Organic–inorganic hybrid coatings for coil coating application based on polyesters and tetraethoxysilane (2023)

Chemical reactivity will have new traits in system combining organic and silicon compounds. In this paper, the kinetics of melt transesterification of dimethyl terephthalate (DMT) with a siloxane diol of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane (HP-TMDS) was fitted on the premise of the reaction mechanism obtained by quantum-chemistry calculation. This work reveals that the siloxane diol changes the reaction process and gives the classical transesterification its peculiarity, including more obvious advantage in kinetics for cyclic dimer and limited compatibility between reactant and catalyst. A solution is proposed to solve the problem resulting from the limited compatibility, which can be reference to any similar systems. The obvious advantage in kinetics for cyclic dimer brings a distinct feature in the product composition, which will provide more flexible and effective way to prepare silicon-containing polyesters.

Cross-linked thermoplastics represent an important class of materials for numerous applications such as heat-shrinkable tubing, rotational molded parts, and polyolefin foams. By cross-linking olefins, their mechanical performance can be significantly enhanced. This chapter covers the three main methods for the cross-linking of thermoplastics: radiation cross-linking, chemical cross-linking with organic peroxides, and cross-linking using silane-grafting agents. It also considers the major effects of the cross-linking procedure on the performance of the thermoplastic materials discussed.

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.

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 (T_g) 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.

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.

International Journal of Adhesion and Adhesives, Volume 95, 2019, Article 102388

The dry adhesion strength of polyester/melamine clear coats varying in their branching degrees were applied on galvanized steel panels and investigated by pull-off and T-bend testing. It was found that pull-off tensile adhesion is mainly dominated by the type of coating and less influenced by the pretreatment of the substrate. In contrast, the critical T-bend strain is mainly affected by the surface treatment of the galvanized layer with higher stiffness but lower ductility compared to the clear coat. Pull-off tensile strength at room temperature is correlating with the glass transition temperature T_g and a strong viscoelastic contribution is ascribed to the work of adhesion. Samples with adhesive as well as cohesive failure modes were further investigated by X-ray photoelectron spectroscopy (XPS) to determine the interfacial chemistry. Angle-resolved XPS data suggest that the nitrogen from the melamine crosslinker plays a decisive role for the adhesion of the coatings. Regarding the melamine distribution a micro- and a nanostructural effect has to be considered: while maximum melamine concentrations over coating depth are usually found in the bulk region of these clear coats, this work proposes that the remaining melamine at the interface segregates towards the metallic substrate.

Progress in Organic Coatings, Volume 154, 2021, Article 106198

Pre-painted metal sheet (PPM) is used in applications from domestic appliances to architectural cladding. The coating provides excellent aesthetics and corrosion protection, but must possess excellent formability to not fail due to the large strains applied during the folding and hemming processes used to produce components. Therefore it is important to understand how the coating formulation affects the free-film properties and formability of a coating system. Polyester coatings crosslinked with hexa(methoxymethyl)melamine (HMMM) with a T_g of ∼40 °C were used, pigmented with TiO₂. The glass transition temperature was increased by increasing the crosslinker content (from 5% to 30%), decreasing the adipic acid content (from 24% to 12%) and decreasing the molecular weight (from M_n = 3300 g/mol to M_n = 1500 g/mol). The chemical structure of the resin had little effect on the formability of the coatings when the test temperature was normalised with respect to T_g. The formability measured using the Erichsen cupping and T-bend tests is related to the tensile properties of the free-films. The damage induced by the T-bend is greater than that by the Erichsen cupping test due to the higher applied deformation rates in T-bend tests. Increasing the apparent yield and fracture stress increases the likelihood of damage at lower deformation levels, whilst increasing the strain to failure decreases the likelihood of damage in both the T-bend and Erichsen cupping tests. The strength of these correlations reduces with an increase in T-bend level as the magnitudes of the strains applied are reduced. This work takes a holistic approach to correlate structure and tensile properties with formability in both the Erichsen cupping test and T-bend test for the first time, enabling industry to improve coating performance significantly but cost-effectively.

