Progress in Organic Coatings
Volume 33, Issue 2,
23 February 1998
, Pages 126-130
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Organic–inorganic hybrid coating systems based on polyesters and tetraethoxysilane (TEOS) are synthesized and evaluated to develop protective coatings with improved performance for prefinish construction steel and aluminium. The coatings have to combine flexibility, necessary for enduring deformation of the metal substrate after coating, and hardness for improved mechanical properties. Two systems have been studied: a polyester–TEOS system and a polyester–epoxide–TEOS system. The polyester–TEOS system contains polyester oligomers which are crosslinked with silica clusters, formed via the sol-gel process. The polyester–epoxide–TEOS system consists of an organic network of polyester and epoxide with silicon compounds, formed by the sol-gel process. Both systems form transparent hybrid organic–inorganic coatings. The influence of the inorganic compound on the König hardness of the coatings is determined. The polyester–TEOS system shows an increase in hardness with increasing silica content. It appeared difficult to incorporate in situ formed silica in the organically crosslinked polyester–epoxide–TEOS system.
Inorganic material can be synthesized via the sol-gel process in organic media at temperatures at which organic compounds are thermally stable . In this way it is possible to combine inorganic and organic components into one material: an organic–inorganic hybrid material. In the sol-gel process hydrolysis and condensation of metal alkoxides takes place. The most frequently used precursors are silicates. Gels are formed in the presence of water and an acid or base catalyst. The reactions of hydrolysis and condensation of alkoxy silane are shown in Fig. 1. Under acidic conditions the rate of hydrolysis is faster than the rate of condensation and a polysiloxane network is formed, while under basic conditions the rate of the condensation reaction is faster and dense silica particles are formed .
Schmidt prepared hybrid systems in the sol-gel process by adding organofunctional alkoxy silanes to TEOS (tetraethoxysilane) . Later, Schmidt and colleagues also incorporated organic molecules in these systems. In this way, both bulk and coating materials 4, 5were obtained. The glassy inorganic materials were made more flexible by the addition of organic compounds. The sol-gel technique is also used to improve the properties of organic materials by incorporation of metal alkoxides, for example the heat resistance of polyamides or the mechanical properties of elastomers 7, 8. Wilkes et al. used various polymers and oligomers for this type of hybrid systems to develop abrasion resistant coatings for polymeric substrates 9, 10, 11. In these systems the organic compounds were silane functionalized and combined with metal alkoxides. For the synthesis of harder organic-based coatings on glass substrates, Pascault's group also used the sol-gel process by adding organofunctional alkoxy silanes and metal alkoxides to organic oligomers .
Our aim is to prepare organic–inorganic hybrid coatings for coil coating applications, which integrate the flexibility of the organic phase and the hardness of the inorganic phase. In this paper the results obtained with the study of two systems are presented: a polyester–TEOS system and a polyester–epoxide–TEOS system. The polyester–TEOS system, based on polyester oligomers and TEOS, is used as a model system to study the chemical interaction between the organic and inorganic compounds and the influence of the chemical composition on the properties of the coatings . In the polyester–epoxide–TEOS system, an organically crosslinked coating system is combined with TEOS, to study the properties of the coatings for coil coating applications. Emphasis is laid on the influence of in situ formed silica on the hardness of the coatings.
A bifunctional hydroxyl-terminated polyester was synthesized from neopentylglycol, 1,4-cyclohexanedimethylol, esterdiol (HOCH2C(CH3)2CH2OC(O)C(CH3)2CH2OH), isophthalic acid and adipic acid by conventional methods . To obtain an acid-terminated polyester, the hydroxyl-terminated polyester was treated with succinic acid anhydride at 150°C for 1 h. After synthesis, the polyesters were characterized by endgroup titration and GPC. The characteristics of the polyesters are summarized in Table 1.
