Sol Content Research Articles

Facile fabrication and modification of polyacrylate/silica nanocomposite latexes prepared by silica sol and silane coupling agent

Polyacrylate/silica nanocomposite latexes were prepared by silica sol and facilely modified with a silane coupling agent γ-methacryloxypropyltrimethoxysilane (KH-570) aimed at reinforcing the interaction between silica nanoparticles and latex particles in a convenient way. The effects of silica sol and KH-570 amounts on the performance of latexes and films are discussed. Particle size and morphology tests demonstrated that the silica nanoparticles could form hydrogen bond interactions between latex particles, and thus influence the rheological properties of latexes. Tensile measurements and SEM photographs showed the reinforcing and toughening roles of silica nanoparticles. SEM images also indicated that the addition of silica sol increased the roughness of films, which resulted in the increase of hydrophilic silanol groups on the film surface and the decrease of water resistance of latex films. The latex films retained good adhesion force, flexibility, and impact resistance even when the silica sol content was as much as 25%. TGA data revealed that the incorporation of silica sol enhanced the thermal stability of the films. After introducing KH-570, the particle size increased with the increase of the amount of KH-570. Moreover, the addition of KH-570 improved the water resistance and maintained other properties of the latex films appropriately.

Spontaneous Formation of Vertically Aligned Lamellae in Thin Films of Block Copolymer–Silica Hybrid Material

Abstract Vertical alignment of mesoscaled and phase-separated structures in organic–inorganic hybrid materials has significant potential for various applications. However, particular procedures and treatments are required to generate such pattern geometries. We demonstrate herein a simple and spontaneous process for vertical alignment of mesoscopic phase-separated structures in a hybrid material consisting of an amphiphilic block copolymer that possesses a thermotropic liquid crystal framework and silicate sol. By combining the thermotropic and lyotropic liquid crystal properties, the sol–gel condensation in this system spontaneously leads to the vertical alignment of mesoscopic lamellae. Most likely, the vertical molecular orientation formed in the thermotropic smectic liquid crystal domains promotes the vertical alignment of the mesoscaled lyotropic liquid crystalline structure of the hybrid film. The organic block components in the film could be selectively etched by ultraviolet light/ozone treatment and, consequently, provide a topologically undulated silica film that retains the vertical lamella structure of the precursor hybrid film. This approach via the hybridization with a metal oxide sol solution is advantageous in tuning the lateral pitch of the structure simply by adjusting the volume fraction of precursor sol content.

SOL-ENHANCED Au–Ni–TiO2 ELECTROPLATED COATINGS

A sol-enhanced gold ( Au ) — nickel ( Ni ) — titanium dioxide ( TiO 2) composite coating technique has been developed at the University of Auckland. The aim of the present study is to achieve quality control and thickness homogeneity of the coatings in order to scale up this process to the workshop level. Multi-coating samples were prepared in the same electroplating unit with same processing parameters. The thickness variation and influence of titanium dioxide ( TiO 2) sol content on the thickness have been studied. The consumption of Au and Ti ions in the electrolytes during the electroplating process was measured by inductively coupled plasma-mass spectrometry (ICP–MS) method. The cross-section microstructures of coatings were studied by field emission scanning electron microscope (FESEM) with an energy dispersive spectroscopy (EDS) system. An optimized processing method has been put forward for the industry process to produce coatings with uniform thickness and good quality.

Self-Structuring in Amphiphilic Networks Prepared by Single Conventional Radical Copolymerization of n-Butyl Methacrylate and Vinylpyrrolidone

Amphiphilic networks segregated in hydrophilic and hydrophobic domains are very attractive materials because they show unique properties related to the combination of both components. In this work, these types of networks have been obtained in a very simple way by a single standard bulk radical photocopolymerization of vinylpyrrolidone, and n-butyl methacrylate, in the presence of 1 mol % of cross-linkers with different methacrylate or VP-like functionalities. The cross-linker functionalities have been shown to have a strong influence on the sol content and on the different properties of the materials, such as segregation or the variation of the storage modulus with temperature and hydration. The compositional data of the polymeric chains of this sol content are in good agreement with the theoretical prediction of the polymerization carried out assuming that the reaction may be described compositionally by the terminal model. The most efficient cross-linking was obtained using an asymmetric cross-linker bearing simultaneously methacrylate and VP-like groups.

