Condensation Of 3-glycidoxypropyltrimethoxysilane Research Articles

Chitosan-doped-hybrid/TiO2 nanocomposite based sol-gel coating for the corrosion resistance of aluminum metal in 3.5% NaCl medium

The study outlines the role of chitosan, a biopolymer on corrosion behavior of Hy/nano-TiO2 based sol-gel coating over aluminum metal. In this study organic-inorganic hybrid sols were synthesized through hydrolysis and condensation of 3-glycidoxypropyltrimethoxy silane (GPTMS), tetraethoxysilane (TEOS) and titanium (IV) isopropoxide (TIP) in acidic solution. Chitosan was doped into sol-gel matrix and self-assembled over aluminum substrate. The resultant chitosan-doped-Hy/nano-TiO2 sol-gel coating was characterized by Fourier Transform Infrared (FT-IR) spectra, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Energy-Dispersive X-ray Spectroscopy (EDX) analyses. The as-tailored aluminum substrate was evaluated for corrosion resistance in neutral medium. The protection ability of these coatings was evaluated by electrochemical impedance studies (EIS) and potentiodynamic polarization (PP) measurements in 3.5% NaCl medium. The EIS and PP results showed that chitosan-doped- Hy/nano-TiO2 sol-gel coating exhibited better protection from corrosion than the undoped Hy/TiO2 nanocomposite coating.

Effect of ceria and zirconia nanoparticles on mechanical behavior of nanocomposite hybrid coatings

Epoxy-silica based hybrid nanocomposite coatings have been developed with different organicinorganic contents by sol–gel process. Various ratios of ceria and zirconia colloidal dispersions as inorganic nanoparticles are uniformly distributed in the hybrid sol. The hybrid sols are prepared by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) in acidic solution using bisphenol A (BPA) and 1-methyl-imidazol (MI). A thin layer of each sol is coated on a micro-glass slide and 1050 aluminum alloy as substrates. The effect of alkoxysilane precursors (i.e. TEOS and GPTMS) and inorganic to organic molar ratio are investigated. Nanoindentation and dynamic mechanical analysis (DMA) performed to characterize the mechanical properties of the coatings in nanorange scale. It is revealed that all hybrid nanocomposite coatings had appropriate flexibility and strong interfacial interaction with the aluminum alloy substrate. It is proposed that the ceria and zirconia nanoparticles can be bonded to the surrounding of siloxane ring which can be induced high restriction in polymeric chain mobility in dynamic mechanical analysis. Nanoindentation tests showed that by increasing the inorganic phase in the nanocomposite, both elastic modulus and hardness increase, especially they are very intense in the higher levels of inorganic content.

Studies on the effects of thiourea and its derivatives doped—Hybrid/zirconium nanocomposite based sol-gel coating for the corrosion behaviour of aluminum metal

Abstract The present work examines the effects of thiourea and its derivatives on corrosion behaviour of hybrid/zirconium (Hy/Zr) nanocomposite based sol-gel coatings. The hybrid sols were prepared by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS), tetramethoxysilane (TMOS) and tetra- n -propoxyzirconium (TPOZ) in acidic solution. Thiourea (TU), N -phenylthiourea (PTU), N -methylthiourea (MTU) and N -allylthiourea (ATU) which act as networking agents were doped seperately into the Hy/nano-Zr sol and were self-assembled over aluminum substrates. Fourier transform infrared (FT-IR) spectra, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) analyses were employed to investigate structure and morphologies of various coatings. The corrosion protection ability of these sol-gel coatings were evaluated by electrochemical impedance studies (EIS) and potentiodynamic polarization (PP) measurements in 3.5% NaCl medium. The results showed that among the various thiourea derivatives, MTU-doped-Hy/Zr nanocomposite based sol-gel coating exhibited better corrosion protection than the undoped Hy/nano-Zr, TU-doped-Hy/Zr, PTU-doped-Hy/Zr and ATU-doped-Hy/Zr nanocomposite coatings. The enhanced corrosion protection was mainly due to the presence of Hy/nano-Zr particles and electron donating nature of MTU which lead to the formation of densely packed layer functioning as a significant physical barrier against the attack of corrosive ions over the aluminum metal surface.

