Showing papers on "Precipitated silica published in 2016"

Silica–Epoxy Vitrimer Nanocomposites

Abstract: Reinforced silica–epoxy vitrimer nanocomposites have been made in a solvent-free, easily processable, and economical way with filler contents up to 40 wt %. Increasing silica content leads to higher modulus materials in both glassy and rubbery regions. These nanocomposites are insoluble like permanent cross-linked networks but can completely relax stresses by thermoactivated exchange reactions that rearrange the network topology. Furthermore, the surface functionalization of particles improves the dispersion of fillers and accelerates the relaxation process. Similar results were obtained with industrial precipitated silica, which would allow vitrimer nanocomposites to be produced on an industrial scale.

Colloidal Silica Particle Synthesis and Future Industrial Manufacturing Pathways: A Review

Abstract: Colloidal silica is used in many applications including catalysis, pharmaceuticals, and coatings. Although naturally formed silica materials are widely available, they are often in forms that are difficult to process or are even harmful to health. Therefore, uniform colloidal silicas are generally manufactured using synthetic chemical processes. While established high temperature gaseous synthesis methods fall out of favor in our energy conscious society, liquid synthesis methods are current industrial leaders. The precipitated silica method provides the majority share of commercially produced specialty silicas with its economic advantages predicted to continue to grow in the future. The biomimetic method and microemulsion methods of synthesis provide a superior level of surface chemistry and morphological control than current industrial processes and are the major focus of current silica synthesis research. Movement toward more tailor-made products and ecologically friendly production methods will likely...

Cytotoxic and genotoxic evaluation of different synthetic amorphous silica nanomaterials in the V79 cell line.

Abstract: The nature of occupational risks and hazards in industries that produce or use synthetic amorphous silica (SAS) nanoparticles is still under discussion. Manufactured SAS occur in amorphous form and can be divided into two main types according to the production process, namely, pyrogenic silica (powder) and precipitated silica (powder, gel or colloid). The physical and chemical properties of SAS may vary in terms of particle size, surface area, agglomeration state or purity, and differences in their toxicity potential might therefore be expected. The aim of this study was to compare the cytotoxicity and genotoxicity of representative manufactured SAS samples in Chinese hamster lung fibroblasts (V79 cells). Five samples from industrial SAS producers were evaluated, that is, two pyrogenic SAS powders (with primary particle sizes of 20 nm and 25/70 nm), one precipitated SAS powder (20 nm) and two precipitated SAS colloids (15 and 40/80 nm). V79 cell cultures were treated with different concentrations of SAS pre-dispersed in bovine serum albumin -water medium. Pyr (pyrogenic) 20, Pre (precipitated) 20 and Col (colloid) 15 significantly decreased the cell viability after 24 h of exposure, whilst Pyr 25/70 and Col 40/80 had negligible effects. The cytotoxicity of Pyr 20, Pre 20 and Col 15 was revealed by the induction of apoptosis, and Pyr 20 and Col 15 also produced DNA damage. However, none of the SAS samples generated intracellular reactive oxidative species, micronuclei or genomic mutations in V79 cells after 24 h of exposure. Overall, the results of this study show that pyrogenic, precipitated and colloidal manufactured SAS of around 20 nm primary particle size can produce significant cytotoxic and genotoxic effects in V79 cells. In contrast, the coarser-grained pyrogenic and colloid SAS (approximately 50 nm) yielded negligible toxicity, despite having been manufactured by same processes as their finer-grained equivalents. To explain these differences, the influence of particle agglomeration and oxidative species formation is discussed.

