Preparation and anticorrosive properties of hybrid coatings based on epoxy‐silica hybrid materials

A series of sol‐gel derived organic–inorganic hybrid coatings consisting of organic epoxy resin and inorganic silica were successfully synthesized through sol‐gel approach by using 3‐glycidoxypropyl‐trimethoxysilane as coupling agent. Transparent organic–inorganic hybrid sol‐gel coatings with different contents of silica were always achieved. The hybrid sol‐gel coatings with low silica loading on cold‐rolled steel coupons were found much superior improvement in anticorrosion efficiently. The as‐synthesized hybrid sol‐gel materials were characterized by Fourier‐transformation infrared spectroscopy, ²⁹Si‐nuclear magnetic resonance spectroscopy and transmission electron microscopy. Effects of the material composition of epoxy resins along with hybrid materials on the thermal stability, Viscoelasticity properties and surface morphology were also studied, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nanocomposite coatings via simultaneous organic–inorganic photo‐induced polymerization: synthesis,structural investigation and mechanical characterization

Hybrid sol–gel films were prepared via a simultaneous organic‐inorganic UV‐curing process using a diaryliodonium salt as a superacid photogenerator. In this single‐step procedure, an epoxy functionalized reactive resin mixed with a variable amount of either of two epoxy trialkoxysilane precursors was UV‐irradiated, causing both the initiation of epoxy ring‐opening copolymerization and the catalysis of trialkoxysilyl sol–gel reactions. The concomitant photo‐induced sol–gel process was found to have a significant effect on the two related propagation mechanisms in competition for the oxirane ring‐opening—the active chain‐end and the activated monomer mechanisms—as proved by a systematic examination of the hybrid material microstructure through ²⁹Si and ¹³C solid‐state NMR spectroscopy. The effect of the oxo‐silica network generation on the epoxy reaction kinetics was also evaluated using real‐time Fourier transform infrared spectroscopy upon varying the epoxysilane structure and its concentration. Thermal and dynamic mechanical analyses were systematically performed on these hybrids, by studying thoroughly their structure–property interdependence. Other mechanical characterizations through tribological and scratch tests suggested that the present photopolymer–silica hybrid material provides a powerful tool to tailor mechanical property profiles. Copyright © 2010 Society of Chemical Industry     

Elaboration and mechanical characterization of nanocomposites thin films: Part I: Determination of the mechanical properties of thin films prepared by in situ polymerisation of tetraethoxysilane in poly(methyl methacrylate)

The sol–gel process allows to design hybrid organic–inorganic materials constituted by organic molecules or macromolecules and inorganic metal oxo-polymers interpenetrated at the nanometer scale. These hybrids were deposited as functional coatings with tunable thickness on float glass substrates. Good adhesion and mechanical behaviour of the coatings are required to keep their functionality in time hence; the performance of the PMMA-SiO₂ based thin films was investigated using nanoindentation. This study validates nanoindentation measurements as an appropriate technique to characterize hybrid organic–inorganic thin films, despite visco-elastic behaviours. Specific analysis procedures and the use of appropriate models allowed us to determine the indentation modulus and hardness of the hybrid layers reproductively. The structure and the mechanical behaviour are reported for thin films as a function of the fraction of silica.     

Study the factors affecting the performance of organic–inorganic hybrid coatings

In this article, a series of hybrid organic–inorganic coatings based on silica‐epoxy composite resins were prepared with the sol‐gel method by using γ‐aminopropyl triethoxysilane as a coupling agent. Especially, the research emphasized on the factors that influenced on the properties of the prepared hybrid coatings. Firstly, epoxy resin was reacted with γ‐aminopropyl triethoxysilane at a specific feeding molar ratio; subsequently, the asprepared sol–gel precursor was cohydrolyzed with tetraethoxysilane (TEOS) at various contents to afford chemical bondings to form silica networks and give a series of organic–inorganic hybrid coatings. They were loaded and cured on steel panels and characterized for FTIR, TGA, DSC, water contact angles (WCA), pencil hardness, surface & three‐dimensional morphological studies, and potentiodynamic polarization tests. The surfaces of the hybrid coatings showed Sea‐Island or Inverting Sea‐Island morphologies at a certain relative content of two components, which made the coatings possess hydrophobic property. Due to the contribution of organic and inorganic components, the prepared hybrid coatings possess a lot of properties such as pencil hardness, thermotolerance, and corrosion resistance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41010.     

