• Title/Summary/Keyword: Siloxanes

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Solvent Selection for the Detection of Siloxanes in Landfill gas (매립가스내 규소화합물류 검출을 위한 용매선택에 관한 연구)

  • Kim, Nack-Joo;Choi, Ju-Mi;Ji, Eun-Jung
    • Journal of Korean Society of Environmental Engineers
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    • v.29 no.8
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    • pp.915-921
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    • 2007
  • As a preliminary measurement of siloxanes in landfill gas(LFG), this study was conducted to determine the best suitable solvent applicable to the extraction of siloxanes in the domestic landfill using liquid-absorption method. Three solvents of n-hexane, acetone, and methanol were tested and the results obtained from GC analysis for each solvent were compared to their properties. Results showed that the resolution in the GC spectrum was the best from methanol due to the lack of overlapping of the peaks between silane and solvent. The detected siloxanes concentration were varied at maximum 2.6 times depending on the types of solvent as well as extraction velocity and impinger steps. In total, the highest concentration of siloxanes was obtained from methanol, which showed ideal pattern in the absorption of each impinger step and the least relative standard deviation. Accordingly, it is concluded that methanol is the most suitable solvent for the extraction of siloxanes in the domestic landfill. However, it is considered that solvent suitability can vary depending on the waste components and landfill record in landfills.

Determination of Siloxanes in Biogas by Solid-phase Adsorption on Activated Carbon

  • Kim, Nack-Joo;Chun, Seung-Kyu;Cha, Daniel K.;Kim, Cheal
    • Bulletin of the Korean Chemical Society
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    • v.34 no.8
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    • pp.2353-2357
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    • 2013
  • The objective of this study was to develop a simple, less time-consuming and accurate sampling technique based on solid-phase sorption with activated carbon as the sorbents. The results from solid-phase sorption techniques were compared to that from a conventional solvent impinger-based technique to confirm the efficacy of the proposed method. The laboratory results indicated that the solid-phase sorption method was suitable for the determination of siloxanes as the measured concentrations were similar to that from a solvent impinge method. The data from solid-phase sorption method showed excellent recovery and reproducibility while the sampling was less labor intensive and less time consuming than the solvent impinge method. Following the laboratory tests, the solid-phase sorption technique was successfully applied to sampling biogas from a field site. This study shows that the activated carbon-based solid-phase sorption can be a reliable and less time-consuming option for the sampling and collection of siloxanes under various different landfill conditions.

Synthesis of Epoxy Functional Siloxane and its Effect on Thermal Stress

  • Hyun, Dae-Sup;Jeong, Noh-Hee
    • Journal of the Korean Applied Science and Technology
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    • v.26 no.4
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    • pp.379-384
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    • 2009
  • Epoxy resin based encapsulants are widely used in semiconductor packaging applications. Epoxy resin based encapsulants are often subject to crack or delamination during the reliability test due to the thermal stress caused by high modulus nature of epoxy resins. Epoxy functional siloxanes are often added into epoxy resin to reduce the modulus so that the thermal stress can be reduced. Epoxy functional siloxanes, additives for reduced modulus, were synthesized and added into the curable epoxy resins. The modulus and the coefficient of thermal expansion (CTE) were also measured to investigate the thermal stress and to see whether the epoxy functional siloxane adversely affects the CTE or not. As a result, around 26% to 72% of thermal stress reduction was observed with no adverse effect on CTE.

Removal of Volatile Organic Silicon Compounds (Siloxanes) from Landfill Gas by Adsorbents (흡착제에 의한 매립가스 중 휘발성 유기규소화합물(실록산) 제거특성)

  • Seo, Dong-Cheon;Song, Soo-Sung;Won, Jong-Choul
    • Journal of Korean Society of Environmental Engineers
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    • v.31 no.9
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    • pp.793-802
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    • 2009
  • Adsorption properties were estimated for the organic silicon compounds (siloxanes) in an actual landfill gas (LFG) using adsorbents such as coconut activated carbon, coal activated carbon, silica gel, sulfur adsorbent, carbonized sludge, and molecular sieve 13X. Coconut activated carbon showed the highest removal efficiency of more than 95%. The desorption of hexamethyldisiloxane (L2) from the adsorbent, however, resulted in the remarkable concentration variation of the compound in the treated gas. Silica gel, which had high adsorption capacity for L2 in single substance adsorption experiment in the other study, could not remove the component in the actual landfill gas while it adsorbed well octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) in the LFG. Therefore the elimination of hexamethyldisiloxane is an important factor to determine the level of total organosilicon compound in pretreated landfill gas. Moreover, the L2 from the actual landfill gas was effectively adsorbed by the serial adsorption test using two columns packed with coconut activated carbon which has the great capacity of siloxanes removal among others. In order to utilize efficiently LFG as a renewable energy, the emission and adsorptive characteristics of the substance to be treated should be considered for the organization, operation, and management of pretreatment process.

Synthesis and Photopolymerization of Vinyl Ether and Epoxy-Functionalized Silicones

  • Pyun, Sang-Yong;Kim, Whan-Gi
    • Macromolecular Research
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    • v.11 no.3
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    • pp.202-205
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    • 2003
  • The reactive precursors, vinyl ethers, and epoxy-silicones, were synthesized. The vinyl ether monomers were prepared from primary alcohol and ethyl vinyl ether with mercury (II) acetate. The epoxy-functionalized silicones have been achieved by the controlled, rhodium-catalyzed, chemoselective hydrosilation of vinyl ether with siloxanes or silane. It was shown that the hydrosilation proceeds exclusively at the vinyl ether group of alkenyl vinyl ether without participation at the alkenyl group. The photoinduced cationic polymerization of these monomers was studied and found to be all highly reactive.