Porous-layer capillary gas chromatography columns with a hybrid structured sorbent based on alkyltriethoxysilane

Porous-layer capillary columns with a hybrid organic-inorganic sorbent based on structured silica are described. Properties of the prepared columns are discussed. Examples of separating C1–C4 hydrocarbons and a mixture of solvents on the obtained columns are presented. It is shown that changes in the organic component content of the original sol make it possible to control the selectivity of porous-layer columns.

Oil Column Method for Magnetic Microspheres with Core-Shell Structure

Spherical alumina catalysts have been widely used in fluidized bed and slurry-bed or catalyst carrier due to their excellent pore structure, large surface area, good physical strength and resistance to acids and stability. Magnetic microspheres of γ-Fe2O3 @ Al2O3 with core-shell structure were obtained by γ-Fe2O3 magnetic core coating with aluminum sol. After aging, drying and calcinations process, microspheres with certain hardness and magnetic properties can be obtained. During the preparation of core-shell structure microspheres, effect of both the content of aluminum sol, hexamethylenetetramine(HMT), magnetic core γ-Fe2O3 and process parameters of shaping time, aging temperature, calcination temperature on the properties of the spherical carrier was investigated. The optimum properties of microsphere carrier for hardness of 36.32 N/mm, specific surface area of 89.016 m2/g, pore volume of 0.874 cm3/g and average pore diameter 18.51 nm were synthesized, respectively.

KF/Al<sub>2</sub>O<sub>3</sub>/Ceramic Membrane Catalyst for Biodiesel Production

In this work, γ-Al2O3coated ceramic membrane (CM) was prepared by dip-coating technique and used as a catalyst support for biodiesel production. The effects of the properties of the slurry were investigated on the γ-Al2O3coating. KF/Al2O3/CM was prepared by γ-Al2O3/CM impragnated with KF solution. The samples were studied in the transesterification of palm oil with methanol. Experimental results showed that the solid content and density of the aluminum sol had significant influences on the amount and stability of the γ-Al2O3coating. KF/γ-Al2O3/CM showed a high activity and reusability in the transesterification. This work provided a way to prepare alkaline ceramic membrane which can be used in the membrane reactor to produce biodiesel.

Synthesis and Characterization of Drug‐Loaded Poly(ε‐caprolactone)/Silica Hybrid Nanofibrous Scaffolds

We produced drug‐loaded poly(ε‐caprolactone) (PCL)/silica hybrid nanofibrous scaffolds with various silica sol contents (0 vol%, 10 vol%, 15 vol%, and 20 vol%) using electrospinning and examined their physicochemical properties, mechanical properties, drug release behavior, and in vitro biocompatibility to evaluate their potential application for guided bone regeneration (GBR). The loading efficiency of tetracycline hydrochloride (TCH) drug was remarkably enhanced by hybridizing the PCL solution with the silica sol. All produced hybrid scaffolds had a highly nanofibrous structure, in which the silica phase was homogeneously hybridized with the PCL polymer, while preserving their intrinsic characteristics. This led to considerable increases in hydrophilicity and mechanical properties (e.g., ultimate tensile strength and elastic modulus). In addition, the release rate and cumulative maximum amounts of the TCH from the hybrid scaffolds significantly increased with increasing the silica content, while all produced hybrid nanofibrous scaffolds showed good biocompatibility assessed by in vitro cell tests.