Dual‐curable unsaturated polyester inorganic/organic hybrid films

An unsaturated polyester, based on maleic anhydride, 1,6‐hexanediol, and trimethylol propane, was formulated with tetraethylorthosilicate (TEOS) oligomers and a coupling agent to prepare inorganic/organic hybrid films. TEOS oligomers were prepared through the hydrolysis and condensation of TEOS with water, and 3‐(triethoxysilyl)propylisocyanate was used as the coupling agent between the organic and inorganic phases. The hybrid materials were cured by moisture via sol–gel chemistry and by the UV curing of unsaturated polyesters. To compare the properties of the moisture‐cured inorganic/organic hybrid films, a conventional 2K polyurethane system was also prepared. The tensile, adhesion, abrasion, and fracture toughness properties were investigated as functions of the coupling agent and relative amount of UV cure versus thermal cure. Although no difference could be observed in the tensile properties, the abrasion resistance, fracture toughness, and adhesion were enhanced by the incorporation of TEOS oligomers into polyurethane films. Also, the abrasion resistance, fracture toughness, and tensile properties were increased with both moisture and UV exposure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 115–126, 2006     

Synthesis and properties of PMMA‐ZrO2 organic–inorganic hybrid films

In this work we report the synthesis process and properties of PMMA‐ZrO₂ organic–inorganic hybrid films. The hybrid films were deposited by a modified sol‐gel process using zirconium propoxide (ZP) as the inorganic (zirconia) source, methyl methacrylate (MMA) as the organic source, and 3‐trimetoxy‐silyl‐propyl‐methacrylate (TMSPM) as the coupling agent between organic and inorganic phases. The films were deposited by dip coating on glass slide substrates from a hybrid precursor solution containing the three precursors with molar ratio 1 : 0.25 : 0.25 for ZP, TMSPM, and MMA, respectively. After deposition, the hybrid thin films were heat‐treated at 100°C for 24 h. The macroscopic characteristics of the hybrid films such as high homogeneity and high optical transparence evidenced the formation of a cross‐linked, interpenetrated organic–inorganic network. The deposited PMMA‐ZrO₂ hybrid films were homogeneous, highly transparent and very well adhered to substrates. Fourier Transform Infra‐Red measurements of the hybrid films display absorption bands of chemical groups associated with both PMMA and ZrO₂ phases. The amounts of organic and inorganic phases in the hybrid films were determined from thermogravimetric measurements. The surface morphology and homogeneity of the hybrid films at microscopic level were analyzed by scanning electron microscopy and atomic force microscopy images. From the analysis of optical transmission and reflection spectra, the optical constants (refraction index and extinction coefficient) of the hybrid films were determined, employing a physical model to simulate the hybrid optical layers. The refraction index of the hybrid films at 532 nm was 1.56. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42738.     

Synthesis and characterization of flame retarding UV‐curable organic–inorganic hybrid coatings

UV‐curable, organic–inorganic hybrid materials were synthesized via sol–gel reactions for tetraethylorthosilicate, and methacryloxypropyl trimethoxysilane in the presence of the acrylated phenylphosphine oxide resin (APPO) and a bisphenol‐A‐based epoxy acrylate resin. The sol–gel precursor content in the hybrid coatings was varied from 0 to 30 wt %. The adhesion, flexibility, and hardness of the coatings were characterized. The influences of the amounts of inorganic component incorporated into the coatings were studied. Results from the mechanical measurements show that the properties of hybrid coatings improve with the increase in sol–gel precursor content. In addition, thermal properties of the hybrids were studied by thermogravimetric analysis in air atmosphere. The char yield of pure organic coating was 32% and that of 30 wt % silicate containing hybrid coating was 30% at 500°C in air atmosphere. This result demonstrates the pronounced effect of APPO on the flame retardance of coatings. Gas chromatography/mass spectrometry analyses showed that the initial weight loss obtained in thermogravimetric analysis is due to the degradation products of the photoinitator and the reactive diluent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1906–1914, 2006     

Stabilized dispersions of titania nanoparticles via a sol–gel process and applications in UV‐curable hybrid systems

Organic–inorganic hybrid UV‐curable coatings were synthesized through blending UV‐curable components and stabilized titania sol prepared via a sol–gel process of tetrabutyl titanate (TBT) with three different stabilizers, acetylacetone (Acac), isopropyl tri(dioctyl)pyrophosphato titanate coupling agent (TTPO) and a polymerizable organic phosphoric acid (MAP). The size and the dispersion of titania particle in the UV‐cured organic matrix were dominated by the properties of these stabilizers. A cured hybrid film with titania particle size around 20 nm was obtained when TTPO was utilized as protection agent for the sol. It is interesting that the hardness and flexibility of the photocured hybrid films were improved simultaneously, in contrast to results with neat organic UV‐curable formulations. Copyright © 2006 Society of Chemical Industry     