Preparation and Characterization of Silica Material from Rice Husk Ash – An Economically Viable Method

Abstract: Rice husk is a form of agricultural biomass that provides an abundant silicon source. Rice husks are widely burnt in agricultural fields in India because it is difficult to find other uses for them. Farmers burn rice hulls usually under incomplete combustion conditions to avoid accidental fires. The objective of this study was to develop a new method of amorphous silica was prepared from rice husk ash by sol - gel method. Initially received from Rice husk ash was calcined at 400 0 C, 500 0 C, 600 0 C and 700 0 C for 5 hrs to remove the volatiles in the sample and determine the amorphous structure of SiO 2 . Next, the thermally treated RHA was mixed with alkali solution to produce sodium silicate solution and precipitated silica was produced by the neutralization of sodium silicate solution. Rice Husks soaked in nitric acid produced the maximum amount of the sodium silicate solution and precipitated silica. Sodium oxide (Na 2 O) content and silica (SiO 2 ) content in the sodium silicate solution were also determined. Extracted precipitated silica particles were characterized by Fourier transform infrared (FTIR), X-Ray diffraction and Optical microscopy techniques. The chemical composition of silica was confirmed by FTIR and SEM with EDX.. Highly pure amorphous silica was derived from rice husk ash was confirmed by XRD pattern. The morphology of the obtained materials was analyzed by SEM. At optimized conditions, a nano sized highly pure silica was produced with a high reactivity and 99.9% amorphous in form. This economic technology as applied to waste material also provides many benefits to the local agro industry. Thus this paper may be providing a low cost and simple method to prepare functional materials. Keywords : Rice husk ash, Silica gel, Minerals, Amorphous material, Agricultural bio-waste

Physicochemical and toxicological evaluation of silica nanoparticles suitable for food and consumer products collected by following the EC recommendation

Abstract: Specific information about the particle size distribution, agglomeration state, morphology, and chemical composition of four silica samples, used as additives in food and in personal care products, were achieved with a combination of analytical techniques. The combined use of differential centrifugal sedimentation (DCS), sedimentation field flow fractionation (SdFFF), and scanning and transmission electron microscopy (SEM and TEM) allows to classify the water dispersed samples as “nanomaterials” according to the EC definition. The mechanical stirring and the ultrasound treatment were compared as dispersion methods. The particle surface chemical composition, determined by particle-induced X-ray emission (PIXE) and X-ray photoelectron spectroscopy (XPS), assessed the different levels of purity between the pyrogenic and the precipitated silica and highlighted particle surface chemical composition modifications in the outer shell when dispersed by mechanical stirring. The potential toxic effects of silica on intestinal Caco-2 cells were investigated using MTS assay and by measuring lactate dehydrogenase (LDH) release and caspases 3/7 activity after 24 h of incubation. No or limited decrease of cell viability was observed for all particles regardless of dispersion procedure, suggesting a relative innocuity of these silica samples.

Plasticity, strength, permeability and compressibility characteristics of black cotton soil stabilized with precipitated silica

Abstract: The suitability of using precipitated silica (PS) from the burning of rice husk was investigated to improve the geotechnical engineering properties of a black cotton soil. A laboratory experimental program consisting of series of specific gravity, Atterberg limits, compaction, California bearing ratio (CBR), unconfined compression and consolidation tests was conducted on the untreated and PS treated soil samples. The application of PS to the soil significantly changed its properties by reducing its plasticity and making it more workable, improving its soaked strength, and increasing its permeability and the rate at which the soil gets consolidated. An optimal PS content of 50%, which provided the highest soaked strength, is recommended for the improvement of the subgrade characteristics of the BC soil for use as a pavement layer material.

Reinforcement of multiwalled carbon nanotube in nitrile rubber: in comparison with carbon black, conductive carbon black, and precipitated silica

Abstract: The properties of nitrile rubber (NBR) reinforced by multiwalled carbon nanotube (MWCNT), conductive carbon black (CCB), carbon black (CB), and precipitated silica (PSi) were investigated via viscoelastic behavior, bound rubber content, electrical properties, cross-link density, and mechanical properties. The filler content was varied from 0 to 15 phr. MWCNT shows the greatest magnitude of reinforcement considered in terms of tensile strength, modulus, hardness, and abrasion resistance followed by CCB, CB, and PSi. The MWCNT filled system also exhibits extremely high levels of filler network and trapped rubber even at relatively low loading (5 phr) leading to high electrical properties and poor dynamic mechanical properties. Although CCB possesses the highest specific surface area, it gives lower level of filler network than MWCNT and also gives the highest elongation at break among all fillers. Both CB and PSi show comparable degree of reinforcement which is considerably lower than CCB and MWCNT.

