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     

Synthesis and characterization of novel polyimide/SiO2 nanocomposite materials containing phenylphosphine oxide via sol‐gel technique

In this article, a series of novel polyimide/silica (PI/SiO₂) nanocomposite coating materials were prepared from tetraethoxysilane (TEOS), γ‐glycidyloxypropyltrimethoxysilane (GOTMS), and polyamic acid (PAA) via sol‐gel technique. PAA was prepared by the reaction of 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) and bis (3‐aminophenyl) phenyphosphine oxide (BAPPO) in N‐methyl‐2‐ pyrrolidone (NMP). BAPPO was synthesized hydrogenation of bis (3‐nitrophenyl) phenyphosphine oxide (BNPPO) in the presence of Pd/C. The silica content in the hybrid coating materials was varied from 0 to 20 wt %. The molecular structures of the composite materials were analyzed by means of FT‐IR and ²⁹Si‐NMR spectroscopy techniques. The physical and mechanical properties of the nanocomposites were evaluated by various techniques such as, hardness, contact angle, and optical transmission and tensile tests. These measurements revealed that all the properties of the nanocomposite coatings were improved noticeable, by the addition of sol‐gel precursor into the coating formulation. Thermogravimetric analysis showed that the incorporation of sol‐gel precursor into the polyimide matrix leads to an enhancement in the thermal stability and also flame resistance properties of the coating material. The surface morphology of the hybrid coating was characterized by scanning electron microscopy (SEM). SEM studies indicated that nanometer‐scaled inorganic particles were homogenously dispersed throughout the polyimide matrix © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Barrier properties of organic–inorganic hybrid coatings based on polyvinyl alcohol with improved water resistance

A comprehensive study of the gas barrier properties of hybrid organic–inorganic coatings formed by polyvinyl alcohol (PVOH) and Si‐SiO₂, obtained via sol–gel technique, was carried out. It has been shown that the oxygen, nitrogen and carbon dioxide transfer rates of barrier polymers such as poly(ethylene terephthalate) and oriented polypropylene can be further reduced, by up to two orders of magnitude, with a thin coating (1–2 μm) of PVOH/Si‐SiO₂. More notably, it has been observed that the material maintains this feature even after a prolonged contact with water, which is a strong solvent for PVOH. Direct moisture sorption measurements show that silica lowers the water uptake of PVOH and inhibits sorption‐induced swelling and plasticization of the polymer. Correlations between the gas transport properties of the hybrid coatings and factors such as the silica content, the type of polymeric substrate, the nature of penetrant and the temperature have been found, providing guidelines for the selection and design of multilayer materials for packaging applications. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

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     

Antireflective coatings using organically modified silica and polyimide via solution casting method

Antireflective (AR) coatings were prepared using a polyimide and two types of organically modified silica colloids via a solution casting method. The optically transparent polyimide was prepared from 2,2′‐Bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 4,4′‐oxydianiline (ODA). The silica colloids were driven to the coating‐air interface by either the fluorinated alkyl group or PDMS (Polydimethylsiloxane) segment tethered onto the silica colloids. The amount of fluorinated alkyl groups and the molecular weight of the siloxane grafted on the silica colloid were varied. The PDMS‐silica and fluorosilica colloids were characterized by TEM (Transmission Electron Microscopy), DLS (Dynamic Light Scattering), FTIR (Fourier Transform Infrared Spectroscopy), solid‐state ¹³C NMR (Nuclear Magnetic Resonance) and solid‐state ²⁹Si NMR. The AR coatings were characterized by UV–vis (Ultraviolet–Visible Spectroscopy) transmittance spectra, AFM (Atomic Force Microscope), and SEM (Scanning Electron Microscope). The effects of modified silica loading and type of solvent on AR properties were studied. An enhancement in AR activity was observed for 1 wt% PDMS‐modified (low molecular weight) silica coatings and 3 wt.% fluorosilica‐10 in dimethylacetamide (DMAc). In comparison with cyclopentanone (CPT), DMAc favors migration of silica particles toward coating‐air interface giving higher transmittance. The migration of particles to the surface and consequently increased surface roughness was observed by SEM. POLYM. ENG. SCI., 53:2228–2241, 2013. © 2013 Society of Plastics Engineers     

Highly crosslinked nanocomposites of aromatic dicyanates/SiO2 via the sol–gel method

