Effect Of Silica Particles Research Articles

Influence of silica particles on mucociliary structure and MUC5B expression in airways of C57BL/6 mice

Purpose: Impaired mucociliary clearance is an initial characteristic of recurrent cough, respiratory infection and chronic respiratory diseases. It has been demonstrated that prolonged inhalation of respirable silica particles results in a variety of pulmonary diseases, but whether the mucociliary system is involved in this process is unclear. This study aims to evaluate the effects of silica particles on mucociliary structure and MUC5B production in respiratory tract.Materials and Methods: C57BL/6 mice were administered with 2.5 mg silica particles through a single intratracheal instillation. The changes of mucociliary structure and MUC5B expression in trachea was evaluated by HE and AB-PAS staining, transmission electron microscopy and immunohistochemistry on days 1, 7, 28 and 84 post-exposure.Results: The mucociliary structure of airway epithelium was obviously impaired by silica particles, showing disordered, shortened or partially lost cilia on the surface, increased mucus in mucous layer and submucosal glands from day 7 to day 84. A variety of ultrastructural abnormalities were discovered in silica-exposed airway cilia, including absence of central pair microtubules, disorganized microtubules and clusters of axoneme on day 1 and 7. The numbers of ciliary axonemes and basal bodies in ciliated epithelial cells were significantly decreased, whereas the proportion of abnormal axonemes was gradually increased with exposure to silica particles (P < 0.05). In addition, silica particles significantly decreased MUC5B expression on the surface of airway epithelium on day 28 and 84, but obviously increased its production in submucosal glands from day 1 to day 84 (P < 0.01).Conclusions: Silica particles could lead to ultrastructural defects in airway cilia, mucus hypersecretion and altered MUC5B expression in trachea, indicating that impaired mucociliary structure and altered MUC5B production might participate in the development of silica-related respiratory diseases.

Role of silica nanoparticles on network formation and properties in thermoset polycarbonate based nanocomposites

Nanocomposites based on thermoset polycarbonate and fumed silica nanoparticles were prepared by radical in situ polymerization. To avoid nanoparticle agglomeration, silica nanoparticles modified with a vinyl end capped silane agent were also used. The effect of silica particles and silica surface modification on the extent of polymerization and network density was evaluated. Silica nanoparticles reduced the amount of soluble oligomeric species forming during the diallyl carbonate polymerization and this was particularly pronounced in the case of modified silica. Nevertheless, the participation of surface modifier reactive groups to polymerization also caused a lower polycarbonate network density. SEM analysis showed that the proposed interfacial strategy was effective to control nanoparticle dispersion; no agglomeration phenomena were observed using modified silica. Nanocomposites preserved the polycarbonate stiffness while a toughness increase was recorded with the addition of neat silica. Particularly interesting was the effect of nanoparticles on the improvement of the abrasion resistance of the polycarbonate thus overcoming one of the drawback of this material.

Effect of silica particles on vortex dynamics in a micro-contraction channel flow of poly(ethylene oxide) solutions

The effect of silica particles in poly(ethylene oxide) (PEO) solutions on both the rheological properties and vortex dynamics under a micro-contraction channel flow was investigated. Although most materials used in industry are not only polymeric solutions or melts but also the suspensions consisting of particles as well as polymers, studies on the interaction between particle-polymer and their vortex behaviors under contraction flow are rare. The effect of silica particles was demonstrated in comparisons between PEO solutions and silica/PEO suspensions. The addition of 1.0wt% of silica particles decreased the vortex size and delayed the formation of a lip vortex and a subsequent corner vortex. As the silica concentration increased, the vortex size increased and the flow rate at which the lip vortex and corner vortex formed decreased. The vortex behavior inside the micro-contraction channel was related more to the storage modulus than to the viscosity. The storage modulus also decreased initially and then increased with the silica concentration, similar to the vortex size. The decreases in the vortex size and the storage modulus were due to the adsorption of polymers onto the silica particles. The storage modulus increased with an increase in the silica concentration when the amount of free polymer was kept nearly constant. The same tendency was observed when the suspension was supplied with additional polymers corresponding to the amount of adsorbed polymer.

