Concentration Of Vinyltriethoxysilane Research Articles

Designing Kappa-carrageenan/guar gum/polyvinyl alcohol-based pH-responsive silane-crosslinked hydrogels for controlled release of cephradine

Kappa-carrageenan (KC)/guar gum (GG)/poly(vinyl alcohol) (PVA)-based pH-sensitive hydrogels were prepared using silane as a crosslinker. Vinyltriethoxy silane (VTEOS) is a non-toxic and biocompatible in nature so, its influence on the physiochemical properties of synthesized KcGP hydrogel films was investigated by varying its concentration. Different swelling media like water, ionic, buffer solutions were used to find out the swelling results. With the increase in concentration of VTEOS, the swelling ratio decreased in water, whereas all hydrogels showed the maximum swelling in acidic media, low in basic and moderate swelling at neutral pH. Various characterization techniques like FTIR, SEM and TGA were performed to study the characteristic changes of native and crosslinked hydrogel films. Cephradine (model drug) was loaded on KcGP2 and studied its drug release pattern in phosphate buffer saline. The drug was released in a controlled way up to 85.5% in 120 min. Cytocompatibility test on 3T3 cells fibroblast cell line showed that these hydrogels are non-toxic and can be used not only for targeted as well as oral drug delivery but also for other biomedical applications.

Studies on Borosiloxane Oligomers from Mixtures of Vinyltriethoxysilane and Phenyltrialkoxysilanes

Polycondensation of boric acid (BA) with mixtures of phenyltriethoxysilane (PTEOS) and vinyltriethoxysilane (VTEOS) and with mixtures of phenyltrimethoxysilane (PTMOS) and vinyltriethoxysilane (VTEOS) in diglyme at 83–87 °C using HCl as catalyst resulted in vinyl-functionalized borosiloxane oligomers. Effect of variation of PTEOS:VTEOS and PTMOS:VTEOS ratio (keeping BA:alkoxysilanes ratio constant) and the effect of variation of BA:alkoxysilane (BA:PTEOS:VTEOS and BA:PTMOS:VTEOS) ratio on the solubility, thermal stability and ceramic residue were studied. The oligomers obtained were characterized by FTIR, GPC, pyrolysis GC and TGA. For PTEOS + VTEOS system all the oligomers were soluble in the reaction medium, but after removal of alcohol (byproduct) and diglyme (solvent), the oligomers obtained in the solid form were insoluble in common organic solvents. Unlike the PTEOS-based system, for PTMOS-based system the oligomers synthesized from monomer feed ratios (BA:PTMOS:VTEOS) 1:1:1 and 1:1.67:0.33 even after the removal of ethanol and diglyme are soluble in tetrahydrofuran, dioxane and diglyme. These two soluble oligomers show bimodal molecular weight distribution with $$\overline{{\text{M}}}_{{_{{\text{W}}} }}$$ of 3,650 and $${\overline{\text{M}}}_{{\text{n}}}$$ of 1860 for 1:1:1 mol ratio, and $$\overline{{\text{M}}}_{{_{{\text{W}}} }}$$ of 2,540 and $${\overline{\text{M}}}_{{\text{n}}}$$ of 1700 for 1:1.67:0.33 mol ratio. 29Si-NMR spectra of the soluble oligomers show peaks at − 69 and − 78 ppm which are attributed to T2 and T3 structures respectively. Thermogravimetric analysis of vinyl-functionalized borosiloxane oligomers from PTEOS and PTMOS indicates that the ceramic residue of the oligomers in argon atmosphere at 900 °C varies from 68 to 89% depending on the monomer feed ratio of BA to organoalkoxysilane ratio and phenyltrialkoxysilane to VTEOS ratio. With the increase in concentration of VTEOS in the monomer feed the thermal stability as well as the ceramic residue of the oligomers increase and a reverse trend is observed for variation of BA concentration. Pyrolysis of the oligomers produce C2, C3 hydrocarbons and benzene as the main pyrolysis products. Ceramic conversion of a typical oligomer was carried out at 900 °C, 1500 °C and 1650 °C in argon atmosphere. The ceramics obtained at 900 °C and 1500 °C are amorphous SiBOC which transform to β-SiC at 1650 °C.

