Showing papers on "Precipitated silica published in 2014"

SCC modification by use of amorphous nano-silica

Abstract: In this study two different types of nano-silica (nS) were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD), but produced through two different processes: fumed powder silica and precipitated silica in colloidal suspension. The influence of nano-silica on SCC was investigated with respect to the properties of concrete in fresh (workability) and hardened state (mechanical properties and durability). Additionally, the densification of the microstructure of the hardened concrete was verified by SEM and EDS analyses. The obtained results demonstrate that nano-silica efficiently used in SCC can improve its mechanical properties and durability. Considering the reactivity of the two applied nano-silicas, the colloidal type showed a higher reactivity at early age, which influenced the final SCC properties.

Influence of Silica Types on Synthesis and Performance of Amine–Silica Hybrid Materials Used for CO2 Capture

Abstract: Amine–silica hybrid materials have been investigated extensively in terms of their suitability for postcombustion CO2 capture. However, research on how the silica types affects the synthesis and performance of amine–silica hybrid materials is scarce. In this study, four types of commonly used and representative silica including precipitated silica, fumed silica, MCM-41, and silica gel are used to synthesize a series of comparable materials by grafting a silane onto them. We undertake a porosity analysis of plain silica and the amine–silica hybrid materials and determined the CO2 adsorption performance of amine–silica hybrid materials. The results suggest that precipitated silica is a superior and promising support material for amine–silica hybrid materials synthesis by grafting. The amine–silica hybrid material supporting with precipitated silica possesses relatively high amine content, exhibits good porosity, and obtains the highest CO2 adsorption capacity and amine efficiency compared to those of three ...

Thermal stability of styrene butadiene rubber (SBR) composites filled with kaolinite/silica hybrid filler

Abstract: Styrene butadiene rubber (SBR) composites filled with fillers, such as modified kaolinite (MK), precipitated silica (PS), and the hybrid fillers containing MK and PS, were prepared by melt blending. The kaolinite sheets were finely dispersed in the SBR matrix around 20–80 nm in thickness and reached the nano-scale. The SBR composites with fillers exhibited excellent thermal stability compared to the pure SBR. The thermal stability of SBR composites was improved with the increasing of MK mass fraction. When MK hybridized with PS, kaolinite sheets were covered by the fine silica particles and the interface between filler particles and rubber matrix became more indistinct. SBR composite filled by hybrid fillers containing 40 phr MK and 10 phr PS became more difficult in decomposition and was better than that of 50 phr PS/SBR and 50 phr MK/SBR in thermal stability. Therefore, the hybridization of the fine silica particles with the kaolinite particles can effectively improve the thermal stability of SBR composites.

Structure and property of polyvinyl alcohol/precipitated silica composite hydrogels for microorganism immobilization

Abstract: Polyvinyl alcohol (PVA) hydrogel filled with precipitated silica (PSi) was prepared by chemical crosslinking in the saturated boric acid solution. The structure and property of the composite hydrogel was studied. It was found that PSi could accelerate the crosslinking reaction of PVA, and the intermolecular bonding of PVA/PSi composite was confirmed. Effect of PSi on reactive kinetics of PVA hydrogel was investigated. The tensile strength of PVA hydrogel increased with PSi content. Proper content of PSi could also enhance the permeability and swelling property, resulting in the improvement of the capillary water absorption capacity of PVA hydrogel. By addition of PSi, many large pores formed in the hydrogel so as to provide channels for microbial metabolites. When being applied in waste water treatment, the value of oxygen uptake rate (OUR) and COD removal rate of the PVA composite hydrogel immobilized with activated sludge increased significantly, indicating that the microbial activity of PVA immobilized beads could be enhanced.