Application of Photocatalytic Nanomaterials in Prevention from <i>Sphaerothecaf uliginea In Vivo</i>

This study was conducted to investigate the efficiency of TiO2 photocatalytic nanomaterial as a novel environment-friendly disinfectant to control plant fungal diseases (Sphaerothecaf uliginea) by its photochemical sterilization ability in cucumber plants. Anatase nano-TiO2 sol, a neutral, viscous aqueous colloid of 1.4% TiO2, was synthesized by sol-gel method. Control efficiencies of nano-TiO2 sol in preventing from powdery mildew were measured by field experimental method with cucumber seedling naturally infected Sphaerothecaf uliginea. Results showed that spraying certain content of nano-TiO2 sol could form continuous and stable antibacterial films on blade surfaces which could not only significantly reduce lesion areas, disease incidences and disease indexes of powdery mildew but also make the leaves turn much greener. It was initially confirmed that nano-TiO2 sol could effectively delay and inhibit the development and pervasion of cucumber powdery mildew. These results indicate that nano-TiO2 sol can be developed as environment-friendly fungicide in preventing from plant disease developments.

RECLAIMING OF GROUND RUBBER TIRE BY SAFE MULTIFUNCTIONAL RUBBER ADDITIVES: I. TETRA BENZYL THIURAM DISULFIDE

ABSTRACT The present paper describes the mechanical reclaiming of ground rubber tire (GRT) by safe tetra benzyl thiuram disulfide (TBzTD), a multifunctional rubber additive. The versatility of the proposed agent is that it acts as a reclaiming agent during reclaiming and as a curing agent during revulcanization of the reclaimed materials. In this regard, we want to introduce a safe reclaiming agent in reclamation of GRT for improving its physical and mechanical performance. Reclaiming GRT has been carried out in an open roll mixing mill at various time intervals and different concentrations of the reclaiming agent (TBzTD) in the presence of spindle oil. The degree of reclaiming has been evaluated by the measurement of sol content, gel content, Mooney viscosity, inherent viscosity of sol rubber, and degree of cross-link of the reclaimed materials as a function of milling time. Also, the influence of gel content on cross-link density at various time intervals on the open two roll mixing mill has been determined. A unique correlation between gel fraction and cross-link density obtained at various time intervals and concentrations of reclaiming agent indicate that an optimization of the concentration of safe TBzTD and milling time has a positive influence on improving the efficiency of reclamation. The reclaiming conditions have been optimized in view of the mechanical properties of the revulcanized GRT and the aging resistance properties of the revulcanized reclaim. The influences of the concentration on the mechanical properties in the revulcanized reclaim have also been studied. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the revulcanized reclaimed rubber when reclamation is carried out by optimum concentration of safe TBzTD after maximum time of reclaiming.

Photo-Cross-Linked Poly(ethylene carbonate) Elastomers: Synthesis, in Vivo Degradation, and Determination of in Vivo Degradation Mechanism

Low-molecular-weight poly(ethylene carbonate) diols of varying molecular weight were generated through catalyzed thermal degradation of high-molecular-weight poly(ethylene carbonate). These polymers were then end functionalized with acrylate groups. The resulting α,ω-diacrylates were effectively photo-cross-linked upon exposure to long-wave UV light in the presence of a photoinitiator to yield rubbery networks of low sol content. The degree of cross-linking effectively controlled the in vivo degradation rate of the networks by adherent macrophages; higher cross-link densities yielded slower degradation rates. The cross-link density did not affect the number of adherent macrophages at the elastomer/tissue interface, indicating that cross-linking affected the susceptibility of the elastomer to degradative species released by the macrophages. The reactive species likely responsible for in vivo degradation appears to be superoxide anion, as the in vivo results were in agreement with in vitro degradation via superoxide anion, while cholesterol esterase, known to degrade similar poly(alkylene carbonate)s, had no affect on elastomer degradation.

Synthesis of hybrid hydrogel of poly(AM co DADMAC)/silica sol and removal of methyl orange from aqueous solutions

A hybrid hydrogel (poly(AM co DADMAC)/silica sol) from acrylamide (AM), diallyl dimethyl ammonium chloride (DADMAC) and silica sol was prepared by aqueous solution polymerization, using N,N′-methylenebisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. Its structure and characterization were determined by means of FTIR, SEM, TEM and TG; meanwhile, the effects of silica sol content, pH values and temperatures were studied on the adsorption of methyl orange onto (poly(AM co DADMAC)/silica sol (PAMDS). The adsorption rate data and adsorption equilibrium data were analyzed based on the pseudo-second-order model and four isotherm models respectively. Results obtained from this study indicated that the kinetic behavior accorded with the pseudo-second-order kinetic model. The isotherm behavior can be explained by the Langmuir, Freundluich and Generalized isotherm models. The activation energy was also evaluated for the removal of methyl orange onto PAMDS. This hybrid hydrogel may be used as good adsorbent for the adsorption of anionic dyes from effluents.

