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Firmed silica

The rheological properties of highly hydrophobic firmed silica HDK HI8 as outlined in this contribution can be readily explained by treating the pardcles as a composite material of a Si02 core... [Pg.906]

The remaining tetrachlorosilane is predominantly used for the production of firmed silica [20], which finds wide use in a variety of industrial applications. Most important are reinforcement of silicone elastomers as active filler and thickening of liquids as a rheological additive. A highly dispersed particle structure, high surface area and surface energy are the main characteristics of firmed silica. [Pg.476]

Typical fillers firmed silica, calcium carbonate, carbon black, silver, glass beads, metal powders, precipitated silica, aluminum oxide, montmorillonite. mica, zinc oxide... [Pg.698]

Typical concentration range firmed silica - 3-5 calcium carbonate - 20-50 wt%, glass beads - 5-20 wt%, aluminum oxide - 30-50 wt%. zinc oxide - up to 60%... [Pg.698]

Table 3. Properties of SAPO-31 samples synthesized with different reagents in n-octane hydroisomerization. Reference sample. All samples contained 1 % Pt. Reaction temperature - 340 °C. Cab-O-Sil - Cab-O-Sil M5 firmed silica. Silicic acid with sp. surface area of 1000 m /g, AS-40 - Ludox colloidal silica, TEOS -tetraethoxysilane. Sample with Reheis F2000 was synthesized with Cab-O-Sil. Table 3. Properties of SAPO-31 samples synthesized with different reagents in n-octane hydroisomerization. Reference sample. All samples contained 1 % Pt. Reaction temperature - 340 °C. Cab-O-Sil - Cab-O-Sil M5 firmed silica. Silicic acid with sp. surface area of 1000 m /g, AS-40 - Ludox colloidal silica, TEOS -tetraethoxysilane. Sample with Reheis F2000 was synthesized with Cab-O-Sil.
Changes in the apparent (bulk) density (Table 38.1, pap) do not correlate with S and Vp, which are mainly linked to the parameters of prunary particles and aggregates, but the empty space in firmed silica (Vemp (1000 - (pap/ PsiOjll/Pap) cormected to pap (i.e., agglomerates and... [Pg.507]

Cabot Corp., Untreated firmed silica general application guide. Technical Bulletin at www.cabot-corp.com. [Pg.404]

Besides its principal use mainly in coating/paint systems, firmed sflica may also be used in thermoplastics. Melt viscosity of poly(ethylene 2,6-naphthalate) (PEN) was reported to decrease with the employment of small amounts of firmed silica nanoparticles. Additional effects on mechanical properties and crystallization behavior by using untreated and surface-treated silica are reported in Ref. [33]. [Pg.419]

Typical fillers calcium carbonate, titanium dioxide, firmed silica, zinc oxide, carbon black, aluminum silicate, graphite, ceramic microspheres... [Pg.478]

Methods of filler pretreatment choice of carbon black for conductive applications is crucial because impurities on carbon black may have an adverse efleet on mechanical properties aluminum oxide and calcium carbonate were coated by a hydrophobic layer of PDMS heat treatment of firmed silica reduces its ability to reinforce polymer, especially in temperatures above 200T ... [Pg.570]

The hydrogel is allowed to stand for a few days during which time a process called sinerisis takes place. During sinerisis the condensation of the primary particles, one with another, continues and the gel shrinks further, accompanied by the elimination of more saline solution that exudes from the gel. After three or four days, sinerisis is complete and the gel becomes firm and can now be washed free of residual electrolytes with water. The washed product is finally heated to 120°C to complete the condensation of the surface silanol groups between the particles, and a hard xerogel is formed. It is this xerogel that is used as the LC stationary phase and for bonded phase synthesis. It is not intended to discuss the production of silica gel in detail and those interested are referred to "Silica Gel and Bonded Phases", published by Wiley (1). [Pg.57]

Water occurs in glass-ionomer and related cements in at least two different states (Wilson McLean, 1988 Prosser Wilson, 1979). These states have been classified as evaporable and non-evaporable, depending on whether the water can be removed by vacuum desiccation over silica gel or whether it remains firmly bound in the cement when subjected to such treatment (Wilson Crisp, 1975). The alternative descriptions loosely bound and tightly bound have also been applied to these different states of water combination. In the glass-poly(acrylic acid) system the evaporable water is up to 5 % by weight of the total cement, while the bound water is 18-28 % (Prosser Wilson, 1979). This amount of tightly bound water is equivalent to five or six molecules of water for each acid group and associated metal cation. Hence at least ten molecules of water are involved in the hydration of each coordinated metal ion at a carboxylate site. [Pg.49]

Virtually all current research in SFC utilizes either small bore packed columns with particles of 5-10 micrometers in diameter optimized for use in liquid chromatography or narrow bore, fused silica open tubular columns with Immobilized phases similar to those used in gas chromatography. In the latter case columns of saaller internal diameter, 10-100 micrometers, shorter lengths (generally less than 20 m with 1-10 m being the most common length), and more firmly crosslinked stationary phases are used by coaparison with standard columns for gas chromatography. In all... [Pg.819]