Effect of hybrid reinforcement based on precipitated silica and montmorillonite nanofillers on the mechanical properties of a silicone rubber

Abstract: Silicone rubber (SR) nanocomposites containing precipitated silica (PS), montmorillonite (MMT) and PS/MMT hybrid fillers were prepared through melt-mixing technique. In the SR/PS/MMT nanocomposite, the hybrid filler weight ratio was increased progressively from 0.4 to 1.7 while keeping the MMT weight constant. The viscosity, cure characteristics and mechanical properties of the nanocomposites were subsequently measured. The optimum cure time increased and the scorch time and rate of cure decreased. Furthermore, when the hybrid filler weight ratio was raised to its optimum, the tensile strength, Young’s modulus, modulus at 100% and 300% elongation (M100 and M300), elongation at break, stored energy density at break and hardness of the nanocomposite improved. The stress-strain properties of the nanocomposite with the hybrid filler improved at high deformation in comparison with those containing the PS and MMT fillers. The MMT filler exfoliated in the SR/MMT nanocomposite but did not in the nanocomposites containing the hybrid filler. Notably, the mechanical properties of the nanocomposite benefitted from the hybrid filler. This was due to the filler-filler and filler-rubber network formation in the rubber by the PS particles. Finally, effect of the PS, MMT and hybrid fillers on the energy loss or hysteresis of the rubber was measured.

Contribution of hydrogen and/or covalent bonds on reinforcement of natural rubber latex films with surface modified silica

Abstract: A macromolecular coupling agent containing hydrophilic and hydrophobic groups is made to react with precipitated silica. Interfacial interactions between OH groups of silica and COOH groups of macromolecule are found to be created through either hydrogen bonds alone or through hydrogen bonds and covalent bonds. Aqueous dispersions of unmodified and modified silica are prepared and the colloidal stability and particle size distribution of the dispersions are observed. The dispersions at neutral pH are incorporated into vulcanized/unvulcanized natural rubber latex. The formation of hydrogen bonds and/or covalent bonds is studied via FTIR spectroscopy and their contribution in encouraging filler-rubber interactions is emphasized through mechanical and swelling properties. Uniform distribution and dispersion of modified filler particles throughout the rubber matrix is confirmed by the microstructures of the latex films cast from filler added natural rubber latex. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40380.

On the Relation between Natural and Enforced Syneresis of Acidic Precipitated Silica

Abstract: Silica in industrial production processes is precipitated by mixing an acid and an inorganic precursor. In this aqueous solution, silica particles form due to a polymerization reaction and agglomeration and, finally, build a gel. Thereafter, the reaction continues, and the gel network shrinks with the expulsion of the enclosed pore liquid. This slow process is known as “natural syneresis” and strongly affects the product properties, such as the agglomerate size, specific surface or porosity of the silica produced. In order to investigate the influence of process parameters, such as temperature, pH or ionic strength, on the shrinkage in shorter time-scales, we propose an acceleration of this process and define it as “enforced syneresis”. The acceleration is performed by applying a mechanical external force to the gel by means of a plunger and measuring the shrinkage behavior under these conditions. Thereby, the conceptual idea is the prediction of the shrinkage due to natural syneresis based on the results of enforced syneresis. We are now able to predict the natural syneresis behavior from enforced syneresis data by the development of a correlative model. Using this prediction model, we can show the influence of temperature on the maximum shrinkage and on its rate in a significantly shorter time of about 12 h instead of several days.

Precipitated silica as filler for polymer electrolyte based on poly(acrylonitrile)/sulfolane

Abstract: The aim of the present work was to perform a preliminary study of the physicochemical properties of hybrid organic–inorganic gel electrolytes for Li-ion batteries based on the PAN/TMS - poly(acrylonitrile)/sulfolane - polymeric matrix and surface-modified precipitated silicas. Modifications were done by means of the so-called dry method using silane U-511 3-methacryloxypropyltrimetoxysilane. Scanning electron microscopy (SEM), noninvasive back scattering method (NIBS), specific surface area (BET), the degree of modification of the silica fillers—Fourier-transform infrared spectroscopy (FT-IR), impedance analysis, and charging/discharging were carried out. It is found that the silica fillers were homogeneously dispersed in the polymeric matrix, which enhanced conductivity and electrochemical stability of porous polymer electrolytes. Applicability of the prepared gel electrolytes for the Li-ion technology was estimated on the basis of specific conductivity measurements. It was shown that modification of the silica surface by the silane causes an increase in the gel-specific conductivity by about 2 orders of magnitude as compared to gel with unmodified silica.