Surface modification of zinc oxide nanoparticles by vinyltriethoxy silane (VTES)

Zinc oxide (ZnO) nanoparticles are hydrophilic in nature and difficult to disperse in polymer matrix due to agglomeration behavior. To disperse the zinc oxide nanoparticles in polymer matrix, it is necessary to modify their surface with hydrophobic groups such as silanes or surfactants. In this article, zinc oxide nanoparticles were modified with various concentration of vinyl triethoxysilane (VTES). To investigate the effect of different concentrations of VTES, on surface modification of zinc oxide nanoparticles, these were characterized using physical characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), Energy Dispersive X-rays Spectroscopy (EDX), X-ray diffraction (XRD) and contact angle. The results of FTIR, TGA, SEM, EDX and contact angle confirm the surface modification of zinc oxide nanoparticles by VTES. The XRD results show that the crystalline behavior of ZnO nanoparticles was not changed after surface modification by VTES. The crystallite size of surface modified ZnO nanoparticles was calculated using Debye-Scherrer equation and it was found approx 20 nm. In FTIR results, some new peaks at 1409, 1014 and 970 cm−1 were observed as compare to unmodified zinc oxide nanoparticles. In contact angle analysis, it was observed that the surface modified zinc oxide nanoparticles have very high contact angle (greater than150°) in comparison with hydrophilic behavior of unmodified zinc oxide nanoparticles. SEM analysis also showed the improved dispersity of ZnO nanoparticles. Based on characterization results, it was observed that the 15 wt% VTES concentration is suitable to carry out surface modification of ZnO nanoparticles.

Composite Fibers Based on Cellulose and Vinyltriethoxysilane as Precursors of Carbon Materials

A new method is developed for the production of composite fibers based on cellulose and vinyltriethoxysilane and formed from N-methylmorpholine-N-oxide solutions. Introduction of the organosilicon additive promotes the activation of cellulose pyrolysis processes, and its choice relies on the presence of a double bond in vinyltriethoxysilane, which can be opened when the temperature rises. Mixed solutions are emulsions with labile droplets of the organosilicon liquid that easily change their shape under deformation. The study of the rheological behavior of the mixed solutions of cellulose with vinyltriethoxysilane reveals an unusual character of a change in viscosity with the concentration of vinyltriethoxysilane—with a minimum at 10–15%. From joint solutions by the dry-jet wet method, composite fibers are spun in an aqueous coagulation bath at a rate of 50–70 m/min. The study of their thermal properties shows that in thermolysis vinyltriethoxysilane additives catalyze condensation processes in cellulose and lead to an increase in char yield. Using IR spectroscopy, the combined chemical transformations of cellulose and vinyltriethoxysilane at all stages of the heat treatment of composite fibers up to 1200°C are analyzed for the first time. It is found that during thermolysis the chemical interaction of vinyltriethoxysilane with cellulose occurs and carbon fibers “crosslinked” by silicon carbide fragments are formed.

Formation of an in situ nanosilica nanomatrix via graft copolymerization of vinyltriethoxysilane onto natural rubber

Natural rubber (NR) with an in situ nanosilica nanomatrix was characterized in present work. The in situ nanosilica nanomatrix was prepared via graft copolymerization of a silane monomer, vinyltriethoxysilane (VTES), onto deproteinized NR (DPNR) in latex stage using tetrapentamine (TEPA)/tert‐butylhydroperoxide (TBHPO) as initiators. VTES conversion of more than 80% was obtained, and it depended on VTES concentration. The graft copolymer structure was characterized by Fourier transform infrared (FT‐IR), solution‐state proton nuclear magnetic resonance (1H‐NMR), and solid‐state 29Si‐NMR spectroscopy. FT‐IR analysis of the graft copolymer confirmed the formation of in situ silica particles, while solution‐state 1H‐NMR and solid‐state 29Si‐NMR revealed the partial hydrolysis of the ethoxy groups and polycondensation of the silanol groups. The formation of nanosilica particles enhanced thermal and mechanical properties of the graft copolymer. Morphology observations of the in situ nanosilica nanomatrix through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the spherical nanosilica particles form a nanomatrix surrounding NR particle. The formation of the nanomatrix was proved to enhance mechanical properties for NR materials.