Organosiloxanes with molecular microrelief for liquid crystal alignment

  • Mazaeva, Vera G.;Belyaev, Victor V.;Timofeyev, Sergey N.;Min'ko, Anatoliy A.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.948-950
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    • 2009
  • A few organosilicon compounds (OC) - both cyclic and linear siloxanes with different structure of the substituents - have been synthesized. Properties of the LC anchoring on OC films have been measured. The OC investigated provide the homogeneous planar alignment with LC tilt angle in the range from $0.7^{\circ}$ to $1.9^{\circ}$. An increase of the microrelief depth results in a small increase of the tilt angle. The azimuthal anchoring is better for the films of the OC without molecular microrelief or the OC comprising polar groups.

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Syntheses and Properties of Copolymers of Tetramethyldisiloxane and 1,4-Bis(dimethylhydroxysilyl)benzene (Tetramethyldisiloxane-1,4-bis(dimethylhydroxysilyl)benzene 공중합체의 합성 및 특성)

  • Kim, Sun-ll;Yun, Young-Jae;Na, Jae-Woon
    • Applied Chemistry for Engineering
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    • v.7 no.3
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    • pp.490-495
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    • 1996
  • Low molecular weight linear chlorine terminated siloxanes (yields;71.2~86.5%) were prepared by reactions of cyclotri-, cyclotetra- and cyclopentasiloxane with dimethyldichlorosilane in the presence of pyridine N-oxide catalyst. The amine terminated siloxane oligomers were obtained in good yields(76.2~85.3%) by the reaction of linear chlorine terminated siloxanes with dimethylamine at $0^{\circ}C$. In this investigation, we have studied on the syntheses and properties of copolymers (yields;58.0~71.0%) obtained from the reaction of amine terminated siloxane oligomers with 1,4-bis(dimethylhydroxysilyl)benzene. The structures and properties of the copolymers were examined by FT-IR, $^1H$-NMR, TGA and DSC. Initial degradation temperatures($T_D{^i}$) of the polymer I and IV were confirmed as 476 and $485^{\circ}C$, respectively. The thermal stabilities of the polymers were found to be increased with increasing n of $(R_2SiO)_n$. The glass transition temperatures(Tg) of the polymers were increased with decreasing n of $(R_2SiO)_n$, and the lowest Tg revealed $-76^{\circ}C$ when n=5.

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Effect of Amino Modified Siloxanes with Two Different Molecular Weights on the Properties of Epoxy Composites for Adhesives for Micro Electronics (전자소재 접착제용 에폭시에 두 종의 다른 당량수를 갖는 아미노 변성 실록산이 미치는 영향)

  • Yu, Kihwan;Kim, Daeheum
    • Applied Chemistry for Engineering
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    • v.22 no.1
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    • pp.104-108
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    • 2011
  • In the non-conductive adhesives (NCAs) for adhesion of micro electro mechanical system (MEMS), there are some problems such as delamination and cracking resulting from the large differences of coefficients of thermal expansion (CTE) between NCAs and substrates. So, the addition of inorganic particles such as silica and nano clay to the CTEs composit have been applied to reduce the CTEs of the adhesives. Additions of the flexibilizers such as siloxanes have also been performed to improve the flexibility of epoxy composite. Amino modified siloxane (AMSs) were used to improve compatibility between epoxy and siloxane. In this study, glass transition temperatures (Tg) and moduli of those composites were measured to confirm the effects of AMS with two different equivalents on thermal/mechanical properties of AMS/epoxy composites. Tg of KF-8010/epoxy composites decreased from 148 to $122^{\circ}C$ and those of X-22-161A/epoxy composites decreased from 148 to $121^{\circ}C$. Moduli of KF-8010/epoxy composites decreased from 2648 to 2143 MPa by adding KF-8010 and moduli of X-22-161A/epoxy composites decreased from 2648 to 2014 MPa. In short, using long Si-O chain AMS leads to a greater decrease in moduli. However, haven't showed significant differences in Tg's.

Cyclic Co-oligomeric Ferroelectric Liquid Crystals with Fast Switching Properties, Wide SmC* Temperature Range and de Vries-type SmA*-SmC* Transition

  • Park, Seung-Beom;Cho, Tai-Yon;Yoon, Kyung-Hwan;Chang, Ji-Young;Zentel, Rudolf;Yoon, Do-Y.
    • Bulletin of the Korean Chemical Society
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    • v.32 no.spc8
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    • pp.3057-3062
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    • 2011
  • We have synthesized and characterized the first cyclic co-oligomeric ferroelectric liquid crystals (FLCs) based on cyclic siloxanes and found that the co-oligomer containing two different mesogenic units exhibits $SmC^*$ mesophase over a wide temperature range from $65^{\circ}C$ to $135^{\circ}C$, much wider than those of the monomer counterparts and the cyclic homo-oligomers. The cyclic co-oligomeric liquid crystal readily filled the display cell and exhibited fast switching times in the range of 4 ms to 6 ms over the entire $SmC^*$ phase. Moreover, the practical absence of layer shrinkage, attributed to de Vries-type transition, shows an additional significant advanage for cyclic co-oligomeric FLCs in LCD applications.