The synthesis of novel zeolite Y nanoparticles using mesoporous silica with a temperature controlling method

Abstract: Porous nanoparticles aggregated from primary zeolite sodium-form Y (NaY) nanocrystals were hydrothermally synthesised using porous precipitated silica as the silica source via a three-stage temperature control strategy, using tetramethylammonium hydroxide (TMAOH) as an organic additive. The synthesised samples were characterised using powder X-ray diffraction, energy dispersive X-ray spectroscopy, nitrogen (N2) sorption, and particle size analysis. The results show that the zeolite aggregate particles with sizes of 150–600 nm were composed of highly crystalline zeolite NaY nanoparticles in the size range of 2–4 nm. The particle sizes of porous aggregates can be readily tuned by varying the additive amounts of the zeolite precursor gel without notably changing the sizes of the primary zeolite nanocrystals. The N2 sorption results show that the zeolite NaY aggregate particles had high microporosity with no clear mesoporosity. The zeolite particles exhibited very good resistance to mechanical conglomeration and remained intact after several months.

Properties of vulcanized polyisoprene rubber composites filled with opalized white tuff and precipitated silica.

Abstract: Opalized white tuff (OWT) with 40 μm average particle size and 39.3 m2/g specific surface area has been introduced into polyisoprene rubber (NR). Their reinforcing effects were evaluated by comparisons with those from precipitated silica (PSi). The cure characteristic, apparent activation energy of cross-link () and reversion (), and mechanical properties of a variety of composites based on these rubbers were studied. This was done using vulcanization techniques, mechanical testing, and scanning electron microscopy (SEM). The results showed that OWT can greatly improve the vulcanizing process by shortening the time of optimum cure (tc90) and the scorch time (ts2) of cross-linked rubber composites, which improves production efficiency and operational security. The rubber composites filled with 50 phr of OWT were found to have good mechanical and elastomeric properties. The tensile strengths of the NR/OWT composites are close to those of NR/PSi composites, but the tear strength and modulus are not as good as the corresponding properties of those containing precipitated silica. Morphology results revealed that the OWT is poorly dispersed in the rubber matrix. According to that, the lower interactions between OWT and polyisoprene rubber macromolecules are obtained, but similar mechanical properties of NR/OWT (100/50) rubber composites compared with NR/PSi (100/50) rubber composites are resulted.

Precipitated silica and paper industry/other applications thereof

Abstract: Precipitated silica specifically useful in the paper industry and in particular in paper-coating applications for inject printing, is characterized by an uptake of DOP oil lower than 260 ml/100 g, a pore volume (Vd25) of greater than 0.8 ml/g formed by pores having a diameter of less than 25 nm, a CTAB specific surface area of greater than 280 m2/g.

Reinforcement of natural rubber by precipitated silica: the influence of processing temperature

Abstract: The thermal history, and in particular the mixing dump temperature, is a parameter of paramount importance in mixing rubber and silica with a silane coupling agent in order to achieve proper silanization of silica and to avoid premature scorch reactions. The influence of the mixing dump temperature on the performance of silica-reinforced natural rubber (NR) is investigated. The investigation also includes the effect of nonrubber constituents, primarily proteins in NR, by using deproteinized natural rubber (DPNR) and synthetic polyisoprene (IR). The vulcanization properties and rubber-to-filler interactions of silica-reinforced NR in the presence and absence of a silane coupling agent are highlighted. With increasing mixing dump temperature, the silanization reaction between silica and silane coupling agent proceeds further. At a sufficiently high dump temperature, filler–filler interactions in the NR–silica compounds are reduced and the silica–rubber interaction improved, as evidenced by a drop in the Payne effect and increment in chemically bound rubber. It is demonstrated that NR and IR compounds mixed until they are above the optimum dump temperature exhibit cure reversion and reduction in tensile properties. On the other hand, DPNR–silica vulcanizates show slightly more constant physical properties.

Improving Flow Property of Nifedipine Loaded Solid-Lipid Nanoparticles by Means of Silica for Oral Solid Dosage Form

Abstract: In this study, a new formulation of silica nanocomposite containing nifedipine (NI) loaded freeze-dried solid-lipid nanoparticles (NI-SLNs) and silica have been developed with improved flowability of powders, which can lead to the formulation of a widely acceptable oral dosage form. The stable NI-SLNs were prepared using two phospholipids, hydrogenated soybean phosphatidylcholine and dipalmitoylphosphatidylglycerol mixed with 2.5% w/v trehalose as a cryoprotectant followed by lyophilization. We employed various grades of two types of silica, such as fumed and precipitated. Silica improved the poor flow property of NI-SLNs to good category as per USP-29. In addition, most of the silica nanocomposites showed the satisfactory results in their physicochemical properties such as particle size, polydispersity index, zeta potential, and recovered potency by around 100 nm, 0.3, -50 mV, and 80%, respectively. Furthermore, it was found that NI-SLNs were easily released form nanocomposites within 30 min, therefore, suggesting an improvement of drug dissolutions. Among them, precipitated silica cooperated fairly in improving the powder characteristics as well as the physicochemical, morphological, and pharmaceutical properties.