Highly crosslinked nanocomposites of bisphenol A dicyanate (BADCy) containing silica clusters were successfully prepared via the sol–gel process. The silica clusters were generated from various metal alkoxide precursors, including methyltrimethoxysilane (TMOS), 3‐glycidoxypropyltrimethoxysilane (GPOS), and 2‐(3,4‐epoxycyclohexyl) ethyltrimethoxysilane (ECOS). The metal alkoxide precursors GPOS and ECOS were, in turn, used as coupling agents. Three kinds of systems involving BADCy/TMOS, BADCy/coupling agent, and BADCy/TMOS/coupling agent were individually prepared and thoroughly investigated using various methods. Each kind of system was of a particular characterization and morphology and had distinct physical and dielectric properties. Isolated silica clusters on a nanoscale were homogenously distributed in the highly crosslinked BADCy/TMOS hybrid system. The characterization of BADCy/TMOS nanocomposites showed improved physical properties, when compared with the neat BADCy network. The particle sizes can be controlled by adding different amounts of TMOS and are slightly increased (in the range of 50–105 nm) with increasing TMOS content. On the other hand, in the highly crosslinked BADCy/coupling agent hybrid system, the silica clusters were tethered to the BADCy matrix by the coupling agent. An oxazoline linkage was detected during the reaction of cyanate groups in BADCy with the epoxide groups in the coupling agent. These nanocomposites exhibited weakened mechanical properties but are of a smaller and more homogenous particle size in the range of 30–50 nm, irrespective of the silica content. Finally, the BADCy/TMOS/coupling agent system was successfully designed to combine the advantages of the two systems mentioned above. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1356–1366, 2007     

有机硅烷共缩合制备抗紫外超疏水减反射涂层

具有超疏水自洁功能的减反射涂层对太阳能光热组件在室外长期使用上有重要的意义,可以减少减反射涂层的清洗成本,延长减反射涂层的使用寿命。利用含有甲基和乙基等疏水基团的有机硅氧烷制备具有一定孔隙率的涂层,有望实现减反射和超疏水双重性能。本研究采用四甲氧基硅烷（TMOS）和甲基三乙氧基硅烷（MTES）共缩合,并利用甲氧基三甲基硅烷（MMS）进行羟基封端,制备了可以稳定两个月以上的均一溶胶。通过控制MTES和TMOS的水解工艺条件,采用浸渍提拉法制备了在400～800nm可见光波段平均透光率为97.06%、最高透光率为98.27%、水接触角为165°的超疏水减反射涂层,提出了MTES/TMOS/MMS溶胶的共缩合反应机理。涂层经过紫外耐久测试1080h后,涂层仍具有良好的减反射性能、疏水性和抗刻划强度,表现出良好的紫外耐久性。     

Functionalized Hybrid Coatings on ABS Surfaces by PLD and Dip Coatings

It is important to give water-repellent and antibacterial properties to the acrylonitrile butadiene styrene (ABS) surfaces of the hearing aids. In this study, the sol–gel Si and sol–gel Ti solutions were prepared from the reactions of silicon ethoxide, titanium butoxide and methacrylic acid. The catalyst and Dynasylan F8815 were added to the sol–gel solutions to give hydrophobic properties onto the ABS surfaces. Additionally, silver nanoparticles were synthesized by nanosecond laser and added to the coating solutions to give extra antibacterial properties. The surfaces of the ABS targets were coated using the sol–gel dip coating and pulsed laser deposition techniques. The coatings with good adhesion between film and substrate and good water-repellent properties were achieved. The average contact angles for the coated ABS surfaces were measured in the range between 120 and 125 degrees. The obtained sol–gel materials and produced thin films onto the ABS surfaces were also analyzed in terms of the antibacterial properties. The highly antibacterial properties were observed in the sol–gel solutions and the thin films.     

