“Nanotechnology” refers to a wide range of scientific phenomena that focusses on the properties of developing materials by controlling individual atoms and molecules to create devices that are thousands of times smaller and with better electrical and chemical properties. Nanotechnology have thus paved a way in pharmaceutical and medical equipment, sporting goods, electronics, computers and imaging technology. Besides these, it also finds use as a pigment and mould inhibitor in latex paints and as coatings in paper as well as in the paint industry. All major paints and coating industries are known to have invested huge amounts on their research and development sector to formulate paints, that can serve to be compatible and suitable for today’s aggressive environment. For example, a good coating system having good chemical properties may be deterred by poor weathering properties or flexibility, or one with good flexibility may not have good thermal stability and mar resistance property. Hence, it would be a great achievement to develop a paint formulation satisfying many of such conditions. This aspect can be only fulfilled by the use of nanotechnology. For instance nanotechnology enables the production of electro conductive coatings that react with colour changes to mechanical stress.
In order to bring about this change in paints, nanofillers play a very important role in the paint composition. Incorporation of nanofillers in the polymeric coatings results in increased barrier properties, thermal stability, fire- resistance, transparency and colour purity as well as resistance to organic solvents. However, a common feature of most types of these polymers dispersions is their susceptibility to spoilage by micro organisms. Once growth occurs, a number of effects may be noticed including viscosity changes, production of gases, odours, colour changes and enzyme production with contaminant effects on products. The prevention of microbial contamination by incorporation of a preservative into the formulation requires a careful choice of biocide active agent, which is governed by the raw materials in the formulation. One such material used is nano ZnO that acts as a nanofiller and which helps prevent decay and contamination. ZnO nanoparticles in suspension form are used as anti-bacterial agents against E.coli disease causing bacterium. The ZnO nanoparticles actually damage the E.coli’s bacterial membrane walls. According to literature studies, it has been reported out that by the varying particle sizes and concentration the ZnO diamenter decreases and the bacteriostatic activity is improved. Moreover, nano ZnO is also used in wood preservation formula as it helps to provide the required longevity of performance. This is mainly because of the small size of the nanomaterial’s penetration into a porous surface rather than simple surface adhesion. The fine distribution of the ZnO particles ensures maximum substrate and film protection. The smaller and finer the ZnO particle distribution,, the higher the protection. Also impregnating wood with nano ZnO offers the advantage over nano-coatings of long term protection from photo degradation and biological deterioration, provided the treatment is leach resistant and bioactive. It also imparts resistance to water absorption and UV damage of wood.
Doped ZnOs are known to reside permanently in marine coating formulations, which can increase the lifetime of the antimicrobial activity indicating that cleaning and reapplication cycles can be extended. This is so because of the small size of the nanomaterials, the particles are held in the coating lattice and are not readily leached out of the coating by the marine environment while releasing ions to help provide longer- term anti- fouling characters. In addition, nano zinc oxide provides excellent corrosion resistance in saline water and excellent resistance to fouling of barnacles, shells and algae.
On the other hand, nano ZnO has the ability to offer UV protection while also being transparent in the UV spectrum. Optimal dosage of UV absorbers depends on coating thickness. Thin films require higher dosages, whereas for thicker films lower dosages are sufficient. Typically, low dosages of nano particles, 0.5-2%, provide significant and long term scratch, mar, wear corrosion and UV protection without adversely affecting gloss, clarity. According to previous literature reports, nano ZnO could reinforce the UV shielding ability of acrylic latex paint. Hence, nano ZnO are used to improve photostability as a component of UV coatings for nanocomposites or modelling UV permeability of nano ZnO filled coatings due to the fact that they are inorganic. They have advantages of being stable and non- migratory within an applied coating, thus allowing them to potentially offer better effectiveness and a longer service life.
Application of nano ZnO in the following coating industries are as follows:
i) Anti- bacterial coating
ii) Environmental protection coating
iii) Architectural coating
iv) Furniture coating
v) Industrial coating
vi) UV attenuated coatings