Organosilicon emulsion antifoaming agent and preparation method for same

Abstract: An organosilicon emulsion antifoaming agent and a preparation method for the same. Polyether-modified polysiloxanes are synthesized; an organosilicon composition is added to the polyether-modified polysiloxanes; the organosilicon composition is reacted with and combined with the polyether-modified polysiloxanes; and the combined product is emulsified by an emulsifier and is dispersed into particles with smaller particle size for improving the dispersibility of the organosilicon emulsion antifoaming agent in a washing agent. Additionally, precipitated silica with strong hydrophobicity is added to the mixture. The precipitated silica is not liable to be infiltrated by a surfactant in the washing agent and increases the quantity of defoaming particles and the density of the organosilicon emulsion antifoaming agent. With the precipitated silica, the organosilicon emulsion antifoaming agent suspends in the washing agent and does not precipitate out from the washing agent with the placing time being prolonged, and the degradation of the defoaming performance is effectively lleviated.

Effect of Epoxidation Level in Silica Filled Epoxidized Natural Rubber Compound on Cure, Rheological, Mechanical and Dynamic Properties

Abstract: Reinforcement of rubber by precipitated silica is adversely affected due to lack of strong polymer silica bonding. Functionalized polymers interact strongly with surface silanol groups of precipitated silica. In this work, effect of variation of epoxide content in silica filled Epoxidized Natural Rubber (ENR) compound was studied namely ENR 10, 25, 37.5 and 50mol%. Increasing in epoxide level of rubber has contributed to better rubber filler interaction and lead to better mechanical properties. Meanwhile, ENR’s with greater degree of polarity has contributed significantly to higher storage moduli at small deformation and also leads to increase in bound rubber content value. Fourier transform infrared spectroscopy studies showed that the silanol groups in silica interact with ENR through formation of Si-OH bond.

Sapphire substrate polishing solution for single-sided polishing machine

Abstract: The invention relates to a sapphire substrate polishing solution for a single-sided polishing machine. The sapphire substrate polishing solution is characterized by being especially applied to the single-sided polishing machine and relates to a preparation method for the sapphire substrate polishing solution for the single-sided polishing machine. The polishing solution contains silicon dioxide with different particle sizes. The polishing solution comprises silicon dioxide, an alkaline composition, an anionic surfactant and water. Silicon dioxide is colloidal silicon dioxide, fumed silica or precipitated silica. The alkaline composition is lithium hydroxide, potassium hydroxide, sodium hydroxide, aqueous ammonia, ethylene diamine, triethanolamine, and other organic alkalis. The anionic surfactant is at least one of a sulfonate surfactant, a carboxylate surfactant and a sulfate surfactant. According to the polishing characteristics of the single-sided polishing machine, by taking silica of different particle size specifications as abrasive material, the frictional resistance in polishing can be reduced and excellent lubrication effect can be achieved; the better polishing effect can be achieved while the polishing efficiency can be improved; and the production cost can be lowered.

Surface modification of silica with a hydrophilic polymer and its influence on reinforcement of natural rubber latex

Abstract: Surface modification of precipitated silica particles was carried out in both aqueous and non aqueous media separately with a polyacrylic based hydrophilic polymer synthesized in the laboratory. FTIR spectroscopy and thermo gravimetric analysis of the modified and unmodified silica particles were performed to confirm successful surface modification. Colloidal stability of the aqueous dispersions of the unmodified/modified silica particles were observed at different pH levels. The dispersions at neutral pH were incorporated in different proportions to un-compounded and compounded natural rubber latex (NRL) separately and thin latex films were produced from them by casting. Dispersability of silica particles within the rubber matrix was examined through microstructure studies of films cast from unmodified/modified silica incorporated un-compounded NRL. The influence of surface modification upon the reinforcement of NRL was investigated through tensile and tear strength properties of vulcanized NRL cast films containing modified silica. The uniform dispersion of silica particles and the improved mechanical properties envisaged better compatibility of modified silica particles with NRL by means of interfacial interactions. A significant improvement in the mechanical properties was observed in the films produced with 5 – 7 phr of modified silica. DOI: http://dx.doi.org/10.4038/jnsfsr.v42i4.7734 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 351-360

