWCNT contents. From the surface resistance of PP/CF/MWCNT composites, MWCNT can increase the conductivity of composites compared with PP/CF composites without MWCNT. It is suggested that MWCNT and CF can make the conductive network in the polymer matrix. Flexural modulus and Izod impact strength of the PP/CF/MWCNT composites were improved with the increase of CF contents. Morphology showed that length of CF in polymer matrix was shortened by torque during melt mixing with MWCNT. As a result of this phenomenon, the impact strength of composites was somewhat decreased.