Research into paints and organic coatings, functional layers and composite materials
at the Department of Paints and Organic Coatings
A number of research projects, scientific publications and cooperation with the industry at the Department of Paints and Organic Coatings are aimed at surface finishing of both metallic and non-metallic materials, active and passive surface protection and metallic substrate protection against corrosion. The paints industry provides the background and material basis for this research and related activities. The processing industry using the technology of painting and application of coating materials as well as additional numerous, diverse and rapidly developing surface finishing technologies in mechanical engineering and construction are also involved. This also concerns chemical industry producing starting materials for the formulation of paints – manufacture of paint binders, pigments for paints and plastics, and additives for paints and plastics. Also involved is the branch dealing with surface finishing and pretreatment, galvanic surface finishing, manufacture of phosphatizing products for conversion layers, degreasers, and many others. And last but not least, hot-dip galvanizing and hot-spray shops and the like. Worth mentioning are also industries manufacturing fillers for paints, plastics and composites.
Scientific activities at the Department of Paints and Organic Coatings are focussed on surface engineering. The scope of this research encompasses formation of inorganic-organic layers, nanomaterials, geopolymers and thin layers and paint coatings. In research into materials for surface finishing, special coatings are formulated, e.g. thermo-stable and anticorrosion coatings and paints with photocatalytic effects.
The mechanisms of reactions occurring at the organic coating–metal interface during corrosion processes are studied. Corrosion of metallic materials is a global problem and corrosion damages bring about large financial losses. If corrosion of a thermodynamically unstable metal, e.g. the conventional structural steel, is not stopped, the metal decomposes completely to corrosion products resembling the starting materials, which are thermodynamically more stable. Corrosion cannot be stopped completely, it can only be slowed down. Organic coatings as a measure to protect structural materials from corrosion are intended to eliminate or slow down electrochemical reactions occurring on the metal surface or at the organic coating–metal interface. The efforts to achieve protection of metallic materials against corrosion are aimed at finding such a material-environment system arrangement where its thermodynamic stability is enhanced and the rate of the corrosion reactions is reduced.
Investigation into the mechanisms of action of corrosion inhibitors in the protection of metallic materials and synthesis of environmentally friendly anticorrosion pigments represents a next area of scientific research at the Department. Materials showing promise for corrosion protection are synthesized. This includes, in particular, the development of corrosion inhibitors and environmentally friendly anticorrosion pigments. Nanoparticles and morphologically interesting pigment particles designed to provide complete and efficient interconnection within the forming polymeric coating are developed and synthesized. Research studying the processes of preparation of perovskite and ferrite type pigments for anticorrosion coatings is under way.
Core-shell particles and composite particles with active nanolayers preventing the occurrence of specific corrosion reactions are prepared. Making use of the synergistic effect of compounds reducing the rate of corrosion reactions – corrosion inhibitors – and the remaining components in the organic or inorganic protective coating appears to be a prospective solution. Application of electrically conductive polymers – polyaniline and polypyrrole – as corrosion process inhibitors is also a promising field of study. Other prospective materials, such as carbon nanotubes, are investigated as well.
Coatings containing conductive polymers are studied in collaboration with the Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, and their prospective applications are very interesting. Thermally and chemically stable coatings and coatings containing metallic particles or nanoparticles are developed and formulated. Prospective materials of natural origin, e.g. diatomaceous earths and morphologically interesting particles of silicate minerals are also tested.
An interesting form of corrosion, viz. filiform corrosion, and the options available for its inhibition are studied. Flash corrosion occurring when paint with a water-based dispersion binder is used is also investigated. Inhibitors against specific corrosion effects such as filiform corrosion and flash corrosion are being developed.
The feasibility of substituting a fraction of zinc metal with other materials in zinc-rich primers is currently studied by the Department. Zinc metal particles constitute an electrochemically active pigment which is frequently used in paints intended for "heavy" corrosion protection of metals. Reducing the zinc content is desirable for many reasons – environmental and well as technological. The mechanism of action of the zinc dust in primers with organic binders is based on electrochemical reactions and on the oxidation products' barrier effect. The goal of the research is to find a pigment (and its suitable concentration) that can substitute a fraction of zinc in the polymeric film while preserving or even enhancing the coating's anticorrosion efficiency, improving its physical parameters (adhesion and cohesion components in the paint), and reducing sedimentation of the heavy fraction in the liquid paint.
Geopolymer-based binders are used in some industrial applications. Modern coatings, building materials and cements contain geopolymeric binders with metakaolin and alkali silicate based activators. Geopolymeric coatings containing kaolin, metakaolin, and the like have been frequently discussed recently. Their advantages include chemical resistance and thermal stability. Scientists at the Department have been optimizing them by modification with fillers and pigments..
Study of catalysts for binders which dry by the oxypolymerization mechanism is also an important part of research at the Department. The goal is to identify new substances having a favourable effect on the setting of model films in combination with primary desiccants or new oxypolymerization reaction catalysts, test and find new types of potential agents accelerating the drying process and increasing surface hardness. Crosslinking reactions on polycondensation and polyaddition resins, binders obtained from renewables, and environmentally acceptable materials are studied. The effect of ferrocene derivatives on oxypolymerization drying of alkyd-type paint films is examined in detail, and spectroscopic methods are applied to investigate the mechanism of their action during the auto-oxidation reaction. Attention is also paid to other organometallic compounds that may potentially by usable in paints. For instance, some organometallic and complex compounds seem to show promise in this respect. So, pyrazolyl borate-manganese complexes may serve as secondary desiccants, and as much of two-thirds of the cobalt desiccant can be substituted. Interesting antioxidants of natural origin are also examined as potentially usable in paints. A substance with antioxidative properties, which in practical applications prevents too rapid skin formation, is a necessary additive in oxypolymerization binder systems. Attention in this respect is paid especially to propolis – a product of the honey bee (Apis melliflera).