Plasterboards absorbing organic pollutants

Abstract: The invention relates to a plasterboard comprising a layer of plaster and at least one facing arranged on the latter, the layer of plaster comprising a microporous material and said microporous material comprising agglomerates of precipitated silica. This plasterboard has the property of effectively absorbing volatile organic compounds.

Turbo-charging rubber hose prepared from fluorine-containing silica gel

Abstract: The invention relates to a turbo-charging rubber hose prepared from fluorine-containing silica gel. Serving as an inner layer material for the turbo-charging rubber hose, the fluorine-containing silica gel comprises the following components in parts by weight: 20-30 parts of methyl vinyl silicone rubber, 35-45 parts of fluorine rubber premix rubber, 5-7 pars of fluorosilicone, 2-3 parts of hydroxyl silicone oil, 1.5-2 parts of peroxide vulcanizing agent 101-45S, 0.5-1 part of crosslinking agent TAIC (triallyl isocyanurate), 2-4 parts of precipitated silica, 10-15 parts of carbon black N990 and 5-10 parts of magnesium oxide. By using the excellent heat-resistant property and oil-resistant property of the fluorine-containing silica gel and the good adhesive property of the fluorine-containing silica gel with the silicone rubber, the turbo-charging rubber hose can meet the high heat-resistant property requirements, and meanwhile the problem that the turbo-charging rubber hose cannot meet the operating requirements after hot oil gas is mixed to cause the oil aging of the turbo-charging rubber hose, can be avoided.

Ultrafine Silica Additives Behavior during Alkali-Silica Reaction Long-Term Expansion Test

Abstract: A silica fume, precipitated silica, metakaolin and siliceous fly ash behavior as constituents of mortars was studied, while mortar samples have been tested for long-term alkali-silica reaction expansion in accordance to the GOST 8269.0 specification. Solid-state 29Si-MAS NMR spectroscopy and thermogravimetric analysis were used to describe Portland cement hydration, supplementary cementitious material pozzolanic reaction and to establish a structure of products of those processes. It was found that long-term test conditions, in contrast to the accelerated test, do not affect the composition of products formed too much, compared to normal conditions. This allows results obtained with long-term test to be expected as more relevant in terms of predicting of supplementary cementitious materials inhibiting properties.

Method for preparing transparent rubber reinforcing agent precipitated silica

Abstract: The invention discloses a method for preparing transparent rubber reinforcing agent precipitated silica. The method comprises the following steps: by adopting soluble sodium silicate as a raw material, obtaining dilute silicate after strongly acidic cation exchange; carrying out synthetic reaction under the condition of taking ammonium hydroxide as a precipitator and OP-10 as a surfactant to obtain silica; and obtaining a transparent rubber reinforcing agent precipitated silica product by the subsequent procedures of filter pressing, washing, spray drying, fluid energy milling, grading and packaging. The transparent rubber reinforcing agent precipitated silica prepared by the method is high in purity, and good in particle distribution, and a reinforcing agent with good transparency is provided for the transparent rubber product.

Composition of Scar Gel

Abstract: The present disclosure relates to a composition of scar gel. The composition of scar gel includes a silicone fluid, a volatile diluent, a precipitated silica powder, and an embellishing powder. The silicone fluid is fully miscible with the volatile diluent, and the precipitated silica powder and the embellishing powder are uniformly dispersed in the silicone fluid and the volatile diluent.

Use of a polycarboxylic acid in the production of an elastomer composition

Abstract: The invention relates to the use of a polycarboxylic acid in the production of an elastomer composition comprising a precipitated silica as a reinforcing inorganic load and an elastomer, wherein said polycarboxylic acid and said precipitated silica are incorporated, independently from each other, into an elastomer. The invention also relates to elastomer compositions and to the method for the production thereof.