Effect of ceria and zirconia nanoparticles on corrosion protection and viscoelastic behavior of hybrid coatings

Organic–inorganic hybrid nanocomposite coatings contain inorganic particles that are dispersed in organic phase in nanometric dimensions. Ceria and zirconia colloidal dispersions are uniformly distributed in the epoxy silica-based hybrid nanocomposite by sol–gel method and coated on 1050 aluminum alloy substrate with spin-coating technique. The hybrid sol is prepared by organic–inorganic precursors formed by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane and tetraethylorthosilicate (TEOS) in acidic solution using bisphenol A as networking agent and 1-methylimidazole as initiator in the presence of various ratios of ZrO2 and CeO2 colloidal nanoparticles. Particle size distribution, surface morphology and inorganic components distribution were determined by scanning electron microscopy (SEM) and EDXA techniques. SEM and Si, Zr, Ce mapping micrographs proved the uniform distribution of nanoparticles in the coatings. Transmission electron microscopy indicated that the nanoparticles dimension stay at the nanoscale level. The glass transition temperature (Tg) and loss properties (damping) of coatings were evaluated by dynamic mechanical thermal analysis. The corrosion protection of the coatings on the 1050 AA substrate was studied by potentiodynamic measurements. The results indicated that by introducing ceria nanoparticles in 1:1 molar ratio to TEOS in coating composition, corrosion protection was improved. However, the simultaneous presence of two nanoparticles (i.e., ceria and zirconia in 1:1 molar ratio) in the coating compositions increased the corrosion protection efficiency up to 99.8 %. The multiple glass transitions and shifting to higher and wide range of temperatures by adding ceria and zirconia nanoparticles indicated a better network interaction between inorganic nanoparticles and organic molecular chains which also led to better corrosion protection of the coating in this composition.

Synthesis and properties of LED-packaging epoxy resin toughened by a novel polysiloxane from hydrolysis and condensation

A novel polysiloxane (GxDy) containing a large number of epoxide groups and flexible segments was synthesized by hydrolysis and condensation of 3-glycidoxypropyl trimethoxysilane (GPTMS) and dimethyldiethoxylsilane (DMDES) to toughen the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ERL-4221). The chemical structures of GxDy (molar ratio of GPTMS to DMDES is x/y) were confirmed by Fourier transform infrared spectroscopy (FTIR), 29Si nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC), and G4D6 have the highest degree of branching. The thermal and mechanical properties, morphologies and transmittance of the cured epoxy resins were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile testing, fracture testing, SEM, and UV-vis spectroscopy. The Tg of the GxDy modified epoxy depends on the structure and addition content of GxDy. The TGA results under a N2 demonstrate that the thermal stability of the epoxy resin was improved by GxDy and the Si-(O-)3 from the GPTMS part forms silica more easily than the Si-(O-)2 from the DMDES part. The addition of 10 phr G4D6 resulted in greatly improved toughness, but maintained the transmittance of the epoxy resin. In addition the morphology of the fracture surfaces showed that GxDy can be dispersed homogeneously in the epoxy resin, and the toughening follows the pinning and crack tip bifurcation mechanism. In conclusion, GxDy can increase the toughness and thermal properties of the ERL-4221 system simultaneously, and maintain its transmittance. Therefore, GxDy can be used as a toughening agent for light emitting diode (LED)-packaging epoxy resins.

Corrosion behaviour of sol–gel coatings doped with cerium salts on 2024-T3 aluminum alloy

The corrosion behaviour of the sol–gel coatings doped with cerium chloride or cerium nitrate on 2024-T3 aluminum alloy was investigated by using electrochemical impedance spectroscopy (EIS) and immersion tests. The sol–gel matrix was obtained through hydrolysis, condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS), using diethylentriamine as curing agent. The results indicated that cerium nitrate with concentration of 1 × 10 −3 mol L −1 in the silane solution was excellent on self-healing for the sol–gel coating, while cerium chloride had no obvious effect. This result suggested that the introduction of Cl − promoted the under-film pitting of 2024-T3 substrate. It was found that Ce(OH) 3 and Ce(OH) 2 2+ simultaneously existed in the silane solution by X-ray diffraction (XRD) analysis. Ce(OH) 2 2+ transformed to CeO 2 due to high-temperature curing of sol–gel matrix demonstrated by X-ray photoelectron spectroscopy (XPS) analysis. Therefore, it can be considered that Ce(OH) 3 and CeO 2 played inhibition roles in the corrosion process of the sol–gel coatings.