• 대한화학회지
• /
• 제16권3호
• /
• pp.166-177
• /
• 1972

This paper reports the reaction of monoiodoperfluorocycloakense with alkyl lithium and activated copper repectively resulting in various coupling products. Of particular interests are compounds of the following composition. The physical properties of the various compounds are given along with a discussion relating to the mechanistic pathways involved in the coupling reactions.

• Applied Biological Chemistry
• /
• 제33권2호
• /
• pp.174-176
• /
• 1990

Oxidation of artemisinic acid was attempted with chromium trioxide-pyridine complex. Epi-Deoxyarteannuin B was formed almost quantitatively, while expected keto artemisinic acid was not the major product. The physical and spectral data of the product are presented(Received March 9, 1990, Accepted May 25, 1990)

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
• /
• pp.61.1-61
• /
• 1998

• 대한화학회지
• /
• 제63권3호
• /
• pp.220-225
• /
• 2019

• Carbon letters
• /
• 제13권4호
• /
• pp.212-220
• /
• 2012

Orange peel (OP) exhibits a sorption capacity towards anionic dyes such as reactive blue 19 (RB19). Cetyltrimethylammonium bromide (CTAB) as a cationic surfactant was used to modify the surface nature of OP to enhance its adsorption capacity for anionic dyes from an aqueous solution. Four adsorbents were investigated: the OP, sodium hydroxide-treated OP (SOP), CTAB-modified OP and CTAB-modified SOP. The physical and chemical properties of these sorbents were determined using nitrogen adsorption at 77 K and by scanning electron microscope and Fourier transform infrared spectroscopy techniques. The adsorption of the RB19 dye was assessed with these sorbents at different solution pH levels and temperatures. The effect of the contact time was considered to determine the order and rate constants of the adsorption process. The adsorption data were analyzed considering the Freundlich, Langmuir, Elovich and Tempkin models. The adsorption of RB19 by the assessed sorbents is of the chemisorption type following pseudo-first-order kinetics. CTAB modification brought about a significant increase in RB19 adsorption, which was ascribed to the grafting of the sorbent with a cationic surfactant.

• Elastomers and Composites
• /
• 제58권4호
• /
• pp.208-215
• /
• 2023

In this study, the properties of polyurethane-polydimethylsiloxane (PU-PDMS) hybrid foams containing different types and contents of physical blowing agents (PBAs) were investigated. Two types of blowing agents, namely physical blowing agents and thermally expandable microspheres (TEM), were applied. The apparent density was measured using precisely cut foam samples, and the pore size was measured using image software. In addition, the microstructure of the foam was confirmed via scanning electron microscopy and transmission electron microscopy. The thermal conductivities related to the microstructures of the different foams were compared. When 0.5 phr of the hydrocarbon-based PBA was added, the apparent density and pore size of the foam were minimal; however, the pore size was larger than that of neat foam. In contrast, the addition of 3 phr of TEM effectively reduced both the apparent density and pore size of the PBAs. The increase in resin viscosity owing to TEM could enhance bubble production stability, leading to the formation of more uniform and smaller pores. These results indicate that TEM is a highly efficient PBA that can be employed to decrease the weight and pore size of PU-PDMS hybrid foams.

• 농업과학연구
• /
• 제49권4호
• /
• pp.667-676
• /
• 2022

The soil physical and chemical properties are the main factors that influence plant productivity and soil fertility. Since 1999, South Korea has been conducting a survey on changes in the agricultural environment survey every four years. The purpose of the present study is to monitor the physical and chemical properties of soil in Chungcheongbuk-do. Soil samples were collected from the exact sites of the aforementioned environment survey, and land use and cultivated crops were also investigated. From a Pearson correlation analysis, it was found that the total carbon contents were most negatively affected by the soil depth. The bulk density of soil increased up to a depth of 40 cm but decreased to a depth of 60 cm. The porosity and moisture of soil generally decreased, but the porosity increased at a depth of 50 - 60 cm. Chemical properties of soil gradually decreased with an increase of the soil depth from 0 to 70 cm, but little change was observed in soil pH with soil depth. In addition, the organic matter contents of the soil at a depth of 30 cm or more were below the optimal range. The soil of Chungcheongbuk-do thus requires organic matter application as a whole, and correction of items that are partially out of the optimal range is necessary.

• Bulletin of the Korean Chemical Society
• /
• 제35권11호
• /
• pp.3349-3352
• /
• 2014

• Elastomers and Composites
• /
• 제29권3호
• /
• pp.213-225
• /
• 1994

The Purpose of this dissertation is to study the preparation technique and physical properties of expanded rubber. The respective samples of NR, NBR and the standard compounds of EPDM rubber were prepared by mixing plasticizer DOP and LCR in various ratio. And their vulcanization characteristics, physical properties and foaming states were studied. Vulcanization characteristics were investigated using cure curve that had been obtained from Oscillating Disk Rheometer study, and the microscopic photographs of foaming states were obtained using electron microscope. The vulcanization characteristics of the samples, DOP 30phr and LCR 30phr, were found to be suitable. The tests, like hardness test and resilience, tensile test on the physical properties of each sample showed that plasticizing efficiencies of DOP and LCR were almost the same. Oil resistance test exhibited DOP was better than LCR and compression set test showed LCR was excellent plasticizer. The foaming states of NR, EPDM compounds were uniform, but those of NBR compounds were not uniform. Consequently vulcanization characteristics, physical properties and foaming states of all the samples satisfied the SAE requirements.

• Bulletin of the Korean Chemical Society
• /
• 제25권7호
• /
• pp.1046-1050
• /
• 2004

Six physical properties (enthalpy, density, decomposition temperature, solubility in water, pKa values, and hydronium potential) were examined by molecular modeling techniques. The molecular connectivity index, Wiener distance index, and Ad hoc descriptor are employed as structural parameters to encode information about branching, size, cyclization, unsaturation, heteroatom content, and polarizability. This paper examines the correlation of the molecular modeling techniques parameters and the physicochemical properties of amino acids. As a results, calculated values were in agreement with experimental data in the above six physical properties of amino acids and the molecular connectivity index was superior to the other indices in fitting the calculated data.