What is nanotechnology?

The word nano is derived from the Greek word (Dwarf) which means very small particles of matter with the size of one thousandth of a micron or one billionth of a meter. Nanotechnology is the technology of using particles on the nanoscale and organizing them in a suitable way in order to produce new materials with multiple characteristics and improved properties that are not possible with conventional methods

 

Application in coating industryThe use of nanoparticles in the coating industry has been used for a long time. Latex emulsions with particle sizes between 100 and 500 nm are used in the composition of construction paints. Rutile (Rutile TiO2), which is one of the inorganic polymorphs of TiO2, is nano-silica as a thixotropic agent, among the many examples of the application of nano materials in coatings.

Micron-sized particles are used with pigments and macro (coarse) fillers by classical mixing methods. In these types of mixtures, heterogeneity on the macro scale is completely present. Since there is a large phase boundary (due to the presence of polymer and mineral phases) many properties such as optical, mechanical and proper permeability cannot be achieved. But if nanoparticles between 10 and 100 nm in size enter the coating composition, it will lead to the formation of mixtures on a molecular scale, and thus there will be no phase boundaries, and this will lead to the formation of homogeneous compounds with improved properties.

The set of properties of the coating that can be fundamentally changed by using nano particles are: Physical properties such as densityMechanical properties such as wear, bending, impactOptical properties and refractive indexAbility to increase resistance to UV raysImproving the flammability delay propertyImproving anti-corrosion properties

Currently, nanoparticles are usually used in the form of powder at the commercial level, and the ones that have more industrial applications than other particles are: nano silica, nano clay, nano rutile (nano titanium oxide), nano zinc oxide, nano iron oxide, nano Carbon atoms and carbon nanotubes. In some cases, these nanoparticles are produced during the reaction and are then mixed with the polymer system through appropriate methods. From a technical point of view, the introduction of nanoparticles in the cap can be done in one of the following ways: Chemical mixing (for example, sol-gel method)Controlled physical mixing like other fillers and extendersModification with suitable organic compoundsCreate a chemical bond

Types of modified coatings using nanotechnology:

Anti-wear coatings:Anti-wear coatings made of epoxy-silica nanocomposites for steel can be made by combining Alkoxysilanes (a group of silicone compounds that includes alcohol and silica) and their derivatives with epoxy resins through the sol-gel process. prepared Low-viscosity liquid epoxy resins grafted to nano-silica by a suitable method lead to a new class of epoxy coatings that have good scratch and abrasion resistance.

Long-lasting exterior coatings: These coatings are based on silicon acrylic latex modified with nano silica. Alkoxysilanes introduce silicone polymers into acrylic emulsion latex through hydrolysis and polymerization. Due to the amount of nano-silica, durable acrylic latexes show a significant improvement against corrosion, plastering, preservation of color and glossiness.

Transparent layer with very high scratch resistance for cars: How the car body resists acid washing and scratch test is very important because it has a significant effect on the appearance of the car and its resistance to washing brushes. The latest product currently belongs to PPG company, which is based on silicate nanoparticles, it has led to the production of a new generation of transparent layers for cars, which has good transparency and excellent resistance to scratching, UV and acid washing

Wood coatings: The most common problem in wood coating is yellowing because lignum (Lignum is a complex polymer that is the most common compound in the structure of woody and non-woody plants after cellulose) in wood is oxidized by light and the transparency of the layer The final removes the wood. The most common solution to solve this problem is the use of organic UV absorbers and HALS (light stabilizers of hindering amines). These materials are toxic and lose their effectiveness during the working life of the wood. Nanoparticles (5 to 10% titanium dioxide nanoparticles Tio2 or zinc oxide nanoparticles) can completely solve this problem. They create a strong and suitable shield against UVA and UVB rays.Their non-toxicity and very long life is due to the fact that these are minerals. Nano TiO2, nano ZnO and nano iron oxide all act as effective filters for UV rays and prevent wood degradation and yellowing problems.

 

Anti-wear coatings:Nano particles of titanium dioxide are used in the protective coatings of valves for the oil, gas and petrochemical industries. Compared to normal coatings, their resistance to wear caused by dry sand has increased 25 times and resistance to mechanical erosion has increased 3 times

Anti-pollution coatings:Paints based on titanium dioxide nanoparticles can absorb harmful air pollutants such as CO, NOx and turn them into safe gases through oxidation with peroxy and hydroxy radicals formed on the surface.

Self-cleaning coatings: Coatings with biological properties and health applicationsNano particles of titanium dioxide can oxidize sticky organic pollutants on the surface and turn them into non-sticky materials. At the same time, these active radicals can have antimicrobial and biological effects and make surfaces free of microbes. The two properties of ease of cleaning and antimicrobial properties of titanium dioxide nanoparticles provide its use in special applications of sanitary and hospital coatings. These types of coatings are usually water based. and have self-cleaning properties that are transferred from the depth of the color film to the surface of the color film.

Self-cleaning coatings with anti-corrosion effect

The performance of these coatings is through reducing surface energy and by creating a polished surface, they cause self-cleaning of the surface. These coatings are usually solvent based. Researchers around the world have tried to produce surfaces that have very low surface energy and can be controlled at the micro and nano scale. It was in this way that superhydrophobic surfaces were created. According to research, it is almost impossible to create a contact angle of more than 120 degrees on a flat surface, just relying on the hydrophobic chemical structure of that surface and without any structure in nano or micro dimensions.

Therefore, to create super-hydrophobic surfaces, two conditions of surface roughness and hydrophobicity (low surface energy) must exist. The impermeability of the surface against water reduces the destruction and corrosion of the coated product.

It is clear that nanotechnology has changed the process of development and research in the field of coatings and offers new solutions to improve the performance of coatings, but the high price has blocked the way for large-scale development, although the designers of research and development In the field of coatings, they have always focused a part of their thinking on this sector and it is predicted that a huge wave of new design methods and new coatings with unique properties will cover the world of colors and coatings.

 Reference: Surface Coating International, Part A, Journal of Paint and Resin Manufacturers Association, No. 30Editing and adaptation of the report: Setare Asgari