Nanocomposite coatings based on alkyd resin with TiO2 and SiO2 nanoparticles

Design and development of new types of polymer based nanocomposites (NC) is rapidly emerging as a multidisciplinary research activity whose results could broaden the applications of polymers to the great benefit of many different industries: automotive, construction, aerospace, electrical and electronics, food packaging.1‒4 Polymers, resins and plastics containing additives such as clays and various nanostructures have recently become widely used as replacements for conventional materials of steel and other metal products, or their coatings, especially in the field of automotive industry. The application of the polymer NC coatings for the corrosion protection of steels was reviewed by Toshiaki Ohtsuka5 he reported various systems mainly based on conductive polymer matrix. The incorporation of layered silicates into polymer matrix was a research focus for many years, since the results of the Toyota research team showed that the incorporation of 2 vol% of exfoliated clay into Naylon-6 contributes to about 90oC increase in glass transition temperature and double Young’s modulus.4 Traditionally, alkyd resins as oil-modified polyesters, have been placed amongst the most widely used resins in exterior solvent-based inexpensive coating applications because of their high gloss and durability. Alkyd-based nanocomposite coatings were reported to exhibit better properties compared to the traditional ones.2 It was shown that water vapour permeability of nanocomposite coatings remarkably decreased with respect to neat coating. For example, a decrease of water vapour permeability by a factor of 15 has been measured.1 Inorganic–organic composites based on organo-alkoxysilanes and other alkoxides have demonstrated their usefulness even for hard coatings on eye-glass lenses.6 It has been shown that the addition of nanoparticles, especially in combination with epoxy silanes, which act as an inorganic as well as an organic crosslinking agent, leads to a substantial increase of the abrasion resistance of such systems without losing any transparency. Therefore, due to the incorporation of nanoparticles into the certain polymer matrix, high abrasion resistance can be obtained.1,5 Avella et al.7 have shown that the presence of only 2% nanoparticles strongly improves the abrasion resistance, as well as the wear of Poly(Methyl methacrylate) (PMMA). 6 The nanocomposites showed an average weight loss about half (2,5% against 5% of removal material) with respect to that of neat polymer.