AC corona resistance performance of silicone rubber composites with micro/nano silica fillers

Abstract: Silicone rubber (SR) insulating surfaces are often subjected to corona partial discharges (PD) during outdoor operation which can change the surface chemistry significantly and result in considerable surface deterioration, hydrophobicity loss, and enhancement of PD activity. In this work, the effect of micro and nano-fillers addition on surface degradation of SR under AC corona discharge is examined by analyzing the PD characteristics, hydrophobicity and surface morphology. Nano precipitated silica and ground silica with particle size of ∼20 nm and ∼5 µm are adopted and incorporated in RTV silicone rubber by two different mixing techniques. Mechanical stirring followed by ultrasonic water bath are applied to achieve uniform dispersion of fillers in RTV SR matrix. The four different types of the composite, i.e. pristine SR, 30-wt% micro-silica/SR, 27.5-wt% micro with 2.5-wt% nano-silica/SR and 5-wt% nanosilica/SR composites are tested under AC corona discharge. It is found that, at the end of ageing, the nano-silica composite showed the best suppression against PD activity and higher resistance against surface damage as compared to other test samples. It is also found that resistance to hydrophobicity loss is offered by composites during the initial 48 h of corona treatment but it is completely lost at the end of 96 h of ageing.

Improvement of mechanical performance of solution styrene butadiene rubber by controlling the concentration and the size of in situ derived sol–gel silica particles

Abstract: Incorporation of precipitated silica rubber compounds is now a standard technology in energy efficient green tire manufacturing process. In the present work silica nanoparticles were generated by an in situ sol–gel technique in solution styrene butadiene rubber (SSBR) using tetraethylorthosilicate (TEOS) as silica precursor. A full control over the amount of silica and size of the silica particles is realized while maintaining a good distribution and dispersion level of the nanosilica particles. In the present case the amount of synthesized silica were varied from 10–50 phr (parts per hundred) and the particles size was found to remain in the range of 200–300 nm. The in situ silica based rubber composites offer better processing characteristics as compared with standard commercial precipitated silica at the same loading level. The reinforcing character of in situ silica was further enhanced by the use of a silane coupling agent, i.e. bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT). Various instrumental techniques, such as tensile test, dynamic mechanical analysis and strain sweep analysis, abrasion test, rebound test and Mooney viscometry reveal superior mechanical performance and good processability of the in situ silica composites. Scanning and transmission electron microscopy studies indicate that the particle size distribution remains in the same range irrespective of the concentration of the silica particles.

Thermal Stability and Flammability of Styrene-Butadiene Rubber-Based (SBR) Ceramifiable Composites

Abstract: Ceramifiable styrene-butadiene (SBR)-based composites containing low-softening-point-temperature glassy frit promoting ceramification, precipitated silica, one of four thermally stable refractory fillers (halloysite, calcined kaolin, mica or wollastonite) and a sulfur-based curing system were prepared. Kinetics of vulcanization and basic mechanical properties were analyzed and added as Supplementary Materials. Combustibility of the composites was measured by means of cone calorimetry. Their thermal properties were analyzed by means of thermogravimetry and specific heat capacity determination. Activation energy of thermal decomposition was calculated using the Flynn-Wall-Ozawa method. Finally, compression strength of the composites after ceramification was measured and their micromorphology was studied by scanning electron microscopy. The addition of a ceramification-facilitating system resulted in the lowering of combustibility and significant improvement of the thermal stability of the composites. Moreover, the compression strength of the mineral structure formed after ceramification is considerably high. The most promising refractory fillers for SBR-based ceramifiable composites are mica and halloysite.