Fig. 3.5 Representation of a scheme of an experiment (upper set of drawings) and the obtained experimental results presented as AFM images (middle part) and cross-sectional profiles (bottom) that provides evidence of silica nucleation and shell formation on biopolymer macromolecules. Scheme of experiment. This includes the following main steps. 1. Protection of the mica surface against silica precipitation. It was covered with a fatty (ara-chidic) acid monolayer transferred from a water substrate with the Langmuir-Blodgett technique. This made the mica surface hydrophobic because of the orientation of the acid molecules with their hydrocarbon chains pointing outwards. 2. Adsorption of carbohydrate macromolecules. Hydrophobically modified cationic hydroxyethylcellulose was adsorbed from an aqueous solution. Hydrocarbon chains of polysaccharide served as anchors to fix the biomacromolecules firmly onto the acid monolayer. 3. Surface treatment by silica precursor. The mica covered with an acid mono-... Fig. 3.5 Representation of a scheme of an experiment (upper set of drawings) and the obtained experimental results presented as AFM images (middle part) and cross-sectional profiles (bottom) that provides evidence of silica nucleation and shell formation on biopolymer macromolecules. Scheme of experiment. This includes the following main steps. 1. Protection of the mica surface against silica precipitation. It was covered with a fatty (ara-chidic) acid monolayer transferred from a water substrate with the Langmuir-Blodgett technique. This made the mica surface hydrophobic because of the orientation of the acid molecules with their hydrocarbon chains pointing outwards. 2. Adsorption of carbohydrate macromolecules. Hydrophobically modified cationic hydroxyethylcellulose was adsorbed from an aqueous solution. Hydrocarbon chains of polysaccharide served as anchors to fix the biomacromolecules firmly onto the acid monolayer. 3. Surface treatment by silica precursor. The mica covered with an acid mono-...
Triflic acid has also been supported on a porous silica carrier (220). The authors emphasized the importance of a strong interaction between the acid and the support to prevent leaching of the acid. In pulsed liquid-phase isobutane/ 1-butene alkylation experiments at 298 K, the catalysts produced a very high-quality alkylate, made up almost exclusively of isooctanes. With silanol groups on the silica surface or with added water, triflic acid was found to form a monohydrate that was firmly grafted to the silica surface. [Pg.293]

Dispersion of POMs onto inert solid supports with high surface areas is very important for catalytic application because the surface areas of unsupported POMs are usually very low (—10 m2g). Another advantage of dispersion of POMs onto inert supports is improvement of the stability. Therefore, immobilization of POMs on a number of supports has been extensively studied. Silica and active carbon are the representative supports [25], Basic supports such as MgO tend to decompose POMs [101-104], Certain kinds of active carbons firmly entrap POMs [105,106], The maximum loading level of POMs on active carbons is 14 wt% [107], Dispersion of POMs onto other supports such as zeolites, mesoporous molecular sieves, and apatites, is of considerable interest because of their high surface areas, unique pore systems, and possibility to modify their compositions, morphologies, and sorption properties. However, a simple impregnation of POM compounds on inert supports often results in leaching of POMs. [Pg.475]

Liquid chromatographic clean up [441,443,450] has been used either in normal phase flow using alumina, silica, or florisil [22,189,403,481,484] or with reverse-phase (RP) columns [409,452,480]. In most cases these techniques are well established and are used in an off-line mode, primarily to remove the bulk of co-extracted materials prior to a more refined clean-up prior to the final determination. These columns may be prepared in the laboratory [22,403 -405] or commercial solid phase extraction (SPE) cartridges can be used [409,452, 463,470,485,486]. In both cases, the normal phase cartridges and column materials are disposable since many of the polar co-extractants bind firmly to the substrate surface and are difficult to remove. This has been overcome to some... [Pg.66]

On silica, infrared spectra 146, 141 > 161) have shown clearly that two general sites of adsorption exist. Type I comprises the OH sites that remain firmly bound to the surface even after long times of evacuation at 450° C., and the other (type II) is the oxygen (or possibly the silicon) atoms in the surface. It is probable that the surface of most oxides consists of oxygen, but little is known in detail about this. Models of the arrangement of the OH groups have been suggested 152,153). [Pg.303]

QUARTZITE. A hard, tough, and compact metamorphic rock composed almost wholly of quartz sand grains that have been reciystallized to form a particularly massive siliceous rock. The term is also used for non-metamorphosed quartzose sandstones and grits whose clastic grains have been firmly cemented by silica lhat has grown in optical continuity around each grain. [Pg.1398]

Fill the sinter to the lip with Silica gel 60 (400-230 mesh), and apply suction pressing the silica with extra care at the circumference. Still pressing, level the surface, tapping the sides of the sinter firmly to obtain a totally level surface and a head space for the addition of solvents. [Pg.220]


See other pages where Firmed silica is mentioned: [Pg.339]    [Pg.275]    [Pg.776]    [Pg.154]    [Pg.107]    [Pg.184]    [Pg.129]    [Pg.151]    [Pg.887]    [Pg.257]    [Pg.339]    [Pg.275]    [Pg.776]    [Pg.154]    [Pg.107]    [Pg.184]    [Pg.129]    [Pg.151]    [Pg.887]    [Pg.257]    [Pg.13]    [Pg.733]    [Pg.168]    [Pg.254]    [Pg.540]    [Pg.291]    [Pg.4]    [Pg.500]    [Pg.718]    [Pg.214]    [Pg.228]    [Pg.21]    [Pg.39]    [Pg.103]    [Pg.185]    [Pg.38]    [Pg.48]    [Pg.154]    [Pg.232]   
See also in sourсe #XX -- [ Pg.875 , Pg.882 , Pg.902 ]




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