Nanogate AG works on surfaces for building and interior since years. Nanotechnology is one of our most important tools and offers a wide range of possibilities to solve problems. Our technology can be used to enhance and to protect well known materials and products and to open new and alternative production processes.
The Södra Länken tunnel system was treated with one of our nanoscaled impregnations upon the commission of the city of Stockholm. The system drastically reduces the amount of dirt and grime which clings to the surface, thus reducing expensive cleaning phases with aggressive materials. This saves considerable costs while the system moreover makes a sustained contribution to the environment and traffic safety. On the basis of this system a range of ready-to-use products and additives was developed. These materials offer a lot of other possibilities to enhance surfaces, to reduce soiling and maintenance and to conserve value.

By combining latest photocatalyst, hydrophobic and nanotechnology achievements, NANOBIZ has developed powerful and extremely effective self-cleaning, and easy-to-clean solutions for civil engineering. The applications actively decompose bacteria, biological and chemical pollutants as well as toxins, bad odors, mold and other fungi, once they come in contact with any surface that has been treated with the coatings.
The powerful self-cleaning effect is based on a thin film of titanium dioxide, which is a photo-catalyst material applied on the treated surface. The thin film chemically bonds to the surface and starts to absorb ultraviolet ray in the sunlight or artificial light to react with water vapor to form a strong oxidizing agent known as the hydroxyl radical. When the photo-catalyst captures ultraviolet light, it forms activated oxygen from water or oxygen in the air. Utilizing the clean energy of light and strong oxidizing strength of the hydroxyl radical, any toxins floating in the air are destroyed once they come in contact with the treated surface such as building elevations, facades, windows, walls, floors and many others.
On the other hand, easy-to-clean solutions are coatings created to permanently protect various kinds of surfaces used in constructions. The coatings give the protected surfaces hydrophobic and stay-clean properties, which make them functional and keep the surface’s original looks

Deposition of air pollutants and biological growth on cementitious materials are common phenomena, which by staining or colour changes decrease aesthetic quality. Different strategies can be used for prevention of fouling, such as application of water repellents and/or biocides. A modular setup was designed which allows the simultaneous evaluation of different product formulations applied on concrete or stone. Algal fouling can be evaluated by means of colorimetric and image analysis. For white concrete, application of water repellents or biocides allowed to eliminate algal fouling. For autoclaved aerated concrete (AAC), which has a high bioreceptivity, the best performance was obtained with a combination of a water repellent and a biocide.

Self-cleaning properties can also be obtained by application of coatings with photocatalytic TiO2 particles. When exposed to UV radiation, titanium dioxide will form highly reactive species like the hydroxyl radical and the superoxide radical-anion, showing strong ability to degrade micro-organisms and pollutants. It was also found that TiO2 films developed a superhydrophilic behaviour under UV light exposure. In our group, the application of TiO2 on cementitious materials using different coating techniques, is studied.

The number of commercial products that utilise a photocatalytic coating continues to increase and includes: self-cleaning glass, tiles and paint. The active coating in such products - usually titania - is often very thin, ca. 15 nm on self cleaning glass ,and as a consequence relatively slow-acting under ambient light. However, it is essential that some method is developed to enable a rapid assessment of such coatings - for numerous areas of application, including: R&D, QC, marketing and sales, customer validation and on site, in situ assessment. The only method developed to date utilises an ink that changes colour in a few minutes, upon light activation of the photocatalytic film, when deposited onto a photocatalytic film. This talk will provide a brief overview of photocatalytic films and how they work, followed by a description of the principles of action and features of the inks, along with photos and a movie of the application on various substrates. A brief mention will be made regarding the recent commercial outlet for this photocatalytic indicator technology.

We develop novel block co-polymers for both industrial and domestic applications using technology based on polymer technology. Such polymers can self assemble into micelles which are able to adsorb onto a broad range of substrates including metal, glass, plastic and painted surfaces. These materials are of great interest due to their wide variety of uses, in particular where controlled changes in properties such as adhesion, lubrication, and wetting are required. By carefully tuning the polymer properties using controlled/living radical polymerization (CLRP) techniques we have developed surface treatments which exhibit beneficial properties:

• Prevention / reduction in the build up of dust and dirt. The treatment repels dirt and dust particulates and if they do stick, they are rinsed away easily with water.
• "Streak free finish". Water wets the surface and forms a thin layer, resulting in faster drying and the absence of water marks on the surface.
• Prevention of fogging by the formation of a thin transparent film of water rather than small droplets which refract the light.