High performance fluorine rubber protective sleeve cable

Abstract: The invention discloses a high performance fluorine rubber protective sleeve cable, which comprises fluorine rubbers, methyl vinyl silicone rubbers, epoxy resins, lated-terminated liquid nitrile rubbers, polyether urethanes, acidulation starches, precipitation method precipitated silica, modified nanometer-silicon dioxide, attapulgite, expanded vermiculite, expansible graphite, zinc oxide, tearic acids, anti-aging agents, orinated paraffins, epoxidized soybean oil, adipate [2 - (2 - butoxy ethoxy) ethyl esters, triphenyl phosphate, glycerol adipic acid ester ethers, sulphur, phenyl isothiocyanate, accelerants, Nu-ammonia propyl triethoxy silane, 2,2,3,3,4,4,4- seven fluorine butyl acrylate. The high performance fluorine rubber protective sleeve cable is excellent in oil resistance and high-low temperature resistance, perfect in ageing-resistant performance and high in strength.

Comparison of adsorbent materials for herbicide diuron removal from water.

Abstract: Diuron herbicide is a persistent and frequently detected compound in surface and groundwater. In this work, a comparative study of the performance of four types of adsorbent (two precipitated silica, zeolite Y and carbon molecular sieves (CMS)) for removing diuron from water was carried out. Precipitated silica samples were obtained by controlled precipitation of SiO2 with sulphuric acid from water glass; zeolite Y was synthesized by a microwave-assisted hydrothermal method; CMS were synthesized by the method of controlled pyrolysis of wheat straw and chemical vapour deposition of organic matter. It was found that adsorption isotherms for precipitated silica and zeolite type Y are of linear shape, whereas the one for CMS exhibits at low concentrations a concave shape followed by an inflection point which suggests cooperative adsorption and the formation of adsorbate multilayers. CMS adsorbent showed the highest adsorption capacity and this was likely due to its high hydrophobicity. Temperature has...

Preparation and Characterization of Silica Material from Rice Husk Ash âÂÂAn Economically Viable Method

Abstract: Rice husk is a form of agricultural biomass that provides an abundant silicon source. Rice husks are widely burnt in agricultural fields in India because it is difficult to find other uses for them. Farmer’s burn rice hulls usually under incomplete combustion conditions to avoid accidental fires. The objective of this study was to develop a new method of amorphous silica was prepared from rice husk ash by sol-gel method. Initially received from Rice husk ash was calcined at 400°C, 500°C, 600°C and 700°C for 5 hrs to remove the volatiles in the sample and determine the amorphous structure of SiO2. Next, the thermally treated RHA was mixed with alkali solution to produce sodium silicate solution and precipitated silica was produced by the neutralization of sodium silicate solution. Rice Husks soaked in nitric acid produced the maximum amount of the sodium silicate solution and precipitated silica. Sodium oxide (Na2O) content and silica (SiO2) content in the sodium silicate solution were also determined. Extracted precipitated silica particles were characterized by Fourier transform infrared (FTIR), X-Ray diffraction and Optical microscopy techniques. The chemical composition of silica was confirmed by FTIR and SEM with EDX. Highly pure amorphous silica was derived from rice husk ash was confirmed by XRD pattern. The morphology of the obtained materials was analyzed by SEM. At optimized conditions, nano sized highly pure silica was produced with a high reactivity and 99.9% amorphous in form. This economic technology as applied to waste material also provides many benefits to the local agro industry. Thus this paper may be providing a low cost and simple method to prepare functional materials.

Precipitated Silica Derived from Palm Oil Mill Fly Ash: Kinetics and Characterization

Abstract: The silica extraction from palm oil mill fly ash (POMFA) using sodium hydroxide as one of viable processes for obtaining silica from agricultural waste was investigated. The effects of extraction time and temperature were closely examined to study the kinetics of the process. The fixed variables used in the present work were mass of POMFA 468.2 gram; the POMFA mass to NaOH volume ratio 0.2341 g/cm3; the concentration of NaOH 1.4 N and the stirring speed of 1065 RPM. The levels of temperature employed were 348 K, 358 K, 368 K and 378 K for different time durations up to 60 min. The mechanical fragmentation process was applied to obtain precipitated silica from the extracted silica. The precipitation conditions were: stirring speed of 1160 RPM, pH of 8.75, temperature of 303 K and precipitation time of 100 min. The shrinking core model (SCM) with intra-particle diffusion controlled mechanism and the Jander equation can satisfactorily represent the extraction process. The activation energy for silica extraction was 58.20 kJ/mol for the SCM with intra-particle diffusion and 62.22 kJ/mol for the Jander equation respectively. The precipitated silica agglomerate obtained at the time of 100 min has the median-weighed volume particle size distribution of 114.07 μm. The chemical composition and physical characteristic of precipitated silica which were analyzed with LPSA, XRF, XRD, FTIR and SEM are similar to the precipitated silica from the references.