Preparation and characterization of epoxy resin modified with alkoxysilane‐ functionalized poly(urethane‐imide) by the sol–gel process

The sol–gel process has been frequently employed for preparation of high performance silica/polymer composites. In this paper, novel sol–gel precursor triethoxysilane‐terminated poly(urethane‐imide) (PUI‐Si), combining the advantages of polyurethane (PU) and polyimide, was synthesized and characterized. Then PUI‐Si was incorporated into the epoxy resin matrix to prepare a series of EP/PUI‐Si organic‐inorganic hybrids through an in situ sol–gel process and crosslinking reactions. The thermal stability of EP/PUI‐Si hybrids was evaluated by thermogravimetric analysis and the results show that the PUI‐Si could significantly improve the thermal properties of epoxy resin. The initial decomposition temperature of composites with 50 wt% PUI‐Si reached 347.1 °C, 157.3 °C higher than that of neat epoxy resin. Furthermore, the tensile strength and breaking elongation can also be clearly improved by adding a suitable amount of PUI‐Si. Similarly, the water contact angle increased to 97.4° with 70 wt% PUI‐Si, showing a hydrophobic surface. The morphology was investigated by transmission electron microscopy and the results reveal that the silica particles are smaller than 20 nm and have a strong interaction with the epoxy resin matrix, resulting in the above‐mentioned high performance properties. Copyright © 2011 Society of Chemical Industry     

Effect of addition of surface modified nanosilica into silica–zirconia hybrid sol–gel matrix

An organic–inorganic hybrid sol (MZ) comprising a methacrylate functionalized silane matrix (M) and zirconium-n-propoxide (Z) was prepared using sol–gel technique. Two methodologies were adopted to modify the hybrid sol for generating nanocomposite coatings viz., (a) addition of acrylic surface modified silica nanoparticles (N) of diameter ～20 nm to the sol to enhance their compatibility with the hybrid sol–gel matrix and (b) in-situ formation of a three dimensional silica network by addition of tetraethoxy silane (T) to the sol MZ. In the first methodology, the sols were prepared with six different weight ratios of the nanoparticles to the sol, i.e. 0, 0.01, 0.05, 0.1, 0.25 and 1 which were labelled as MZ+Nx where x=0, 1, 2, 3, 4 and 5 respectively. The prepared sols were dip coated on 100 mm×100 mm polycarbonate substrates followed by thermal curing at 130 °C. The coatings were characterized for their mechanical properties like pencil scratch hardness, scratch resistance using scratch tester, nanoindentation hardness, and abrasion resistance as well as visible light transmittance. FT-IR studies were also carried out on heat-treated gels derived from the sols. A maximum pencil scratch hardness of 3H was obtained for the MZ+T coatings and these coatings withstood a critical load of 4.3±0.7 N before failure during scratch test. The maximum nanoindentation hardness of 3.8±0.01 GPa was obtained for the MZ+N5 coatings. The abrasion resistance of MZ+T coatings was higher when compared to MZ+N0 and MZ+N5 coatings. The scratch and nanoindentation hardness were seen to be better for an in-situ formed –Si–O–Si– network in the hybrid sol when compared to those obtained from coatings generated by external addition of acrylic surface modified silica nanoparticles. The difference in properties was attributed to the level of interaction between the nanoparticles and hybrid sol–gel matrix.     

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.     

Effect of silanes on the morphology,hydrophobicity, and dynamical mechanical properties of polyimide/silica hybrid membranes

Polyimide (PI)/silica hybrid membranes with high contact angles were prepared through the in situ sol–gel process. The precursor, poly(amic acid) with controlled block chain length, was synthesized using 4,4′‐diaminodiphenyl ether (ODA), 3,3′,4,4′‐benzophenone‐tetracarboxylic dianhydride (BTDA) and 3‐aminopropyl‐trimethoxysilane (APrTMOS) or 3‐aminopropyldimethylethoxysilane (APDiMOS). And then, phenyltrimethoxysilane (PTS) or tetramethoxysilane (TMOS) or methyltrimethoxysilane (MTrMOS) was respectively, added to the above polyamic acid and mixed thoroughly. Following curing reaction, the PI/silica hybrid membranes with different cross‐linkages, silica content, and hydrophobic properties were prepared. The effect on the formation of PI imide ring during imidization reaction is increased as the increase of silanes content and characterized by frequency shiftment and absorbance ratio of Fourier transform infrared (FTIR) measurements. All the hybrid membranes show high transparency though with high silica contents. The storage modulus, tan δ, and damping intensity by DMA measurements are all correlated with silane content or block chain length. And all these membranes with silane content possess high contact angle as compared to pure PI without any silanes added and the contact angles increase with increasing the silane content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of baking treatment and materials composition on the properties of bulky PMMA–silica hybrid sol–gel materials with low volume shrinkage

