Condensation Of Methyltriethoxysilane Research Articles

The preparation and properties of a transparent coating based on organic silicone resins

Purpose – The purpose of this investigation was to study a transparent coating based on organic silicone resins prepared by the hydrolysis and condensation of methyltriethoxysilane and tetraethoxysilane. Design/methodology/approach – The coating film was characterized by IR, UV, thermal gravity analysis, scanning electron microscope and an automatic contact angle meter. Some properties of the coating film, such as adhesion, impact resistance and wear-resistance also were evaluated. Findings – These uniform, clear and smooth coating films possessed the high transparent and light transmittance, high density, high hydrophobicity, good adhesion, hardness and anti-corrosion. Originality/value – The coating may be considered as a protective film for the surfaces of the metals and plastics.

Investigation of hydrolysis and condensation of methyltriethoxysilane in aqueous systems

An effective synthesis of methylethoxysilanes and emulsification of methyltriethoxysilane is described. Hydrolysis and condensation products of methyltriethoxysilane were identified and studied using 29 Si NMR, mass spectrometry and infrared spectroscopy. The presented analyses are important from practical point of view, as the emulsion in question is used for hydrophobization of building materials and soil. The most striking finding is high stability of the low molecular products of hydrolysis - methylsilanetriol [MeSi(OH) 3 ] and its dimer [(OH) 2 (Me)SiOSi(Me)(OH) 2 ]. All of which were still present in the aqueous medium, after 40 days of storage at ambient conditions. This finding suggests that condensation processes leading to the formation of polymer network are slow in the emulsion and a large number of reactive hydroxyl groups are present in the system allowing for the effective hydrophobization of mineral material.

Effective corrosion inhibition performance of Ce3+ doped sol–gel nanocomposite coating on aluminum alloy

Sol–gel nanocomposite coatings have been investigated for Alclad AA2024 as a potential replacement for the hazardous and banned hexavalent chromate conversion coatings. The sol–gel coatings were prepared using a sol obtained by the hydrolysis and condensation of methyltriethoxysilane and colloidal silica. They were doped with cerium nitrate inhibitor to provide active corrosion protection and were deposited by spray-coating method. The sol–gel process conditions were optimized to obtain smooth and homogenous crack free films. The chemical composition and microstructure of the coatings were studied using EDX and FESEM respectively. The effect of cerium nitrate concentration on the corrosion protection efficiency of the sol–gel coatings was evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy and salt spray tests. The results indicated that cerium nitrate doped coatings were more resistant to corrosion than undoped coating. The coatings doped with 6000ppm cerium nitrate rendered improved protection after longer immersions due to the inhibitive action of Ce3+.

Decorative, hydrophobic sol–gel coatings densified using near-infrared radiation

Decorative, hydrophobic coatings were generated using sols synthesized from hydrolysis and condensation of methyltriethoxy silane, tetraethoxy silane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane, in combination with nanosized and submicron-sized inorganic black pigment particles. Coatings were densified at 250 °C using near-infrared radiation as well as by a conventional curing method. The densified coatings were characterized for their thickness, roughness, contact angles and adhesion. The properties of the near-infrared radiation cured pigmented coatings were found to be comparable with those of the conventionally cured coatings. The pigmented coatings generated using nanosized pigments, whether near-infrared radiation cured or conventionally cured were seen to exhibit improved hydrophobicity with contact angles ranging from 130 to 145° when compared to their transparent unpigmented counterparts, that showed water contact angles from 93 to 97°. The improved hydrophobicity was explained on the basis of presence of a possible double length scale roughness of the coatings.

Curing Behavior and Thermal Properties of Me-SSQ/Cyanate Ester Resin Organic-Inorganic Hybrids

A kind of nonfunctional silsesquioxane (SSQ), methylsilsesquioxane (Me-SSQ), was used to modify cyanate ester resin (CE) in this paper. First, methylsilsesquioxane (Me-SSQ) was synthesized by the hydrolysis and condensation of methyltriethoxysilane. Then a series of Me-SSQ/CE hybrids containing 0wt%, 1wt%, 5wt%, 10wt% and 20wt% of Me-SSQ were prepared. The effect of Me-SSQ content on the curing behavior and thermal properties of materials was investigated by using Fourier transforms infrared (FT-IR) spectroscopy and thermogravimetry (TG), respectively. FT-IR results indicate that the addition of Me-SSQ does not show significant effect on the conversion of CE. However, TG data show that Me-SSQ improved the thermal properties of CE greatly.

