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Colloidal Silica (colloidal + silica)
Terms modified by Colloidal Silica Selected AbstractsSynthesis and characterization of hybrid nanocomposites comprising poly(vinyl alcohol) and colloidal silicaADVANCES IN POLYMER TECHNOLOGY, Issue 3 2008Mousumi De Sarkar Abstract Organic,inorganic hybrid composite films were developed using poly(vinyl alcohol) (PVA) and an aqueous dispersion of colloidal silica of initial particle size of 15,30 nm. The hybrid films, prepared with varied proportion of colloidal silica (10,90 phr), were found to be transparent, indicating the nanolevel dispersion of the inorganic component over the polymer. Morphological studies further revealed no significant agglomeration of the silica domains embedded into the polymer matrix. A depression in glass transition temperature of PVA is observed with increasing proportion of silica. The degree of crystallinity also showed a decreasing trend with increasing amount of silica. However, the composite films demonstrated superior mechanical performances, higher resistances to dissolution in boiling water, and lower permeability compared with virgin PVA, owing to the better interaction between PVA and silica as well as the reinforcing action of nanosilica particles in the polymer matrix. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:152,162, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20129 [source] Multilevel structure of reinforcing silica and carbonJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000D.W. Schaefer Using small-angle x-ray (SAXS), neutron (SANS), x-ray diffraction and light scattering, we study the structure of colloidal silica and carbon on length scales from 4 Ĺ < q,1 < 107 Ĺ where q is the magnitude of the scattering vector. These materials consist of primary particles of the order of 100 Ĺ, aggregated into micron-sized aggregates that in turn are agglomerated into 100 µ agglomerates. The diffraction data show that the primary particles in precipitated silica are composed of highly defective amorphous silica with little intermediate-range order (order on the scale of several bond distances). On the next level of morphology, primary particles arise by a complex nucleation process in which primordial nuclei briefly aggregate into rough particles that subsequently smooth out to become the seeds for the primaries. The primaries aggregate to strongly bonded clusters by a complex process involving kinetic growth, mechanical disintegration and restructuring. Finally, the small-angle scattering (SAS) data lead us to postulate that the aggregates cluster into porous, rough-surfaced, non-mass-fractal agglomerates that can be broken down to the more strongly bonded aggregates by application of shear. We find similar structure in pelletized carbon blacks. In this case we show a linear scaling relation between the primary and aggregate sizes. We attribute the scaling to mechanical processing that deforms the fractal aggregates down to the maximum size able to withstand the compaction stress. Finally, we rationalize the observed structure based on empirical optimization by filler suppliers and some recent theoretical ideas due to Witten, Rubenstein and Colby. [source] Synthesis of organic,inorganic hybrid polymeric nanocomposites for the hard coat applicationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Chuan Hsiao Shu Abstract An organic,inorganic hybrid polymeric nanocomposite has been synthesized for making UV-curable hard coats. This nanocomposite consists of nano-sized colloidal silica functionalized with vinyltriethoxysilane (VTES) and dendritic acrylic oligomers (DAO) which have been formed earlier via a reaction of ethylenediamine (EDA) with trimethylopropane triacrylate (TMPTA). Applied as a hard coat on top of a polyethylene terephthalate (PET) film, this nanocomposite has a short UV-cure time and the cured coat has an enhanced thermal decomposition temperature (Td), 89,90% transparency, increased hardness up to 3H, better adhesion up to 4B, and a flat surface with a root mean square roughness of 2,4 nm. The preparation as well as the characterization of the constituting species and the final hybrid are described in detail. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3985,3993, 2007 [source] Evaluation of a new fiber-reinforced resin compositeJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006S. Suzuki Abstract Efficacy of the usage of an experimental fiber-reinforced composite (FRC) on mechanical properties of an indirect composite was investigated by means of three-point bending and Charpy impact tests. Bond strength between the FRC and the indirect composite was also evaluated by tensile testing. The FRC consisted of a matrix resin with 25% silanized milled glass fiber (11-,m diameter, 150-,m length) and 5% colloidal silica. The values of strain of proportional limit, total strain, and fracture energy of the FRC during the bending test (1.2%, 10.4%, and 41.6 × 10,3 J) were significantly higher than those of the indirect composite (0.1%, 2.5%, and 11.9 × 10,3 J). The impact strengths of the 1-mm specimens with FRC ranged from 15.2 to 15.9 kJ/m2, and were significantly higher than that of the control (3.1 kJ/m2). The 2-mm specimens showed significant difference from the control when the FRC thickness was equal or greater than 0.5 mm. The bond strength after the thermocycling was 15.2 MPa, and all of the specimens exhibited cohesive fracture inside the indirect composite. Based upon the results, it was concluded that the FRC tested in this study improved toughness and impact resistance of the indirect composite. The interfacial bonding between the FRC and the indirect composite was strong enough to prevent delamination. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Templating synthesis of non-spherical polymer particles and their effect on the fracture toughness of an epoxy-amine networkPOLYMER INTERNATIONAL, Issue 1 2007Zhongjie Du Abstract Flexible non-spherical polymer particles were successfully produced via concentrated emulsion polymerization. LUDOX TM-50 (colloidal silica, 50 wt% suspension in water) was introduced into the continuous phase to strengthen the template and inhibit monomer diffusion between the continuous and dispersed phases. The extent of non-spherical shape was identified by the roundness value. Transmission electron micrographs showed that the higher the volume fraction of the dispersed phase became, the more non-spherical were the poly(butyl acrylate) (PBA) particles. As an application, the effect of the non-spherical particles on the fracture toughness of a modified epoxy-amine network was studied. Scanning electron micrographs showed that the introduction of the non-spherical PBA particles improved efficiently the impact strength of the cured epoxy resin. Copyright © 2006 Society of Chemical Industry [source] Plasma phospholipids implicated in the matrix effect observed in liquid chromatography/tandem mass spectrometry bioanalysis: evaluation of the use of colloidal silica in combination with divalent or trivalent cations for the selective removal of phospholipids from plasmaRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2008Steven T. Wu The feasibility of the use of colloidal silica in combination with a number of divalent or trivalent cations for the removal of plasma phospholipids was evaluated by sequentially adding the two reagents (i.e., colloidal silica and a cation) directly to blank plasma samples or plasma samples spiked with analytes. Three representative plasma phospholipids were monitored to determine the efficiency of the phospholipids removal under different reagent combinations. The recovery of each spiked analyte was also monitored under each condition in order to determine if any of the analyte was removed along with the phospholipids. By optimizing the amounts of the reagents used and the sequence of the addition of the reagents, quantitative and reproducible removal of the phospholipids was achieved. Using the finally selected lanthanum cation, the removal of phospholipids was achieved with minimal concomitant loss of the ten investigated analytes which were carefully selected to incorporate functional groups that could potentially interact with the added reagents and hence could be removed along with the phospholipids. Copyright © 2008 John Wiley & Sons, Ltd. [source] TEOS,colloidal silica,PDMS-OH hybrid formulation used for stone consolidationAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Carmen Salazar-Hernández Abstract The consolidation of materials concept, which consists of introducing a chemical substance (consolidant) into degraded stone, has been applied to architectural conservation. Silicon compounds such as tetraethoxysilane (TEOS) are frequently used as a base for commercial consolidant formulations due to their ability to form a siloxane polymer such as SiO2. However, the silica xerogels deposited into the stone show poor performance and the gels obtained are non-porous and tend to crack during the drying stage. In order to avoid the fractures and to improve gel properties, we propose the synthesis of a hybrid consolidant based on TEOS and fillers such as colloidal silica (200 nm in diameter) and hydroxy-terminated polydimethylsiloxane (PDMS-OH). Both additives enhance gel properties such as porosity and elasticity, leading to the formation of non-fractured and permeable gels. Characterization of the hybrid xerogel was carried out by nitrogen adsorption and 29Si MAS-NMR. The properties of the hybrid xerogels were compared with those prepared from a formulation based on TEOS (T-ME) with a composition similar to a commercial product. In order to evaluate the effectiveness of the hybrid consolidant, it was applied to tuff-stone of historical monuments in the city of Guanajuato, Mexico. The tuff-stone was also treated with the formulation T-ME. Both treatments were studied by determining the percentage of consolidant deposited, evaluating changes in porosity and hardness of the treated stone. The applicability of the hybrid consolidant for the decayed tuff-stone is under study. Copyright © 2010 John Wiley & Sons, Ltd. [source] | |||||||||||||