Hybrid organosiloxane coatings containing epoxide precursors for protecting mild steel against corrosion in a saline medium

Hybrid organic–inorganic materials made from sol–gel precursors can be used as anticorrosion barriers on metal substrates. The modification of epoxy resins with silicones is an interesting approach toward the synthesis of hybrid materials that combine the advantages offered by epoxy resins with those of silicones. In this study, novel hybrid epoxy‐silicon materials were synthesized using sol–gel chemistry and subsequently functionalized with 4,4′‐methylenebis(phenyl isocyanate), incorporating urethane functionality into the final polymer. The study screened five different epoxide precursors for use in the synthesis of the new hybrid materials and optimizing their anticorrosion properties. Spectral characterization confirms the proposed chemical structures of the newly synthesized polymers. The newly developed polymers were painted on mild steel panels, thermally cured, and their thermal, surface morphological, adhesion, and anticorrosion properties were fully characterized. The new coatings were found to have excellent thermal stability and adherence properties to steel surface. The results of corrosion testing on coated steel panels following long‐term immersion in a 3.5 wt % aqueous NaCl medium revealed that the polymer prepared using the epoxide precursor bisphenol A diglycidyl ether provided the best anticorrosion protection property among the synthesized polymers. This could be attributed to the excellent integrity and crosslink density properties in addition to the lack of microdefects in the surface of this coated sample as confirmed by scanning electron microscopy analyses. The newly prepared hybrid coatings reported in this study are very promising as an alternative to toxic chromate‐based coatings. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43947.     

Characterization of antireflective coatings on poly(methyl methacrylate) substrate by different process parameters

The high/low refractive index organic/inorganic antireflective (AR) hybrid polymers were formed using the sol–gel process, in which TiO₂/2‐hydroxyethyl methacrylate (2‐HEMA) (high refractive index hybrid polymer) and SiO₂/2‐HEMA (low refractive index hybrid polymer) two‐layer thin films were formed on a hard coating deposited poly(methyl methacrylate) (HC‐PMMA) substrate by both spin coating and dip coating. The relationship between the process parameters and the optical properties, thickness, porosity, surface morphology, and adhesion was determined. The results show that the reflectance of the two‐layer thin films on HC‐PMMA substrate is less than 0.21% (λ = 550 nm), with good adhesion (5B) and a hardness of up to 4H. In addition, the thickness, porosity, and roughness of the films affect refractive index and the antireflection properties of the AR two‐layered thin film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,characterization, and properties of novel organic/inorganic epoxy hybrids containing nitrogen/silicon via the sol–gel method

Organic–inorganic hybrids were prepared with a diglycidyl ether of bisphenol A (DGEBA) type epoxy and silane‐modified isocyanuric acid triglycidyl ester via the sol–gel process. The DGEBA‐type epoxy was modified by a coupling agent to improve the compatibility of the organic and inorganic phases. The sol–gel technique was used successfully to incorporate silicon and nitrogen into the network of hybrids, increasing the thermal stability. Fourier transform infrared and ²⁹Si‐NMR were used to characterize the structures of the hybrids. The results revealed that trisubstituted siloxane bonds (T 3 ) was the major environment forming a network structure. The morphology of the ceramer was examined with scanning electron microscopy, Si mapping, and transmission electron microscopy. The particle sizes were less than 100 nm. The hybrids were nanocomposites. The ultraviolet–visible spectra of the epoxy hybrid showed no obvious absorbance over a range of 400–800 nm. This phenomenon revealed that the hybrids were transparent. The thermogravimetric analysis revealed that the char yields of the hybrids increased with the contents of the inorganic components. The integral procedure decomposition temperatures of the hybrids were higher than that of the pure epoxy. The thermal stability of the hybrids increased with the contents of the inorganic components. The inorganic components could improve the thermal stability of the pure epoxy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Greener Chemistry for Hybrid Materials,Alcohol‐Free Synthesis with an Epoxy‐Cyclohexyl Precursor

Green synthesis is one of the hot topics in the chemistry of hybrid organic–inorganic materials. A alcohol‐free sol–gel process has been developed to prepare optically transparent hybrid films from an epoxy bearing alkoxide, [2‐(3,4‐epoxy‐cyclohexyl)‐ethyl]‐trimethoxysilane (ECTMS). The synthesis is simple and effective because only two components, ECTMS and an aqueous solution of NaOH, are employed. Infrared spectroscopy has been used to monitor the reactivity of the precursor sol as a function of the aging time. Organic–inorganic hybrid films have been then prepared with the different sols via spin‐coating. The presence of the cyclohexyl ring slows down dramatically both the epoxide opening and the capability of the resulting diols in forming a tricyclic dioxane derivative. The highly basic conditions employed in the synthesis favor the formation of the cyclohexyl rings and cage‐ and ladder‐like silica structures. The hybrid films have shown a high transmittance in the visible range and a thermal stability up to 200 °C.