Mechanical Properties and Micromorphologies of Methyl- Silsesquioxane/Cyanate Ester Resin Organic-Inorganic Hybrids

A kind of nonfunctional oligomeric silsesquioxane (SSQ), methylsilsesquioxane (Me-SSQ), was used to modify cyanate ester resin (CE) in this paper. First, Me-SSQ was synthesized by the hydrolysis and condensation of methyltriethoxysilane. Then a series of Me-SSQ/CE hybrids containing 0wt%, 1wt%, 5wt%, 10wt% and 20wt% of Me-SSQ were prepared. Curing reactivity of the hybrid materials was studied by differential scanning calorimetry (DSC). Mechanical properties of the Me-SSQ/CE hybrids were studied systematically. Impact strength of the Me-SSQ/CE hybrids reaches its maximum value when Me-SSQ content is 5wt%. However, the flexural strength reaches the maximum value when Me-SSQ content is 1wt%. SEM images accord well with the mechanical properties. It is concluded that appropriate amount of Me-SSQ is favorable to improve the mechanical properties of Me-SSQ/CE hybrid materials.

Methyl silsesquioxane/cyanate ester resin organic–inorganic hybrids with low dielectric constant

AbstractA kind of nonfunctional oligomeric silsesquioxane (SSQ), methyl silsesquioxane (Me‐SSQ), was used to modify cyanate ester (CE) resin in this article. First, Me‐SSQ was synthesized by the hydrolysis and condensation of methyltriethoxysilane. Then, a series of Me‐SSQ/CE hybrids containing 0, 1, 5, 10, and 20 wt % of Me‐SSQ were prepared. The effect of Me‐SSQ content on the reactivity, mechanical, dielectric, thermal, and hot/wet properties of materials was investigated. Fourier transform infrared spectroscopy was used to study the reactivity of hybrid CE resin systems, indicating that the addition of Me‐SSQ does not show significant effect on the conversion of CE. Mechanical and dielectric properties of the Me‐SSQ/CE hybrid materials were also studied. Impact strength of the Me‐SSQ/CE hybrids reaches its maximum value when Me‐SSQ content is 5 wt %. However, the flexural strength reaches the maximum value when Me‐SSQ content is 1 wt %. The Me‐SSQ/CE hybrid containing 20 wt % of Me‐SSQ shows a dielectric constant of 2.78, that is, much lower than the pure CE resin. At the same time, the dielectric loss of the Me‐SSQ/CE hybrids was slightly increased (tan δ < 0.006). Therefore, Me‐SSQ/CE hybrid is a promising candidate for high‐performance printed circuit board matrix materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Water‐resistant conducting hybrids from electrostatic interactions

AbstractConductive hybrids were prepared in a water/ethanol solution via the sol–gel process from an inorganic sol containing carboxyl groups and water‐borne conductive polyaniline (cPANI). The inorganic sol was prepared by the hydrolysis and condensation of methyltriethoxysilane with the condensed product of maleic anhydride and aminopropyltriethoxysilane as a catalyst, for which the carboxyl counterion along the cPANI backbone acted as an electrostatic‐interaction moiety. The existence of this electrostatic interaction could improve the compatibility of the two components and contribute to the homogeneous dispersion of cPANI in the silica phase. The electrostatic‐interaction hybrids displayed a conductivity percolation threshold as low as 1.1 wt % polyaniline in an emeraldine base, showing 2 orders of magnitude higher electrical conductivity than that without electrostatic interactions. The electrostatic‐interaction hybrids also showed good water resistance; the electrical conductivity with a cPANI loading of 16 wt % underwent a slight change after 14 days of soaking in water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1424–1431, 2007

The microstructure and anticorrosion performance of phytic acid-catalyzed polysilsesquioxane coatings

In this paper, the polysilsesquioxanes were prepared via the hydrolysis and condensation of methyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane and tetraethoxysilane under the catalysis of phytic acid for the first time. Their microstructure and corrosion resistant performance were investigated by 13C NMR, 29Si NMR, GPC, SEM, electrochemical techniques and salt spray test, respectively. It was found that phytic acid could catalyze the sol–gel reaction more efficiently than hydrochloric acid, causing more T3 structures, and the phytic acid-catalyzed polysilsesquioxane coatings had excellent corrosion resistance performance.

