• Title/Summary/Keyword: silica

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Properties of Silica-SBR Compounds Using Cellulose Dispersant Applicable to Tire Tread Rubber

  • Kim, Jung Soo;Kim, Dong Hyun
    • Elastomers and Composites
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    • v.55 no.3
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    • pp.176-183
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    • 2020
  • Silica-styrene butadiene rubber (Silica-SBR) compounds have been used in the preparation of tire treads. The silica dispersibility of silica-SBR compounds is related to the processability, mechanical properties, and wear resistance of tires. Recently, in order to improve the silica dispersibility of the silica-SBR compounds, the wet masterbatch (WMB) process was introduced, which is a method of mixing rubber in the water phase. We aimed to improve the silica dispersibility of the silica-SBR compounds by preparing a silica dispersant applicable to the WMB process. For this purpose, cellulose, 2-hydroxyethyl cellulose, and cellulose acetate were employed as a silica dispersant. The silica dispersibility of the compounds was measured by a moving die rheometer. Improvement in the processability of silica-SBR compounds was evaluated by the Mooney viscometer. The wear resistance of silica-SBR compounds using a cellulose dispersant was improved by up to 29%.

Reinforcing Performance of Networked Silicas in Silica-filled Chloroprene Rubber Compounds

  • Ryu, Changseok;Yang, Jae-Kyoung;Park, Wonhyeong;Kim, Sun Jung;Kim, Doil;Seo, Gon;Kim, Wook-Soo;Ahn, Ki Woong;Kim, Beak Hwan
    • Elastomers and Composites
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    • v.54 no.1
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    • pp.40-53
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    • 2019
  • The physical properties of chloroprene rubber (CR) compounds reinforced with networked silicas were investigated by comparing them to those reinforced with conventional silica to observe the effect of the organic connection bonds combining silica particles on their cure, tensile, and aging performance. The introduction of networked silica to CR increase in silica content to 80 phr in rubber, while the content of conventional silica was limited to 60 phr. The CR compounds reinforced with networked silica showed higher resistance to combustion. The gradual increases in delta torque, Mooney viscosity, and modulus of silica-filled CR compounds with silica content were mainly attributed to the specific interaction between the chlorine atoms of CR and the hydroxyl groups of silica. The CR compounds reinforced with networked silica showed low compression set and heat build-up and maintained their high modulus even after thermal, oil, and ozone aging.

Effect of Silica Content on the Dielectric Properties of Epoxy/Crystalline Silica Composites

  • Park, Jae-Jun
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.6
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    • pp.322-325
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    • 2012
  • Crystalline silica was synthesized by annealing amorphous silica at $1,300^{\circ}C$ or $1,400^{\circ}C$ for various times, and the crystallinity was estimated by X-ray diffraction (XRD) analysis. In order to prepare a low dielectric material, epoxy/crystalline silica composites were prepared, and the effect of silica content on the dielectric properties was studied under various functions of frequency and ambient temperature. The dielectric constant decreased with increasing crystalline silica content in the epoxy composites, and it also decreased with increasing frequency. At 120 Hz, the value of 5 wt% silica decreased by 0.25 compared to that of 40 wt% silica, and at 23 kHz, the value of 5 wt% silica decreased by 0.23 compared to that of 40 wt% silica. The value increased with increasing ambient temperature.

In-Situ Synthesis of PS/(-)Silica Composite Particles in Dispersion Polymerization Using An ($\pm$) Amphoteric Initiator

  • Hwang, Deok-Ryul;Hong, Jin-Ho;Lee, Jeong-Woo;Shim, Sang-Eun
    • Macromolecular Research
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    • v.16 no.4
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    • pp.329-336
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    • 2008
  • Core/shell ($\pm$)PS/(-)silica nanocomposite particles were synthesized by dispersion polymerization using an amphoteric initiator, 2,2'-azobis [N-(2-carboxyethyl)-2,2-methylpropionamidine] ($HOOC(CH_2)_2HN$(HN=) $C(CH_3)_2CN$=NC $(CH_3)_2C$(=NH)NH $(CH_2)_2COOH$), VA-057. Negatively charged (-6.9 mV) silica was used as the stabilizer. The effects of silica addition time and silica and initiator concentrations were investigated in terms of polymerization kinetics, ultimate particle morphology, and size/size distribution. Uniform hybrid microspheres with a well-defined, core-shell structure were obtained at the following conditions: silica content = 10-15 wt% to styrene, VA-057 content=above 2 wt% to styrene and silica addition time=0 min after initiation. The delay in silica addition time retarded the polymerization kinetics and broadened the particle size distribution. The rate of polymerization was strongly affected by the silica content: it increased up to 15 wt% silica but then decreased with further increase in silica content. However, the particle size was only marginally influenced by the silica content. The zeta potential of the composite particles slightly decreased with increasing silica content. With increasing VA-057 concentration, the PS microspheres were entirely coated with silica sol above 1.0 wt% initiator.

Protein-silica Interaction in Silica-based Gel Filtration Chromatography (Silica-based Gel Filtration 크로마토그래피에서의 단백질-실리카 상호작용)

  • Choi, Jung-Kap;Yoo, Gyurng-Soo
    • YAKHAK HOEJI
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    • v.35 no.6
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    • pp.461-465
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    • 1991
  • Silica-based gel filtration chromatography has been used to characterize molecular weight of proteins. However, the molecular weight measured by this method was distorted by protein-silica interactions like hydrophobic and electrostatic forces. Therefore, we characterized protein-silica interaction using two forms of phytochrome (124 kDa) having different hydrophobicity and surface charge. PH and ionic strength affected the retention time of phytochrome suggesting that electrostatic force is the major interaction between protein and silica surface.