A series of bulky PMMA–silica hybrid sol–gel materials had been successfully prepared through the conventional HCl‐catalyzed sol–gel approach with 2‐hydroxyethyl methyl methacrylate (HEMA) as coupling agent under pumping pretreatment (i.e., exhaustive vacuum evacuation). In this work, the hydroxyl groups of HEMA monomers were first cohydrolyzed with various contents of tetraethyl orthosilicate (TEOS) to afford chemical bonding for the forming silica networks by removal of solvent and byproduct of sol–gel reactions through pumping pretreatment before gelation reactions. Subsequently, the resultant viscous solution was then copolymerized with methyl methacrylate (MMA) monomers at specific feeding ratios by using benzoyl peroxide (BPO) as free‐radical initiator. Eventually, transparent bulky organic–inorganic hybrid sol–gel materials loaded with different silica content were always achieved. The obtained bulky hybrid sol–gel materials were found to be transparent, crack‐free, and of relatively low volume shrinkages even in high silica content. The as‐prepared bulky hybrid sol–gel materials were then characterized through silicon element mapping studies of energy‐dispersive X‐ray (EDX) and transmission electron microscopy (TEM). Effect of heating process at 150°C for 5 h after polymerization and material composition on the thermal properties, mechanical strength, and optical clarity of a series of bulky PMMA–silica hybrid sol–gel materials was investigated and compared by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), hardness test, dynamic mechanical analysis (DMA), and UV–vis transmission spectroscopy, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1151–1159, 2006     

Preparation and performance on polycarbonate of B/F/Si‐containing hybrid coatings

A series of UV‐curable B/F/Si‐containing hybrid coatings was prepared by the anhydrous sol‐gel technique. The chemical structure of the coatings was characterized by FTIR, RTIR, and ¹HNMR techniques. The UV‐curable coatings were applied to polycarbonate substrates. The physical and mechanical properties of the UV‐cured coatings, such as pendulum hardness, pencil hardness, contact angle, gel content, MEK rubbing test values, tensile strength, abrasion resistance, and gloss, were examined. Thermal gravimetric analysis (TGA) was done. The relative flammability of the hybrid coatings was tested by the limiting oxygen index (LOI) method. Results of all analyses conducted on the free films and coatings are discussed. J. VINYL ADDIT. TECHNOL., 19:39–46, 2013. © 2013 Society of Plastics Engineers     

Abrasion resistance of ceramic thin films of ZrO2/SiO2 on stretched grade polymethyl methacrylate substrates

Abrasion resistance of stretched grade polymethyl methacrylate (PMMA) was increased by using the sol–gel method to have it coated with a ZrO₂/SiO₂ thin film. Different molar ratios of Zr(OPr)₄/Si(OPr)₄ sols were prepared as precursors with propanol. These sols were used for dip-coating the stretched PMMA surfaces to establish very smooth thin films of amorphous Zr–O–Si. Fourier Transform Infrared spectroscopy (FT-IR) was employed to study vibrations of Zr–O–Si bonds within the thin film. The phase analysis was undertaken via X-ray Diffraction (XRD) method. The morphology and thickness of coatings on PMMA were investigated by means of Scanning Electron Microscopy (SEM). The results showed that coating had an amorphous structure with its thickness within the range of 80–100 nm. The water contact angle of PMMA substrates altered from 73° before coating to less than 64° after coating. Once coated, the PMMA substrate had its transparency characteristic (within the UV–vis region) increased. Furthermore, the influences of thermal treatment temperature and molar ratio of precursors (Zr(OPr)₄/Si(OPr)₄) on abrasion resistance of the coatings were studied.     

Organic–inorganic hybrid materials. II. Chain mobility and stability of polysiloxaneimide–silica hybrids

Polysiloxaneimide–silica hybrid materials (PSI‐SiO₂) were obtained using the sol–gel technique by polycondensation of tetramethoxysilane (TMOS) in a polyamic acid solution. IR, ²⁹Si‐ and ¹³C‐NMR spectroscopy, and thermogravimetric analysis were used to study hybrids containing various proportions of TMOS and hydrolysis ratios. The morphology, dynamics, and thermal stability of the hybrids were investigated. The chain mobility of the hybrids was investigated by spin–spin relaxation time (T₂) measurements. The apparent activation energy (E_a) for degradation of the hybrids in air was studied by the van Krevelen method. The T₂ value was independent of the silica content whereas that of the E_a decreased as silica content increased. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 965–973, 2001     