Optical oxygen sensing based on luminescence quenching of platinum porphyrin dyes doped in ormosil coatings

Organically modified sol–gel films (ormosils) doped with platinum porphyrin dyes were prepared by using acid-catalyzed hydrolysis and condensation of methyl triethoxysilane (MTEOS) as precursor. The process variables like water to precursor molar ratio, acid concentration and aging time of the acid-catalyzed MTEOS-based sol were controlled to obtain ormosil coatings with good sensor properties. The effect of dopant concentration on the oxygen sensitivity was studied. The photophysical properties and decay kinetics of the coatings were studied and compared. Stern–Volmer plots for both PtOEP- and PtTFPP-doped sensor coatings were linear. The oxygen sensitivities ( I 0/ I 100) of these sensor coatings were found to be about 28 and 50 for PtTFPP and PtOEP, respectively. The ormosil coatings doped with porphyrin dyes exhibited higher oxygen sensitivity and better photostability compared to other silicone-based sensor coatings. Hence they may have good potential for surface pressure measurements in aerodynamic applications.

Effect of Addition of MTES on the Structure of Siloxane-PPG Nanocomposites

Hybrid transparent and flexible siloxane-polypropyleneglycol (PPG) materials with covalent bonds between the inorganic (siloxane) and organic (polymeric) phases were prepared by sol-gel process. In order to improve the quality of the mechanical properties of these materials, different amounts of methyltriethoxysilane (MTES) were added to the initial sol. The effect of MTES addition on the structure of the composites was studied by Small-Angle X-Ray Scattering (SAXS) and 29Si Nuclear Magnetic Resonance (29Si NMR). In absence of MTES, SAXS spectra exhibit a peak that is assigned to spatial correlation due to short range order between the siloxane clusters embedded in the polymeric phase. The experimental results indicate that, for low MTES concentrations ([MTES]/[O] ≤ 0.8, O: ether-type oxygen of PPG), the silicon species resulting from hydrolysis and condensation of MTES fill the open spaces between polymeric chains, interacting with the ether-type oxygens. For larger MTES content ([MTES]/[O] ≥ 0.8), the number of “free” ether-type oxygen sites avalaible for reaction with such silicon species is not large enough. Consequently, a fraction of silicon species resulting from MTES addition graft to siloxane clusters formed by hydrolysis and condensation of the hybrid precursor. For all MTES concentrations the condensation degree of the siloxane phase, determined from 29Si NMR spectroscopy, is high (>69%), as expected under neutral pH synthesis conditions.

Preparation and properties of polyimide-polysiloxane hybrid materials by the sol-gel process

Polyimide-poly(methylsiloxane) hybrid films were successfully prepared by the sol-gel process with methyltriethoxysilane (MTES) and/or dimethyldiethoxysilane (DMDES) in the polymer solution. Two methods were used for making hybrid films. First, MTES and/or DMDES were dissolved in the N,N-dimethylacetamide (DMAc) solution of the polyamic acid (polyimide precursor) prepared from 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300°C the polyamic acid was converted to polyimide and the sol-gel reaction, which consists of hydrolysis and condensation of MTES and/or DMDES, proceeded simultaneously. Second, methanol was used as the solvent to make the hybrid films by using the triethylamine salt of polyamic acid. The IR spectra proved that the sol-gel reactions started from MTES and DMDES readily proceeded in the polymer matrix. The hybrid films prepared in methanol were more transparent than those prepared in DMAc. Measurement by dynamic mechanical analysis indicated that the polystloxane was dispersed homogeneously in the polyimide matrix even after the heat treatment at 300°C, in the case of both DMAc and methanol solution methods. With respect to the tensile properties, the tensile strength and the elongation at break of the hybrid films prepared by the methanol solution method were higher than those by the DMAc solution method. The modulus of the obtained hybrid films decreasing with increasing DMDES ratio in the silicone unit in both cases.