     

Structure–property relationship in epoxy‐silica hybrid nanocomposites: The role of organic solvent in achieving silica domains

The thermo‐mechanical properties of a series of epoxy‐silica hybrid composites prepared through sol–gel process are evaluated in a manner that the effect of organic solvent on the formation of silica domains is highlighted. By means of infrared spectroscopy, small‐angle X‐ray scattering, scanning electron microscope, dynamic mechanical thermal analysis, and thermo‐gravimetric analyzer, the specimens were morphologically studied varying the type of organic solvent. Among polar and nonpolar solvents incorporated by the organic–inorganic hybrid system, a mixture of xylene and ethanol (3:1) was properly comparable with tetrahydrofuran (THF) solvent regarding appearance and thermo‐mechanical characteristics. Enhanced thermal stability and modulus was observed upon increasing solvent content. Also, a proper dispersion of silica domains throughout the epoxy was seen in the case that the xylene/ethanol mixture or THF served as solvent. It is to be emphasized that the assigned mixture is environmentally better than that of THF. J. VINYL ADDIT. TECHNOL., 21:305–313, 2015. © 2014 Society of Plastics Engineers     

Organic–inorganic hybrid materials derived from epoxy resin and polysiloxanes: Synthesis and characterization

In this study, hybrid materials based on epoxy resin were prepared as transparent self‐supported films by a sol–gel process. 4,4′‐Diaminodiphenylmethane or oligomeric epoxy resin were used as precursors, which were conveniently functionalized with trialkoxysilanes as end‐groups. The effect of the introduction of poly (dimethylsiloxane) was also investigated. The hybrid films showed good thermal stability, a nondefined glass transition temperature, and a dense morphology without phase segregation. The tendency to a flat surface could be observed by atomic force microscopy. The hybrid films also showed good performance as coatings for glass plates, with an improved hydrophobic character in comparison to neat epoxy resin. POLYM. ENG. SCI., 48:141–148, 2008. © 2007 Society of Plastics Engineers     

Electrochemical investigations on the corrosion protection effect of poly(vinyl carbazole)‐silica hybrid sol–gel materials

A series of sol–gel derived organic–inorganic hybrid coatings consisting of organic poly (vinyl carbazole) (PVK) and inorganic silica (SiO₂), with 3‐(trimethoxysilyl)propyl methacrylate (MSMA) as coupling agent, were successfully synthesized. First of all, vinyl carbazole (VCz) monomers are copolymerized with MSMA by performing free‐radical polymerization reactions with AIBN as initiator. Subsequently, as‐prepared copolymer (i.e., sol–gel precursor) was further reacted with various feeding content of tetraethyl orthosilicate (TEOS) through organic acid (CSA)‐catalyzed sol–gel reaction to form a series of PVK‐silica hybrid (PSH) sol–gel materials. The as‐synthesized hybrid materials were subsequently characterized by Fourier‐Transformation infrared (FTIR) spectroscopy and solid‐state ²⁹Si NMR. It should be noted that the PVK‐SiO₂ hybrid (PSH) coating on cold‐rolled steel (CRS) electrode with low silica loading (e.g., 10 phr) was found to be superior in anticorrosion property over those of neat PVK based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current, and electrochemical impedance spectroscopy in 3.5 wt% NaCl electrolyte. The better anticorrosion performance of PSH coatings as compared to that of neat polymer may probably be attributed to the stronger adhesion strength of PSH coatings on CRS electrode, which was further evidenced by Scotch tape test evaluation. Increase of adhesion strength of PSH coatings on CRS electrode may be associated with the formation of Fe–O–Si covalent bonds at the interface of PSH coating and CRS electrode based on the FTIR–RAS (reflection absorption spectroscopy) studies. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Thermal and optical properties of PMMA–titania hybrid materials prepared by sol‐gel approach with HEMA as coupling agent