Preparation of HMDS-modified silica/polyacrylate hydrophobic hard coatings on PMMA substrates

Colloidal silica nanoparticles synthesized from tetraethoxysiliane via a sol–gel process were surface modified by 3-(trimethoxysilyl)propyl methacrylate (MSMA) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS). MSMA acted both as a C=C provider and a coupling agent, whereas HMDS was used to prevent particle aggregation and engender hydrophobicity. The modified silica particles (HMSiO₂) were UV-cured together with the crosslinking agent, dipentaerythritol hexa-acrylate (DPHA) to form coatings on poly(methyl methacrylate) (PMMA) substrates. Dynamic light scattering of the synthesized sols indicated that the average size of HMSiO₂ was ca. 10 nm, consistent with that obtained from TEM imaging. FTIR spectroscopic analyses demonstrated chemical attachment of HMDS to the silica particles. The cured coatings were characterized in terms of water contact angle, light transmittance, hardness, abrasion resistance, and surface morphology. It was found that hydrophobicity of the coatings increased while light transmittance and hardness decreased with increasing HMDS content. DPHA played the role of providing mechanical strength and adherence; however, the coatings became lightly hazy when the weight ratio of DPHA/silica fell in the range 0.3–0.7. In the optimal case, a hard coating (4H) with water contact angle of 108° and transmittance of ~100% (vs PMMA) had been obtained at the DPHA content of 10 wt%.     

Corrosion protection of aluminum alloy substrate with nano-silica reinforced organic–inorganic hybrid coatings

Organic–inorganic hybrid (OIH) thin films derived from the sol–gel process have emerged as sustainable metal pretreatment alternatives to toxic heavy metal-based systems. In recent years, such OIH systems based on Si, Zr, and Ti have been successfully developed and commercialized for pretreatment of aluminum alloys, galvanized steel, cold-rolled steel, and many other metals and alloys, for improving adhesion and corrosion resistance performance. A variety of approaches are being used to further enhance performance of such OIH systems to match or surpass that obtained from chromate-based systems. In the present study, a novel bis-silane compound has been synthesized and used as a primary sol–gel precursor for OIH coatings. In order to further improve their mechanical and corrosion resistance performance, colloidal nanoparticles have been incorporated. The microstructure of the deposited films as a function of their composition and formation of Si–O–Si structural network has been studied by Confocal Raman spectroscopic technique. The chemical structure of the OIH films has been characterized by FTIR analysis. Electrochemical impedance spectroscopy, DC polarization measurements, and accelerated neutral salt-fog test (ASTM B117) have been used to evaluate corrosion resistance performance of coatings on industrial aluminum alloy AA 3003 H14. Nano-indentation tests of these OIH films have been performed to study the effect of colloidal nanoparticles on coating micro/nano structure and their mechanical properties. The study reveals that colloidal nanoparticles improve the corrosion resistance of OIH coatings by formation of a protective barrier to diffusion of corrosive species to the metal surface. The optimum content of colloidal nanoparticles that can provide best corrosion protection has been determined. Electrochemical study provides useful insight into the significance of interaction between the sol–gel hybrid and silica particles in the corrosion protection mechanism.     

Heat‐resistant hydrophobic–oleophobic coatings

Thermally and chemically durable hydrophobic oleophobic coatings, containing different ceramic particles such as SiO₂, SiC, Al₂O₃, which can be alternative instead of Teflon, have been developed and applied on the aluminum substrates by spin‐coating method. Polyimides, which are high‐thermal resistant heteroaromatic polymers, were synthesized, and fluor oligomers were added to these polymers to obtain hydrophobic–oleophobic properties. After coating, Al surface was subjected to Taber‐abrasion, adhesion, corrosion, and thermal tests. The effects of the particle size of ceramic powders, organic matrix, and heat on the coating material were investigated. Coating material was characterized by FTIR spectrophotometer. Surface properties and thermal resistance of the coating materials were investigated by SEM and TGA analyses. After thermal curing, contact angles of these coatings with H₂O and n‐hexadecane were measured. It was observed that coatings like ceramic particles are more resistant against scratch and abrasion than the other coatings. Also, they are harder than coatings, which do not include ceramic particles. It was seen that coatings, containing Fluorolink D10H, have high‐contact angles with water and n‐hexadecane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2386–2392, 2006