Preparation method of precipitated silica thickening agent for toothpaste

Abstract: The invention relates to a preparation method of a precipitated silica thickening agent for toothpaste. The raw materials include sodium silicate, dilute sulfuric acid and tap water, the synthesis process has no need of adding any structural control agent and electrolyte, and employs saturated steam for direct heating to lower the production cost. The synthesis process adopts three-section dilute sulfuric acid adding reaction, and ensures the particle uniformity and dispersion. The method is simple and easy to operate, and can guarantee the stability of product quality. The precipitated silica obtained by the method has the characteristics of large specific surface area and excellent thickening effect, and is suitable for use as a toothpaste thickening agent. The precipitated silica thickening agent for toothpaste provided by the invention has the characteristics of: a pH value of 5.5-7.5, a DBP oil absorption value of 250-300ml/100g, a water absorption amount of 56-60ml/20g, a BET specific surface area of 240-280m /g, and an average particle size of 10-13 micrometers.

A study of the influence of a new promoter on the adhesion of rubber to a metal cord

Abstract: A promoter of adhesion of a rubber to a metal cord based on precipitated silica modified by cobalt was developed. The analysis of its qualitative and quantitative composition was carried out. The effect of the obtained compounds on the technological and physico-mechanical properties of filled elastomeric compositions based on synthetic polyisoprene rubber and on the properties of metal cord–rubber systems was studied. It was shown that application of modified precipitated silica allows both making elastomeric compositions cheaper and improving their adhesive properties.

Sand mould casting release agent prepared through precipitated silica

Abstract: The invention discloses a sand mould casting release agent prepared through precipitated silica, and relates to the technical field of precipitated silica. The sand mould casting release agent is prepared from 15-20 parts of precipitated silica, 15-20 parts of cycloaliphatic epoxide resin, 15-20 parts of melamine resin, 8-12 parts of cinerite, 5-9 parts of petroleum coke, 4-7 parts of nitrocotton, 4-7 parts of hydrogenated castor oil, 3-6 parts of asbestos wool, 3-6 parts of sulphate aluminium cement, 2-4 parts of polyacrylamide, 2-4 parts of superfine glass dust, 2-4 parts of vulcanized lard oil, 1-2 parts of nanometer titanium dioxide, 1-2 parts of nanometer rubber powder, 1-2 parts of nano-graphite powder, 0.5-1 part of aluminum powder, 0.5-1 part of rice chaff ash, 20-25 parts of n-butyl acetate and 20-25 parts of n-butyl alcohol. The release agent is directly sprayed to a sand mould, a layer of isolating membrane can be formed on the surface of the sand mould, and therefore the release effect is achieved; and in addition, the isolating membrane is high in adherence and good in high-temperature resistance and abrasive resistance, and melting and gasification can be avoided in the casting process of castings.

The properties of ethylene–propylene elastomers obtained with the use of a new cross-linking substance

Abstract: In this work, the effect of a new filler on cross-linking of ethylene–propylene rubber (EPM) was investigated. A filler with a core–shell structure ZnO/SiO2 (precipitated silica modified with zinc oxide) was introduced into rubber compounds. It was proved using of those substance to cross-link EPM caused the formation of labile ionic clusters in elastomer network. These non-covalent cross-links were generated due to interactions occurring between metal ions and functional groups of rubber (namely carboxyl groups) introduced via rubber functionalization with maleic and itaconic acids derivatives. The optimal curing time of rubber compounds was investigated. The cross-link density of the vulcanizates obtained was studied by equilibrium swelling in solvents (e.g., toluene). Additionally, the results confirmed that vulcanizates received using modified silica contained specific cross-links disintegrating under ammonia vapors. Physical relaxation at ambient temperature confirmed the influence of non-covalent cross-links on stress dissipation in the vulcanizate. The static and dynamic mechanical properties of vulcanizates obtained were also determined.