Synthesis, characterization and flame retardant of UV-curable hybrid coatings containing SiO2–P2O5–B2O3 via sol–gel method

A ternary sol containing silicon, phosphorus and boron modified by γ-methacryloxypropyltrimethoxysilane was synthesized by sol–gel method. The ternary sol was incorporated into the organic matrix and UV-curable organic/inorganic hybrid coating materials were obtained. Hardness, transmittance, haze, cross-cut adhesion and abrasion resistance results showed that the mechanical properties of the hybrid coatings improved effectively with no comprising on optical properties by increasing sol content. Scanning electron microscopy and Energy Dispersive X-ray spectrometer studies indicated that inorganic particles were homogenously dispersed in the organic matrix. The flame retardancy of the UV-curable coatings was investigated by thermogravimetric analysis and microscale combustion calorimeter. The results showed that the incorporation of sol into the organic network led to an improvement in the thermal stability and flame retardancy of the hybrid coating materials. It is a desirable achievement to improve simultaneously both flame retardancy and mechanical properties of the coatings.

Thermosetting allyl resins derived from soybean fatty acids

AbstractA novel class of thermosetting resins based on allylated and transesterified epoxidized soybean oil (AE‐ESBO) curable by radical mechanism was developed. The AE‐ESBO was prepared from ESBO by oxirane ring‐opening and then transesterification with allyl alcohol. A family of rubbery to glassy resins was prepared by radical copolymerization of AE‐ESBO with different concentrations of maleic anhydride (MA). Glass transition temperatures (Tg) of these resins ranged from below room temperature to about 130°C based on the amount of MA. In spite of the presence of anhydride groups, water absorption was low <2% even when maleic anhydride was 30% of total weight. Low sol content after extraction and low swelling in toluene indicated high crosslinking density. Tensile moduli of these resins were up to 1.4 GPa and tensile strengths up to 37 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Viability of human umbilical cord–derived mesenchymal stem cells in G-rich and M-rich alginates

In this study, the effect of pharmaceutical-grade alginates on the cell viability of human mesenchymal stem cells derived from umbilical cord was examined and their use in tissue engineering applications was evaluated. The effects of the ratio of the copolymer building blocks (guluronic and mannuronic acids) and their interactions with divalent calcium, the purity of alginates (proteins and polyphenol content), and gelation factors (calcium concentration and sol content) were examined. The high guluronic acid content in the alginates improved the viability of the human mesenchymal stem cells derived from umbilical cord and supported cell growth significantly. It was confirmed that the sol fraction of alginate reduced cell viability. Cells in the presence of alginate beads cross-linked with 50 and 100 mM calcium chloride showed maximum viability; the protein and polyphenol content of the alginates did not affect the viability of the human mesenchymal stem cells derived from umbilical cord, while the monomer ratio did have an obvious effect.

Anticorrosion performance of eco-friendly silane primer for coil coating applications

In this paper, corrosion resistance and adhesion of environmental friendly silane primer on coil substrate was studied. Primer was formulated by using methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane via acid hydrolysis and condensation reaction. Three different formulations (5%, 15% and 30%) were developed on the basis of sol/water ratio. Aluminium coils was dipped into primer and cured at 120°C for 20min. Fourier Transform Infrared Spectroscopy and Scanning Electron Microscope was used to analyse the structural and morphological behaviour of the coating. Corrosion resistance of the coating was evaluated by salt-spray test and potentiodynamic polarization measurement. The adhesion behaviour of the coating was investigated by cross hatch test, before and after salt-spray immersion. Results showed that 15wt% sol content showed significant improvement in the corrosion resistance, adhesion of the coating and its UV resistance. Silane primers have excellent adhesion with substrate and commercial grade polyester, polyurethane and polyvinyldiene fluoride top coats.