Structure and morphology of silica-reinforced polypropylene composites modified with m-EPR copolymers

The effects of different silica (SiO2) types and different contents of two metallocene propylene-based m-EPR elastomers (differing in molecular weight and viscosity) on interfacial properties, structure and morphology of isotactic polypropylene/SiO2/m-EPR composites were investigated. Four silica fillers differing in size (nano- vs. micro-) and surface properties (hydrophilic vs. hydrophobic i.e. polar vs. non-polar) were chosen and added in 4 vol% to isotactic polypropylene. The m-EPR elastomers were added to iPP/SiO2 96/4 composites as possible impact modifier and compatibilizer at the same time in 5, 10, 15, and 20 vol% per 100 vol% of composites (phr). The investigation confirmed the overall prevailing of separated morphology of ternary iPP/SiO2/m-EPR composites, i.e. selectivity of dispersed m-EPR and silica particles toward iPP matrix as was predicted on the basis of adhesion properties. The increase of crystallinity degree and spherulite size with addition of m-EPR elastomers indicated significant solidification effect of added elastomers in addition to opposite nucleation effect of silica particles owing to surface character of filler. The effects of different silica fillers and different contents of two m-EPR elastomers were discussed within the context of morphology/structure-adhesion property relationships of the iPP/SiO2/m-EPR composites.

Influence of Nanosize Silica Particles on the Rheological Behaviour of Lyotropic Cubic Phase of Glucopone (APG) Surfactant

The effect of nanosize silica particle on the stability, structures and rheological behaviours of cubic liquid crystalline phases of Glucopone/water/heptane system were investigated. Small-angle X-ray scattering (SAXS) and polarizing microscope were used for phase identification and structure characterization. SAXS scattering profile was characteristic to cubic phase before and after the addition of silica particles. The cubic samples showed several diffraction peaks and can be assigned to the Ia3d space group. The area per surfactant molecule was found to increase as the silica concentrations was increased. Moreover, the rheological study on the cubic phase with different silica concentration was performed. The frequency-dependent storage and loss modulus were found to be characteristic of the cubic phase in the linear viscoelastic region. The cubic samples behave as solid-like material with storage modulus G’~ 0.7106 Pa typical of cubic lyotropic materials. The elasticity of cubic samples was found to increase with silica concentration. The increase in the elasticity was ascribed to the network and the formation of smaller structure as indicated by SAXS measurements. As temperature was further increased a decreased in the elasticity was observed confirming the structural change as indicated by the change in slopes of G’ and G”. The cubic samples exhibited shear thinning behaviours, with the dynamic viscosity being affected by the silica particles concentrations and the effect of silica particles on the rheological behaviours was quite noticeable as the concentration increased. The results showed strong correlation between rheology and microstructural changes in the dispersion of nanoparticle silica in the cubic phase system.

The influence of mesoporous silica in low Tg cyclic olefin copolymer nanocomposite films: Mechanical and moisture barrier studies

In this study, mesoporous silica-cyclic olefin copolymer nanocomposite films were fabricated by solution casting. With an increase in silica loading, the stiffness of the matrix increased. The nanocomposite film shows increased strain to failure with moisture after aging by matrix plasticization. The storage modulus and loss factor for samples with silica content show better results compared with pristine polymer, as indicated by dynamic mechanical analysis. The interaction between filler-polymer chain exhibit hydrophobicity compared to the neat polymer. Water absorption studies at room temperature and near the T-g of the polymer (similar to 64 degrees C) were carried out. The nanocomposites up to 4 wt% filler reduces the water diffusion by forming hydrogen and chemical bonding. The result by calcium degradation test method for moisture permeability and Schottky structured organic device encapsulation under weathering condition confirms the effective reinforcement effect of silica particles in the matrix. (C) 2014 Elsevier Ltd. All rights reserved.

Silica Nanoparticle Doped Organic Ionic Plastic Crystal Electrolytes for Highly Efficient Solid-State Dye-Sensitized Solar Cells

Organic ionic plastic crystal, 1-propyl-1-methylpyrrolidinium iodide (P₁₃I), which possesses a broad plastic phase from -36 to 135 °C, was doped with silica nanoparticles (SiO₂ NPs) and 1-ethyl-3-methylimidazolium iodide (EMII), for the preparation of SiO₂/EMII/P₁₃I solid-state electrolytes for dye-sensitized solar cells (DSSCs). The thermal properties of all the electrolytes, including solid-solid phase transitions and melting temperatures, were investigated by differential scanning calorimetry (DSC). The effect of silica particles on the ionic conductivity, diffusion of I⁻/I₃⁻ redox couple in electrolytes, and photovoltaic performance for solid-state DSSCs were investigated. The fabricated solid-state DSSCs yielded a high power conversion efficiency of 5.25% under simulated air mass 1.5 solar spectrum illuminations at 50 mW cm⁻². Furthermore, the DSSCs based on SiO₂/EMII/P₁₃I solid-state electrolytes show good stability after an accelerating aging test, demonstrating potential practical applications.