Progress in Organic Coatings, Volume 150, 2021, Article 105963

Water-based coatings for pre-painted steel sheets are considered to be environmentally friendly alternatives to solvent-based coatings, such as those based on polyester and melamine. In the latter, surface melamine enrichment has been reported to confer good hardness and film formability. However, there is no information available on this phenomenon in water-based coatings, which is necessary to optimize their performance. Targeting this research gap, we compared the structures and properties of water- and solvent-based polyester/melamine coatings to decipher the mechanism of surface melamine enrichment in the former. Our studies suggest that in the absence of a catalyst, the marker resistance and surface nitrogen concentration were higher in water-based coatings than solvent-based coatings, even though their chemical compositions were similar. Analysis of the film structure showed that the surface melamine enrichment layer of the water-based film exhibited a higher melamine concentration than that of the solvent-based film. Dynamic mechanical analysis suggested that the crosslink density of the entire water-based paint film was higher than that of the solvent-based film. These results confirm that surface melamine enrichment and the crosslinking reaction are more promoted in water-based paints than in solvent-based products. Finally, we are of the opinion that our observations will help in improving the design and performance of water-based pre-painted steel sheets.

Infrared Physics & Technology, Volume 68, 2015, pp. 167-172

The fuze thermophotovoltaic (TPV) power supply converts the thermal radiation of fuze’s false cap into electric power directly and the generated power increases with the increasing of false cap’s temperature. Thus, in order to increase the temperature of the false cap, a two-section false cap consisting of two materials of different thermal conductivity is proposed. The results of numerical simulation indicate that compared with common false cap made of single material, the two-section false cap enjoys higher and more uniformly distributed temperature in the hemispherical nose’s inner surface, and thus its radiant power is greatly enhanced. Moreover, it is also verified by the experimental results that both the generation power and efficiency of fuze TPV power supply with two-section false cap are much higher than those of common false cap. Therefore, the two-section false cap contributes greatly to improving the performance of fuze TPV power supply and thus it can be applied to fuze power supply in the future.

Progress in Organic Coatings, Volume 135, 2019, pp. 613-621

A nano-structured hybrid compound was fabricated with excellent corrosion inhibitor encapsulating capacity and the ability of controlled delivery of benzotriazole (BTA) for simultaneous enhancement of the hydrophobic property and corrosion resistance of epoxy coatings. The Ce-metal organic frameworks (Ce-MOF) were synthesized and served as nanocontainers, tetraethyl orthosilicate (TEOS) was further added to form a film to wrap Ce-metal organic frameworks. The addition of benzotriazole into nanocontainers endowed coating system with excellent anti-corrosion performance. The novelty lies in that the tetraethyl orthosilicate membrane would break and produce pores to release benzotriazole uniformly under acid condition, which was a pH-controlled self-healing process through polymer coatings providing an effective release of corrosion inhibitor. The fabricated hybrid compounds were comprehensively characterized with Fourier Transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV-vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical Impedance Spectroscopy (EIS) was performed to characterize the corrosion behavior of various composite coatings. Results indicated that the 3 wt.%Ce-metal organic frameworks incorporated into the epoxy coatings showed the most excellent anti-corrosion property.

Procedia CIRP, Volume 99, 2021, pp. 266-271

The present work aims at studying the tensile behaviour of a hot-dip galvanized Z100 steel sheet, coated with a silicone-modified polyester resin. To this purpose, the pre-painted steel sheet was subjected to interrupted tensile tests at different strain levels in order to evaluate the elongation capability of both paint coating and steel sheet. The occurrence of superficial damages on paint coating was detected and the damage evolution before the sample fracture was analyzed. Furthermore, the thinning of each layer of the pre-painted sheet was also evaluated as a function of strain levels. Before the onset of necking, the degree of thinning on the different layers is almost uniform, whilst, once the necking was reached, a noticeable reduction in the thickness of both paint and steel sheet can be observed in the central zone of tensile sample.