Interaction between the organic and inorganic phase
Transparent hybrid coatings in the polyester–TEOS system were only obtained from hydroxyl-terminated polyesters and TEOS, when the reaction was catalyzed by an acid (pTSA), in a moist atmosphere. No coatings were obtained from acid-terminated polyesters and TEOS. Neither were coatings were formed with a base catalyst. Under acidic conditions, TEOS hydrolyzes fast and then interaction between the polyester and hydrolyzed TEOS is possible via hydrogen bridging with the carbonyl groups or via
It was shown that transparent organic–inorganic hybrid coatings could be made from hydroxyl-terminated polyester and TEOS. The interaction between the organic and inorganic part occurs via the hydroxyl endgroups of the polyester and the hydroxyl groups of the silanols. Probably, a Si–O–C bond is formed by a condensation reaction. Increasing the TEOS content increases the silica content in the coating and causes an increased König hardness and Tg. It appeared difficult to incorporate silica in
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Historical Development of Hybrid Materials
2020, Encyclopedia of Renewable and Sustainable Materials: Volume 1-5
Hybrid material is widely known to possess excellent properties in terms of mechanical strength, thermosensitivity, chemical stability, optical and corrosion resistance, electrical and fire retardancy. In fact, thousands of new materials with unique property can be sourced to fulfill the requirement. Therefore, hybrid materials play a role in the future, especially in the engineering field, which includes the automotive, solar energy, solid-state lighting, civil engineering, aviation and aerospace industries. Now, hybrid material is used in the latest applications of dyes, coatings, catalysis, optics, optoelectronics, biomedical applications, and nanocomposites. So, hybrid material development is important in the modern technologies. This review article will explore the historical parts of hybrid material. Also, the article will highlight the hybrid material synthesis applied by the researcher and describe the hybrid material properties from the latest findings.
Water-based & eco-friendly epoxy-silane hybrid coating for enhanced corrosion protection & adhesion on galvanized steel
2016, Progress in Organic Coatings
Citation Excerpt :See AlsoThe impact of preferential orientations of organic cation on the spin textures of hybrid organic-inorganic perovskite CH3NH3PbX3 (X = Br, Cl)
In past few years, inorganic-organic hybrid films have been used to improve the performance of anti-corrosive coating on different metal substrates [1–3].
In this current study, epoxy-silane hybrid coatings were designed to investigate their anti-corrosion performance and adhesion on galvanized steel. Silanes with alkoxy group, epoxy group, amine group and thiol group were chosen to understand the role of functionalities in the performance of designed hybrid coatings. Moreover, the silanes were added at three different concentrations into epoxy polymer to asses the effect of concentration on anti-corrosion and adhesion properties of the coating films. From scanning electron microscopic (SEM) images, we observed a uniform coating without any agglomeration of coating particles over galvanized steel substrates. The corrosion performance of casted and cured films was evaluated by using potentiodynamic polarization and AC impedance spectroscopy method. The physical properties, such as, thermal behavior and thermo-mechanical behavior were studied using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) respectively. The adhesion strength between coating films and galvanized steel substrate was checked by ‘pull off’ adhesion test.
It was found that due to the grafting of sol-gel coatings onto organic polymer backbone, the adhesion property and anti-corrosive performance has improved remarkably as compared to non-grafted epoxy polymer. It was observed that amino silane showed superior performance compared to thiol silane. The poor performance of thiol silane grafted epoxy coating could be attributed to some chemical incompatibility of hydrophobic and non-polar sulfur silane moiety and hydrophilic and polar waterborne epoxy polymer backbone. Addition of silane by 1wt% and 3wt% into epoxy polymer backbone caused improvement in both anti corrosive property and adhesion strength but further increase of the silane concentration to 5wt% led to deterioration of protective property of the films. This drop in performance can be attributed to excessive consumption of epoxide groups in epoxy resin by amino and thiol functionalities present in silane.