Effect of Silica Particles on Stability of Highly Concentrated Water-in-Oil Emulsions with Non-Ionic Surfactant

Effect of Silica Particles on Stability of Highly Concentrated Water-in-Oil Emulsions with Non-Ionic Surfactant

Effect of silica particles on stability of highly concentrated water-in-oil emulsions with non-ionic surfactant

Water-in-oil, high internal phase emulsion made of super-cooled aqueous solution containing a mixture of inorganic salts and stabilized with non-ionic surfactant (sorbitan monooleate) alone was investigated. It was not possible to produce a highly concentrated emulsion (with aqueous phase fraction = 94 wt %), stabilized with surface-treated silica, solely: we were able to form an emulsion with a maximal aqueous phase mass fraction of 85 wt % (emulsion inverts/breaks above this concentration). The inversion point is dependent on the silica particle concentration, presence of salt in the aqueous phase, and does not depend on the pH of the dispersed phase. All emulsions stabilized by the nanoparticles solely were unstable to shear. So, the rheological properties and stability of the emulsions containing super-cooled dispersed phase, with regards to crystallization, were determined for an emulsion stabilized by non-ionic surfactant only. The results were compared to the properties obtained for emulsions stabilized by surface treated (relatively hydrophobic) silica nanoparticles as a co-surfactant to sorbitan monooleate. The influence of the particle concentration, type of silica surface treatment, particle/surfactant ratio on emulsification and emulsion rheological properties was studied. The presence of the particles as a co-stabilizer increases the stability of all emulsions. Also, it was found that the particle/surfactant ratio is important since the most stable emulsions are those where particles dominate over the surfactant, when the surfactant’s role is to create bridging flocculation of the particles. The combination of the two types of hydrophobic silica particles as co-surfactants is: one that resides at the water/oil interface and provides a steric boundary and another that remains in the oil phase creating a 3D-network throughout the oil phase, which is even more beneficiary in terms of the emulsion stability.

Crystallization behavior of polybutadiene containing silica particles

AbstractThe effect of silica particles (silica), which are petroleum‐free products, on the isothermal and nonisothermal crystallizations of cis‐1,4‐poly(butadiene) rubber (BR) is investigated. DSC measurements reveal that silica accelerates the crystallization of BR. As a result, BR‐containing silica shows crystallization even after crosslinking reaction. Because of the enhanced crystallization, the tensile modulus is much higher than that without silica in the range between the glass transition temperature and the melting point. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

PES/SiO2 nanocomposite by in situ polymerization: Synthesis, structure, properties, and new applications

SiO_2 nanoparticles of a quantum size (15 nm or less) were prepared via sol–gel method using tetraethylorthosilicate as a precursor. SiO_2 nanoparticles were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) analyses. Polyethersulfone/silica (PES/SiO_2) crystal structure nanocomposite was prepared by in situ polymerization using silica nanoparticles as reinforcement filler. The polymerization reaction was done at 160°C in paraffin bath in the presence of diphenolic monomers. XRD and FESEM analyses were used to study the morphology of the synthesized nanocomposite. The purity and thermal property of the PES/SiO_2 nanocomposite were studied by energy dispersion of X-ray analysis and differential scanning calorimetry, respectively. The effect of silica particles on the hydrophilicity of PES/SiO_2 nanocomposite was also investigated. It was showed that the PES/SiO_2 nanocomposite had a higher swelling degree when compared with the pure PES. The synthesized PES/SiO_2 powder was used to remove Cu(II) ions from its aqueous solution. The effect of experimental conditions such as pH, shaking time, and sorbent mass on adsorption capacity of PES/SiO_2 nanocomposite were investigated. It was found that incorporation of a low amount of silica (2 wt%) into the polymer matrix caused the increase of the Cu(II) ions adsorption capacity of PES. POLYM. COMPOS., 2012.