Free‐radical emulsion copolymerization of styrene with butadiene and vinyl triethoxysilane with a cumene hydroperoxide redox initiator

ABSTRACTThe emulsion free‐radical copolymerization of vinyl triethoxysilane (VTES) with styrene (St) and butadiene (Bd) was initiated by cumene hydroperoxide and ferrous sulfate at 0 °C. The effects of VTES on the copolymerization conversion, reaction time, gel content, latex particle size, thermal stability, and mechanical properties were thoroughly investigated. The success of this reaction was confirmed by the peaks attributed to both Si─O─Si groups at 1065 cm−1 and the Si─O─C bond at 1046 cm−1. A kinetics analysis showed that the conversion decreased with increasing VTES mass in the monomer feed. Compared with that in the St–Bd copolymer, the latex particle size increased slightly with increasing VTES mass. The Mooney viscosity and gel content results show that a large fraction of precrosslinking molecular chains was formed in the rubber particles. The thermogravimetric analysis results indicate that the thermal stability of the copolymers increased with increasing VTES concentration. The 300% modulus and tensile strength of the St–Bd–VTES copolymer increased with the mass of VTES at first and then decreased after 3 phr VTES, whereas the elongation at break decreased with increasing VTES mass. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47896.

Monitoring the formation of polystyrene/silica nanocomposites from vinyl triethoxysilane containing copolymers

Random copolymers of polystyrene-co-polyvinyl triethoxysilane (PS-co-PVTES) were prepared via semi-batch emulsion polymerization with different feed monomer compositions and evaluated as precursors of polystyrene (PS)/silica nanocomposites. Small-angle X-ray scattering (SAXS) profiles acquired from 20 °C to 180 °C showed that, at temperatures higher than glass transition temperature (Tg) of PS, the latex particles aggregate. On thermal annealing at 180 °C, silica-rich domains are formed, as corroborated by scanning electron microscopy. Infrared spectroscopy and differential scanning calorimetry analyses showed a reduction of the silanol concentration and an increase in the Tg value, respectively. The silica long domain spacing, measured by SAXS, depends on the concentration of vinyl triethoxysilane (VTES) in the feed; this value varied from 35 to 57 nm when the weight ratio of the monomers (styrene/VTES) was 50:50 and 90:10, respectively.

Preparation and Characterization of Highly Monodisperse Vinyl Functionalized Silica Spheres by Sol-Gel Method

Highly monodisperse and uniform-size vinyl functiona-lized silica spheres were synthesized directly from vinyltriethoxysilane (VTES) in water/ethanol mixed solution, and in this system, we successfully controlled the size and shape of hybrid silica spheres by adjusting the concentrations of the precursor VTES and catalyst ammonia. On the basis of the experiment results, it was found that hybrid spheres size significantly increased as the increment of concentration of VTES. However, increasing ammonia concentration resulted in decreasing of diameter of hybrid silica spheres from 542 to 272 nm. The morphologies and structure were determined by Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier transformed infrared (FT-IR).

Surface Analysis and Electrochemical Behavior of Aluminum Pretreated by Vinyltriethoxysilane Films in Mild NaCl Solution

Electrochemical characteristics, composition and surface morphology of vinyltriethoxysilane (VTES) coatings on aluminum were investigated. The silane coatings were deposited chemically, by immersion in 2 and 5% VTES, and then cured at 100°C during 10 or 30 min. Surface morphology of VTES films was analyzed by scanning electron microscopy, while the composition was investigated by X-ray photoelectron spectroscopy. The corrosion stability of silane coatings was determined by electrochemical impedance spectroscopy in 0.03% NaCl. The results obtained were compared with the standardized analysis in the salt spray chamber. The percentage of the corroded area was determined by optical microscopy coupled with image analysis. The influence of VTES concentration and curing time on the corrosion stability of silane films on aluminum was shown. The highest corrosion stability was obtained for silane films deposited from 5% VTES solution with 30 min curing, while the lowest stability was determined for silane films deposited from 2% VTES solution with 10 min curing. Surface analysis suggests that the coatings with the highest corrosion stability are related to the intensive siloxane bonding (Si–O–Si), which is favored by deposition from more concentrated VTES solution.