A series of sol‐gel derived organic–inorganic hybrid materials consisting of organic poly(methyl methacrylate) (PMMA) and inorganic titania (TiO₂) were successfully synthesized by using 2‐hydroxyethyl methacrylate (HEMA) as coupling agent. In this work, HEMA is first copolymerized with methyl methacrylate monomer at specific feeding ratios by using benzoyl peroxide (BPO) as initiator. Subsequently, the as‐prepared copolymer (i.e., sol‐gel precursor) is then cohydrolyzed with various contents of titanium butoxide to afford chemical bondings to the forming titania networks to give a series of hybrid materials. Transparent organic–inorganic hybrid materials with different contents of titania are always achieved. Effects of the material composition on the thermal stability, optical properties, and morphology of neat copolymer and a series of hybrid materials, in the form of both coating and free‐standing film, are also studied by differential scanning calorimetry, thermogravimetric analysis, UV–Vis transmission spectra, refractometer, and atomic force microscopy, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 400–405, 2004     

Structure–property behavior of UV‐curable polyepoxy–acrylate hybrid materials prepared via sol–gel process

UV‐curable, hard, transparent organic/inorganic hybrid material with an improved mechanical property was prepared by the sol–gel process, based on a commonly used epoxy acrylate (EA) oligomeric resin. Systematic experiments were carried out to study the effect of the inorganic content, the acid content, and the content of a silane coupling agent on the property behavior of the hybrid materials. The structure of the hybrids were characterized by IR spectra and SEM observation. Results from thermogravimetric analysis (TGA) and mechanical measurement show that the properties of the hybrids differ with the changes of these variables. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1654–1659, 2003     

Water absorption characteristics of hybrid materials incorporating tetrabutyl titanate with acrylic polymer via sol–gel process

The sol–gel process was used to prepare organic/inorganic hybrids utilizing a terpolymer of n‐butyl methacrylate, methyl methacrylate, and methacrylic acid as an organic phase and titanium tetrabutoxide as a precursor of the inorganic phase. Such hybrid materials may be of interest as primers for corrosion protection of metal substrates. In the absence of electrochemical influence, which is usually provided by anticorrosive pigments in current protective coatings, the barrier mechanism becomes one of the basic elements for protecting metals against atmospheric corrosion. In that context, we report the water uptake characteristics of hybrid films with titania content up to 16.3 wt %. The slow hydrolysis of butoxy, acetate, and carboxylate ligands, which becomes more and more obvious with an increase in titanium oxide cluster content, is found to produce a chemically driven force for water uptake in hybrids. The 4.6 wt % TiO₂ hybrid results in the best balance of properties with a far lower diffusion coefficient and nearly the same amount of water absorbed at saturation compared to the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 92–102, 2005     

Morphology of Organic–Inorganic Hybrid Composites in Thin Films as Multichip Packaging Material

Silica–polyimide hybrid composites were prepared via a sol–gel process and thermal imidization. Two different types of soluble precursors, poly(amic acid) (PAA) and poly(amic diethyl ester) (ES), chemically convertible to poly(p-phenylene biphenyltetracarboximide), were used as organic polymer matrix component, and tetraethoxysilane (TEOS), convertible to silica, as the inorganic component. The structure of composites prepared as thin films was investigated by means of small-angle X-ray scattering, scanning electron microscopy and atomic force microscopy. Nanometre-scale composites were successfully obtained for ≤30wt% TEOS-loaded mixtures with ES and PAA. It was considered from the microstructural investigation that the composite films based on ES were not significantly affected by the inorganic particles generated, maintaining the structure of the homopolyimide, while those based on PAA did not preserve the structure due to the nanoparticles grown in situ during the sol–gel process. © 1997 SCI.     

A synergistic effect of nano‐Tio2 and graphite on the tribological performance of epoxy matrix composites

The influence of incorporated 300 nm TiO₂ (4 vol %), graphite (7 vol %), or combination of both fillers on the tribological performance of an epoxy resin was studied under various sliding load (10–40 N) and velocity conditions (0.2–3.0 m/s). Mechanical measurements indicated that the incorporation of TiO₂ significantly enhanced the flexural and impact strength of the neat epoxy and the graphite including epoxy. Tribological tests were conducted with a cylinder‐on‐flat testing rig. The incorporation of nano‐TiO₂ significantly improved the wear resistance of the neat epoxy under mild sliding conditions; however, this effect was markedly diminished under severe sliding conditions (high velocity and normal load). Nano‐TiO₂ reduced the coefficient of friction only under severe sliding conditions. Graphite showed a beneficial effect in reducing the wear rate and the coefficient of friction of the neat epoxy. Compared to the nano‐TiO₂‐filled epoxy, the graphite‐filled epoxy showed more stable wear performance with the variation of the sliding conditions, especially the normal load. A synergistic effect was found for the combination of nano‐TiO₂ and graphite, which led to the lowest wear rate and coefficient of friction under the whole investigated conditions. The synergistic effect was attributed to the effective transfer films formed on sliding pair surfaces and the reinforcing effect of the nanoparticles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2391–2400, 2006