Effect of silica particles on the stability of methane hydrates

A systematic study of methane hydrate formation and dissociation was carried out in the suspensions of silica (diameter 50, 150 and 200μm) and natural bentonite-clay (collected from ∼40mbsf) from Krishna–Godavari (KG) basin. All the experiments were carried out in a stirred reactor using 10wt% of silica and natural sediment samples. Presence of silica or bentonite-clay did not show any noticeable shift in methane hydrate dissociation corroborating the literature, however, nucleation and growth of hydrates were quicker in the presence of silica or bentonite system compared to pure hydrate system. The silica grains have also shown considerable effect on release of methane during the dissociation.

Preparation and Characterization of Poly(Acrylamide)/Silica Nanocomposite Gels

A series of PAM/silica nanocomposite (NC) gels using silica sol as the inorganic component were prepared by in situ free-radical polymerization. The addition of silica sol was first used to bring silica nanoparticles to form organic (polymer)/inorganic system. Results from the swelling experiment indicated that the effect of silica particle was nevertheless rather complex as polymer/particle binding. Additionally, it revealed that the swelling ratio of the NC gels with a certain silica content increased with the increasing pH value. Moreover, it exhibited absorption of the polymer onto silica because the chemical cross-linked PAM has changed to the organic/inorganic system. The spectroscopic results showed that the silica nanoparticles formed by silica sol promoted high degree of attachment to the polymer chain. The AFM micrographs displayed that silica particles were of nano degree and in the monodisperse. Both evidences proved that the organic/inorganic system was effectively formed through the addition of silica sol.

Effects of silica particles on the electrical percolation threshold and thermomechanical properties of epoxy/silver nanocomposites

We experimentally and theoretically demonstrated that the addition of silica particles could improve both the electrical conductivity and the thermomechanical properties of epoxy/silver nanocomposites. As silica particles were added, the electrical percolation threshold concentration of silver nanoparticles decreased and the electrical resistivity of the composite decreased by about 8 orders of magnitude. The coefficient of thermal expansion also decreased with increasing volume fraction of silica particles. Molecular simulations showed that the additional silica particles made the effective intermolecular interactions between silver nanoparticles attractive, thereby enhancing the formation of an electrical percolation network.

Influence of addition of silica particles on reaction-induced phase separation and properties of epoxy/PEI blends

Polyether imides (PEI)/silica nanocomposites, prepared by sol–gel process, were used to modify the epoxy resin (ER), and the effect of silica particles on reaction-induced phase separation and mechanical properties of these systems were investigated. SEM images of the fracture surface of ER/PEI/silica composites showed an interesting morphology transformation with the increase of silica particle content. SEM–EDX results indicated that silica particles once formed in the PEI gradually migrated and concentrated in epoxy-rich region during the phase separation because of the better affinity between silica particles and epoxy resin. FTIR measurement and rheological test confirmed that the silica particles make the polymerization reaction of epoxy faster and the dynamic DSC results demonstrated that the activation energy of these systems decreased with the increase of the silica particles. Mechanical measurements approved that the introducing of PEI/silica nanocomposites into the epoxy could lead to great improvement of the impact strength and storage module.

エポキシ樹脂複合材料の力学的特性に及ぼすシリカ粒子充填の効果

エポキシ樹脂複合材料の力学的特性に及ぼすシリカ粒子充填の効果

Intumescent mineral fire retardant systems in ethylene–vinyl acetate copolymer: Effect of silica particles on char cohesion

Silica particles of different physical properties (particle size, morphology and specific surface area) were introduced into an ethylene–vinyl acetate copolymer filled with an intumescent mineral fire retardant system containing magnesium hydroxide and organo-modified montmorillonites. The effect of silica particles on the cohesion and strength of the foamed combustion residue was studied by micro-indentation, concurrently with the characterization of material's fire behavior. Silica particles seem to act as defects that generate cracks, decreasing the strength of the residue. This generation of cracks is connected to a lower cohesion of the residue, especially for silica particles of high specific surface area. In parallel, the presence of silica of high specific surface area, despite tending to decrease Time To Ignition, also improves self-extinguishing ability, thanks to a better thermal stability at higher temperatures, and reduces the maximum Heat Release Rate in cone calorimeter tests.

氷・シリカ粒子混合物の変形実験：流動則に対するシリカ粒子の効果と氷天体テクトニクスへの応用

氷・シリカ粒子混合物の変形実験：流動則に対するシリカ粒子の効果と氷天体テクトニクスへの応用