Formation of Sol–Gel-Derived TaOxNy Photocatalysts

Tantalum oxynitride (TaON) is a visible photocatalyst (λ < 520 nm) that has been investigated for green energy applications, specifically, the solar production of hydrogen gas. Metal oxynitrides are often generated by the ammonolysis of metal oxides at very high temperatures. We have investigated an alternative synthetic procedure to produce gram-scale quantities of photocatalytically active TaOxNy materials using room-temperature sol–gel chemistry. X-ray photoelectron spectroscopy (XPS) results confirm that nitrogen was incorporated into materials with a Ta2O5 crystal structure. Optical characterization reveals that sol–gel-synthesized TaOxNy has a 2.3 eV bandgap, in agreement with bulk TaON. Furthermore, photoluminescence experiments reveal that two distinct material systems are being created during the initial sol phase of the synthesis: one species is primarily metal oxide, while the other is a N-doped species. This observation may lead to synthetic methods that improve the doping content of sol–gel-derived materials.

Preparation of Magnetic Expanded Graphite by Sol-Gel Method and its Electromagnetic Properties

In order to transform the diamagnetism of expanded graphite (EG) to ferrimagnetism and improve its electromagnetic interferential capability, nano γ-Fe2O3/EG magnetic composite materials was prepared by sol-gel and low temperature self-combustion technique. The as prepared samples were characterized by SEM, XRD and Magnetic hysteresis cycle test. The results indicated that the composite materials had ferrimagnetism property after the embedding of γ-Fe2O3, but the average conductivity of the composites decreases gradually with the increase of γ-Fe2O3. Different mixing ratio of ferrite gel and graphite intercalation compounds produced ferric oxide with different crystal form and shape. When the content of ferrite sol was low, spherical γ-Fe2O3with the mean size of 31.69nm was formed, and spread unevenly on the surface and interformational micelles of EG. High content of ferrite sol (83wt%) produced more perfect crystal γ-Fe2O3of pentahedron shape with the mean size of 44.68nm, and a few of α-Fe2O3occurred which lead to the decline of the magnetic property of the composite materials.

Preparation of Polyacrylate/ZnO Nanocomposite

In this study, ZnO sol was prepared by sol-gel method with zinc acetate, triethanolamine and sodium hydroxide as the main material. Then obtained ZnO sol was directly blended with polyacrylate latex to prepare polyacrylate/ZnO nanocomposite. The effects of ZnO sol contents on the mechanical properties and water absorption of polyacrylate/ZnO nanocomposite were investigated in details. The results showed tensile strength of polyacrylate/ZnO nanocomposite reduced, and water absorption of it increased with the increasing of ZnO sol. Transmission electron micrograph (TEM) analysis indicated ZnO sol dispersed uniformly and the size of it was about 20nm. Scanning electronic microscope (SEM) analysis showed ZnO sol and polyacrylate have good compatibility, however, ZnO sol would condensate and form short rods structure during the film forming process.

Effects of silica sol content on the properties of poly(acrylamide)/silica composite hydrogel

Silica sol was first used as an inorganic component to form poly(acrylamide) (PAM)/silica composite hydrogels via in situ free-radical polymerization. The gelation reaction of the composite materials was monitored on a rheometer, indicating that the gelling induction time becomes longer with the increasing content of silica sol. Compression strength and elastic modulus of the composite hydrogels were significantly improved by adding silica sol compared with pure PAM hydrogels. Silica particles formed by silica sol were dispersed on the surface of PAM polymer network in nanosize, promoting high degree of attachment to the polymer chain and enhancing the interfacial interaction between these two components. TGA analysis showed that the silica stiffens the hydrogel network by creating additional physical cross-linking point, but the breakable nature of the bonds and a broad distribution of distances between crosslinks may creates most likely a wide dissipative zone.