Mesoporous silica reinforced polybutadiene rubber hybrid composite

Abstract: Polybutadiene rubber (BR) hybrid composites reinforced with mesoporous silica (MPS)/nanoclays, silica and MPS/carbon black were prepared. The primary focus of this research was to incorporate the mesoporous silicate (MPS), e.g., mobil composition of matter (MCM-41) as reinforcing filler in the BR matrix. The textural properties of the mesoporous materials were characterized by powder X-ray diffraction (XRD), transmission electron microscopy and N2 isothermal adsorption measurements. The quantity of MCM-41 in the BR matrix was first optimized and the similar optimized quantity of different MPS was compared in terms of tensile strength. The composites were characterized by XRD and scanning electron microscopy. The composite containing 10 phr-loaded MCM-41 showed 250 % improvement in tensile strength compared to the matrix devoid of nanomaterial. The effects of co-incorporation of two different kinds of nanomaterials having different nanostructures, e.g., layered montmorillonite and particulate MCM-41 were also studied. MCM-41 enhanced the mechanical strength of BR almost double the value compared to precipitated silica at the same filler loading. The morphological features of the composites were well corroborated with the mechanical properties.

Low-temperature-resistant and aging-resistant chloroprene rubber composite material

Abstract: The invention discloses a low temperature-resistant and aging-resistant chloroprene rubber composite material. The low temperature-resistant and aging-resistant chloroprene rubber composite material is prepared from the following raw materials: chloroprene rubber, natural rubber, butadiene rubber, styrene-isoprene segmented copolymer rubber, polybutylene terephthalate, maleic acid grafted modified natural rubber, nano zinc oxide, nano magnesium oxide, stearic acid, 2,5-dimethyl-2,5-di-tertiary-butyl peroxide hexane, trithiocyanuric acid, triallyl trimellitate, nano silica, precipitated silica, purple carbon black, nano microcrystalline cellulose, silane coupling agent KH-550 modified montmorillonoid, an anti-aging agent, an accelerant NA-22, an accelerant TE, an accelerant ZIP, vinyl tri(beta-methoxyl ethyoxyl) silane, dioctyl azelate, dioctyl sebacate and a titanate coupling agent NDZ-201. The low temperature-resistant and aging-resistant chloroprene rubber composite material disclosed by the invention has the advantages of high strength, good low temperature resistance and excellent aging resistance.

Oil-proof and anti-aging control cable

Abstract: The invention discloses an oil-proof and anti-aging control cable. The control cable comprises a wire, an insulating layer and a sheath, wherein the sheath is prepared from ethylene-propylene-diene monomer rubber composite; the ethylene-propylene-diene monomer rubber composite comprises raw materials as follows: ethylene-propylene-diene monomer rubber, nitrile rubber, polypropylene, chlorinated polyethylene, stearic acid, zinc oxide, superfine fully-vulcanized powder nitrile rubber, sulfur, nano silicon nitride, zinc methacrylate, silica fume, superfine silicon dioxide, precipitated silica, nano boron nitride, 3-mercaptopropylmethyldimethoxysilane, lanthanum glutamate dithiocarbamate, 2,2,3,3,4,4,4-heptafluorine butyl acrylate, polytetrafluoroethylene, perfluoromethyl vinyl ether, petroleum wax, naphthenic oil, an anti-ageing agent and an accelerator. The oil-proof and anti-aging control cable has excellent oil resistance, good ageing resistance, high mechanical strength and long service life.

Tire with rubber component containing reinforcement comprised of precipitated silica and functionalized graphene

Abstract: This invention relates to a tire having a rubber component, such as a tread. with filler reinforcement containing surface modified graphene and precipitated silica which may be or may include pre-hydrophobated precipitated silica.