Surface Topography of Vinyltriethoxysilane Films Deposited on the Silicon Dioxide Substrate (0001) Investigated by Atomic Force Microscopy

The surface topography and growth behavior of self-assembled monolayers (SAMs) formed from vinyltriethoxysilane (VTES) at a constant temperature (20°C) on silicon dioxide substrates were investigated using atomic force microscopy (AFM). Two methods for silanization were introduced: vapor phase deposition and deposition from a solution. The influence of deposition conditions on the topography of silane films was also studied. The property of modified SiO2 substrates surface was characterized by static water contact angle measurements. The experimental results revealed that the silane films deposited from the solution method grew via islands, whereas this is not the case for vapor phase deposition. The roughness of the layers deposited via solution method first decreased and then increased with the VTES concentration increasing, while the roughness of the layers deposited via vapor phase increased straight. Furthermore, the adsorption types for silane being adsorbed on SiO2 substrates were also investigated. The results indicated that there were two adsorption types in both deposition processes: physisorption and chemisorption.

Studies on preparation and properties of vinyltriethoxysilane-grafted styrene-butadiene rubber

Graft polymerization of vinyltriethoxysilane (VTES) onto styrene-butadiene rubber (SBR) was carried out in latex using benzoic peroxide (BPO) as an initiator. The concentration of VTES effecting on vulcanization characteristics, mechanical properties and thermal properties of VTES-grafted SBR (SBR-g-VTES) were investigated. The grafting of VTES onto SBR and its pre-crosslinking were confirmed by attenuated total teflectance-Fourier transform infrared reflectance and proton nuclear magnetic resonance. The mechanism of graft polymerization was studied. The results revealed that the minimum torque, optimum cure time, tensile strength, thermal decomposition temperature, and glass transition temperature (Tg) all increased with the increasing concentration of VTES. But the grafting efficiency of VTES, rate of vulcanization, and elongation at break of the SBR-g-VTES decreased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Three dimensional image analysis for prediction of vinyl triethoxysilane concentration and porosity percent of methyl methacrylate/ethylene glycol dimethacrylate copolymers using scanning electron microscopy

In this work, scanning electron micrographs of copolymer beads based on methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM) and vinyl triethoxysilane (VTES) were used to construct multivariate image regression models. Scanning electron microscopy (SEM) and swelling measurements indicated that increasing the silicone concentration (VTES) of the copolymers enhances the amount of pores and porosity percent. Scanning electron micrographs of the synthesized copolymers with different VTES concentrations were used to construct two soft models, which were able to relate the VTES concentration and the porosity percent of the copolymers with their SEM images. The constructed models were the three-way partial least squares analysis (N-PLS) and unfolded principal component regression (unfold-PCR). The predictive ability of the constructed models were evaluated by a test set. The results showed the models were able to effectively predict the VTES concentration and the porosity percent of the copolymers using their corresponding SEM images.

Film blowing of silane‐modified polyethylene

AbstractThe grafting of vinyltriethoxysilane (VTES) onto polyethylene (PE) with the help of small amounts of peroxides was investigated to film‐blow these modified materials. The degree of crosslinking was kept very low to achieve good melt processability and improved mechanical properties. The possibility of obtaining modified PE films with improved properties and regularly distributed crosslinking with a single processing step demonstrates the uniqueness of this study. The additive concentration was established through preliminary studies; with a batch mixer, it was possible to process the modified PE in the film‐blowing operation. Water treatment of the modified films after film blowing allowed for improved properties without the processability being affected. The modification of PE was followed with mechanical, rheological, and extraction tests and with calorimetric analyses. The variations of the main mechanical properties of the films were very important from an application point of view. The elastic modulus and tear strength of the films for both extrusion directions (machine and transverse) increased with the VTES concentration increasing and even more with the addition of a small quantity of a peroxide. Some reductions of the tensile strength and elongation at break were observed, but these reductions were not considerable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Modified Polyacrylate‐Based Latexes Containing Silicone