Surface functionalized zinc oxide (ZnO) nanoparticle filled organic-inorganic hybrid materials with enhanced thermo-mechanical properties
2015, Progress in Organic Coatings
Citation Excerpt :
Organic–inorganic hybrid composites have recently attracted intense industrial and academic interests due to their remarkable and enhanced properties compared to unfilled resins. These materials exhibit the combined characteristics of organic polymer (e.g., flexibility, ductility, dielectric property) and inorganic materials (e.g., rigidity, high thermal stability, strength, hardness, high refractive index) [1–3]. Therefore, these materials could be widely used in the applications of protective coatings [4,5], high refractive index films , light-emitting diodes , solar cell  and optical waveguides materials [2,5].
The aim of this work is to use surface modified ZnO nanoparticles in combination with hyperbranched reactive polymer network to prepare moisture cure eco-friendly hybrid coatings and study their structure property relationship. The surface of the ZnO nanoparticles has been modified with silane coupling agent to get organo functional modified ZnO nanoparticles and were used for coatings formulation. The structure–properties of HBPUU (hyperbranched polyurethane urea)-modified nano ZnO hybrid materials were compared with HBPUU–nano-ZnO hybrid coatings. The viscoelastic, thermal and surface morphology of these coatings were characterized by Dynamic Mechanical and Thermal Analyzer (DMTA), Thermogravimetric Analyzer (TGA), Atomic Force Microscope (AFM), High Resolution Transmission Electron Microscopy (HR-TEM) and Contact Angle Instrument. TGA and DMTA data suggest higher thermal stability and glass transition temperature (Tg) for the coatings prepared using modified nano ZnO (5%) as compared to nano ZnO (5%) hybrids. The contact angle data suggest better hydrophobic character of the hybrid coatings prepared using modified ZnO. The AFM result suggests that the surface roughness value of modified nano ZnO hybrid coatings is less when compared to their corresponding nano ZnO based hybrid coatings.
Anti-corrosion hybrid coatings based on epoxy-silica nano-composites: Toward relationship between the morphology and EIS data
2014, Progress in Organic Coatings
Citation Excerpt :
Careful selection of a hybrid coating allows combining the desirable properties of organic part of system, i.e. toughness and elasticity with those of inorganic phase that is characteristic of good hardness, chemical resistance, and adhesion to the metal substrate via formation of covalent bonds [28–30]. Frings et al.  synthesized hybrid coatings based on polyesters and tetraethoxysilane (TEOS) to meet protective coatings exhibiting performance enhancement in prefinished steel and aluminum constructions. They have shown that increasing the TEOS content in the coatings causes an increase in the hardness and glass transition temperature (Tg).
This work reports on design and manufacture of organic–inorganic hybrid coatings based on diglycidyl ether of bisphenol A (DGEBA) epoxy resin pursuing hydrolyzation of tetraethoxysilane (TEOS) through a sol–gel process. The resulting hybrid materials were cured to be used as potential anticorrosive coatings. The assigned materials were modified molecules made of DGEBA and 3-aminopropyl triethoxylsilane (APTES), in which the molar ratio of epoxide group of DGEBA to NH of APTES varied in the order of 2:1, 4:1, 8:1 and 16:1. In the next stage, the APTES-modified DGEBA precursors were added to different amounts of pre-hydrolyzed TEOS, i.e. 7.5, 12.5 and 17.5wt%, as inorganic part of the resulting hybrid. The mixtures were subsequently cured at room temperature by a cycloaliphatic amine based curing agent to yield transparent epoxy–silica hybrid coatings. Microstructure assessment of the hybrid materials, before and after curing, was performed using FTIR and 29Si NMR spectroscopies. The morphology of the epoxy–silica hybrid coatings has also been studied by scanning electron microscopy (SEM). The anti-corrosive measurements on the resultant coatings were conducted based on electrochemical impedance spectroscopy (EIS). The mechanical properties evaluation such as micro-hardness measurements and pull-off adhesion tests of the cured samples were also carried out. The thermal properties of the cured hybrid coatings were evaluated using thermogravimetric analysis (TGA). The results showed that the concentration of APTES and pre-hydrolyzed TEOS play an important role in determining the morphology as well as the mechanical and thermal properties of coatings. The EIS results corresponding to these effects reaffirmed that the corrosion resistance of the hybrid coatings improved with increasing the inorganic phase content.
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