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LED Driver Solution for Backlighting large TFT-LCD Panels with Adaptive Power Control & Video Synchronization

  • Dhayagude, Tushar;Dilip, S;Santo, Hendrik;Vi, Kien;Chen, Sean;Kim, Min-Jong;Schindler, Matt;Ghoman, Ran
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1487-1490
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    • 2008
  • mSilica developed a scalable integrated circuit solution for driving multiple arrays of LEDs to backlight TFT-LCD panels. The drivers incorporate adaptive power control of the DC-DC power supply powering the LEDs to improve the efficiency while synchronizing PWM dimming with video timing signals VSYNC and HSYNC to reduce motion blur.

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Porous Silica Particles As Chromatographic Separation Media: A Review

  • Cheong, Won Jo
    • Bulletin of the Korean Chemical Society
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    • v.35 no.12
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    • pp.3465-3474
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    • 2014
  • Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-$3{\mu}m$ silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.

Separation of Hydrogen-Nitrogen Gas Mixture by PTMSP-Silica-PEI Composite Membranes (PTMSP-Silica-PEI 복합막에 의한 수소-질소 혼합기체 분리)

  • Lee Hyun-Kyung;Choi Youn-Jung
    • Membrane Journal
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    • v.14 no.4
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    • pp.304-311
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    • 2004
  • The poly(1-trimethylsilyl-1-propyne) (PTMSP) and silica-filled PTMSP membranes were prepared by casting from a toluene solution on porous polyetherimide (PEI). FT-IR spectrum, GPC and SEM pictures have been taken to characterize the membranes. The particle size of membrane decreases as silica content of the membrane increases from 23 to 60 wt%, and a uniform distribution of the silica is observed. The separation properties of the gas mixture (32 mol% $H_2$/ 68 mol% $N_2$) through the composite membranes were studies as a function of pressure and percentage of silica. Selectivity values of $H_2$/$N_2$ increased as the pressure of permeation cell and silica content of the membrane increased. The real separation factor($\alpha$), head separation factor($\beta$), and tail separation factor((equation omitted)) of PTMSP-PEI composite membrane were 2.28, 1.58, and 1.44 respectively at $\Delta$P 30 psi and $25^{\circ}C$. $\alpha$, $\beta$, and (equation omitted) of PTMSP-Silica-PEI composite membrane for 60 wt% silica were 3.34, 1.95, 1.72 at $\Delta$P 30 psi and $25^{\circ}C$.

Preparation of Silica-Filled SBR Compounds with Low Rolling Resistance by Wet Masterbatch

  • Yang, Jae-Kyoung;Park, Wonhyeong;Ryu, Changseok;Kim, Sun Jung;Kim, Doil;Seo, Gon
    • Elastomers and Composites
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    • v.55 no.1
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    • pp.26-39
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    • 2020
  • The physical properties of silica-filled SBR compounds (WSBR) prepared using silica-SBR wet masterbatches (WMB) were systematically investigated to understand the effect of the surface treatment of silica on the reinforcement performance of SBR. Treatment of silica with bis(triethoxysilylpropyl)tetrasulfide (TESPT) in the liquid phase, followed by mixing with an SBR solution and recovery by water stripping, easily produced silica-SBR WMB. However, insufficient surface treatment in terms of the amount and stability of the incorporated TESPT led to considerable silica loss and inevitable TESPT elution. Pretreatment of silica in the gas phase with TESPT and another organic material that enabled the formation of organic networks among the silica particles on the surface provided hydrophobated silica, which could be used to produce silica-SBR WMB, in high yields of above 99%. The amount and type of organic material incorporated into silica greatly influenced the cure characteristics, processability, and tensile and dynamic properties of the WSBR compounds. The TESPT and organic material stably incorporated into silica increased their viscosity, while the organic networks dispersed on the silica surface were highly beneficial for reducing their rolling resistance. Excessive dosing of TESTP induced low viscosity and a high modulus. The presence of connection bonds formed by the reaction of glycidyloxy groups with amine groups on the silica surface resulted in physical entanglement of the rubber chains with the bonds in the WSBR compounds, leading to low rolling resistance without sacrificing the mechanical properties. Mixing of the hydrophobated silica with a rubber solution in the liquid phase improved the silica dispersion of WSBR compounds, as confirmed by their low Payne effect, and preservation of the low modulus enhanced the degree of entanglement.

The Effect of pH on Synthesis of Nano-Silica Using Water Glass (물유리를 이용한 나노실리카 제조 시 pH가 미치는 영향)

  • Choi, Jin Seok;An, Sung Jin
    • Korean Journal of Materials Research
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    • v.25 no.4
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    • pp.209-213
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    • 2015
  • Synthesis of nano-silica using water glass in a Sol-Gel process is one of several methods to manufacture nano-silica. In nano-silica synthesized from water glass, there are various metal impurities. However, synthesis of nano-silica using water glass in a Sol-Gel process is an interesting method because it is relatively simple and cheap. In this study, nano-silica was synthesized from water glass; we investigated the effect of pH on the synthesis of nano-silica. The morphology of the nanosilica with pH 2 was flat, but the surface of the nano-silica with pH 10 had holes similar to small craters. As a result of ICP-OES analysis, the amount of Na in the nano-silica with pH 2 was found to be 170 mg/kg. On the other hand, the amount of Na in the nano-silica with pH 10 was found to be 56,930 mg/kg. After calcination, the crystal structure of the nano-silica with pH 2 was amorphous. The crystal structure of the nano-silica with pH 10 transformed from amorphous to tridymite. This is because elemental Na in the nano-silica had the effect of decreasing the phase transformation temperature.