Modified polyacrylate‐based latexes containing silicone were prepared by the emulsion copolymerization of three acrylic monomers [methyl methacrylate (MMA), n‐butyl acrylate (BA), and acrylic acid (AA)] and vinyl triethoxysilane (VTS), using disodium ethoxyhydrasulfosuccinate (A‐102) as the emulsifier and potassium persulfate as the initiator. The effects of the concentrations of A‐102, K2S2O8, VTS and the effects of reaction temperature on the total monomer conversion (%C) and the polymerization rate (R p) were investigated. It was found that the R p is proportional to the concentrations of A‐102 and K2S2O8 raised to the power of 0.35 and 0.48, respectively, while inversely proportional to the concentration of VTS raised to the power of 0.64. The overall activation energy of the emulsion polymerization was estimated to be 81.09 kJ/mol. Infrared spectroscopy (IR) and differential scanning calorimetry (DSC) analyses confirmed the modification reaction. For the modified polyacrylate latex prepared in the presence of 0.402 mol/L VTS, the spherical latex particles are fairly monodispersed and have an average diameter of 95.29 nm. The VTS amount has a great influence on the properties of the resulting latexes and their corresponding films. When compared with the pure polyacrylate latex, the modified polyacrylate‐based latexes containing silicone are characteristic of lower surface tension and better film properties such as lower water adsorption and enhanced thermal stability.

Gamma-rays induced copolymerization of vinyl triethoxy silane and methyl methacrylate: Their spectroscopic characterization

The γ-ray–induced copolymerization of vinyl triethoxy silane (VTES) with methyl methacrylate (MMA) was developed to be used in the simultaneous preservation and consolidation of archeological artifacts. A detailed analysis was performed to characterize the copolymerization reaction and conversion. The copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), and elemental analysis techniques. The mol fraction of VTES units in the synthesized copolymers were determined by elemental analysis of silicone pertaining to VTES segments using inductive coupling plasma spectroscopy (ICP). The effect of VTES mol fraction in the initial feed and the irradiation dose (6.5, 8.5, 10.0 kGy) on the yield of copolymerization was investigated. The yield of the copolymerization was found to decrease with increasing the VTES mol fraction in the monomer feed, and to increase with increasing the irradiation dose at each monomer composition. However, using the data obtained from the ICP measurements, the mol fraction of the VTES units in synthesized copolymers was determined to increase with increasing the VTES concentration in the initial monomer feed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 141–147, 1999

Curing characteristics and mechanical properties of vinyltriethoxysilane-coupled carbon black/styrene-butadiene rubber vulcanizates

Styrene–butadiene rubber (SBR) vulcanizates containing 0 to 2.73 parts of vinyltriethoxysilane (VTEOS) per hundred parts of rubber (phr) were prepared, keeping the other ingredients weight constant. The mixes were tested for their curing behavior by a curemeter. The vulcanizates were analyzed through a Universal tensile tester, fatigue-to-failure tester, and scanning electron microscope mainly for mechanical properties and correlation. An increase in induction time and decrease in cure time, each by 10%, was noticed by the incorporation of 2.73 phr of VTEOS. The tensile strength and elongation at break improved significantly up to 0.5 phr of VTEOS and either a small improvement or deterioration of these properties was observed beyond this concentration of VTEOS. The fatigue-to-failure cycle at four extension ratios showed a gradual and appreciable improvement. It is noteworthy to mention that the vulcanizate containing 2.73 phr VTEOS possessed about a threefold increase in the fatigue-to-failure cycle compared to its non-VTEOS vulcanizate. However, this distinction of the fatigue-to-failure cycle progressively decreased with increase in the extension ratios. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1719–1725, 1998