We characterize surface morphology of the polymer films using AFM and assess the performance of the treatments in terms of the benefits described above. We describe our in-house testing methods and describe tests and results obtained from an external dust testing facility. The coatings are water-borne and can be applied easily using a variety of methods including spraying, dipping or flow coating.

The effects of nano and micro roughness as well as the chemical composition of surface treatments on hydrophobicity and self-cleaning properties of the coated surfaces were studied theoretically and experimentally. Accordingly, relationships were derived between the interfacial adhesion strength of a liquid drop to a polymer surface of a given composition, the mass of the drop, the measured contact angles and the sliding angle. To verify the proposed model various hydrophobic coatings having different surface nano and micro roughness were prepared using polycarbonate as a substrate. The surface treatment was based on fluoroalkylsilane. Roughness was introduced by means of Silica (microparticle) and POSS - Polyhedral Oligomeric Sil Sesquioxane (hybrid inorganic-organic nanoparticle) using a double morphology topography. In the case of optimal compositions and processing conditions transparent ultrahydrophobic characteristics were obtained. In these cases the contact angle was above 160o and the sliding angle as below 5o. These novel ultra-hydrophobic surface coatings and the associated model were used to develop and design surfaces for a variety of applications such as self cleaning glazing and anti-icing surfaces.

In a joint development of Arcelor/Ocas and Sachtleben photocatalytic active and transparent coatings for metal applications have been developed. The active ingredient is nanoscaled titanium dioxide. After intensive dispersion in the binder system it is possible to get transparent coatings that show a high photocatalytic activity. The sufficient stability of the used binder system for this coating is still a challenge. In this presentation the properties of the coating regarding photocatalytic activity, transparency, weatherability, adhesion and corrosion resistance etc. will be shown.

The efficient stabilisation of nanopowders is a prerequisite for the achievement of highly transparent nanoparticle reinforced polymer coatings. Agglomeration or reagglomeration due to Van der Waals forces can be avoided using different concepts to increase the separation barrier or to decrease the effective Hamaker constant. Extensive studies using silica, alumina and zirconia submicron and nanopowders were therefore performed in order to develop a basic understanding of the mechanism of dispersing small particles either in non-aqueous solvents or in acrylate or isocyanate based lacquer systems. As dispersants different short and long chained organic acids, alcohols and amines as well as comb type polyelectrolytes and various solvents and monomers were compared. The effectiveness of the dispersants was evaluated on the basis of adsorption, zeta potential, transparency and rheology measurements:

Pure steric stabilisation, which is needed in non-polar solvents or in aqueous media with high ionic strength is achieved by adsorbed layers thicker than 10 nm. This condition is fulfilled by different types of comb blockcopolymers or by pentastearic acid derivates or by silanisation reactions. Using these results, highly or totally transparent dispersions of nano-powders in UV curing or two component PU based coatings were prepared and characterized.

Millions of years of evolution have perfected "synthetic" strategies in nature that lead to superior materials and elegant structures. The well-known self-cleaning property of the lotus leaf is due to a combination of proper chemistry and unique multilength-scale surface topography. We have mimicked the dual-scale structure by incorporating raspberry-like particles to polymer films, which have been turned superhydrophobic. Free-energy based modeling reveals the vital role played by the dual-scale surface topography in superhydrophobicity. For practical applications, it is also desirable for superhydrophobic surfaces to be oil repellent; so we further examined the feasibility to achieve oil repellency on structured surfaces. By modifying multiscale structured surfaces with perfluoroalkyl chains, we successfully obtained (super)oelophobic surfaces.

Materials which have weak interaction with the surrounding media (e.g. dirt, bacteria or other contaminants) typically show good "clean-ability" properties due to the presence of low surface-energy groups at the surface. Several approaches are currently available to prepare such surfaces for coatings applications. However, many of these do not sustain low surface-tension upon the damage or wear that result from daily usage. This irreversible loss reduces the materials service-life time, raises maintenance costs and has been retarding the transfer of technology from "laboratory-designed surfaces" to industrial applications.

Therefore the recovery of low-surface energy groups at the surface is critical for the sustainable development of easy-to-clean/self-cleaning coatings. One way to achieve this is to introduce self-repairing mechanisms in the coatings which can replenish the surface with low-surface energy groups after damage. If we learn how to manipulate the chemistry of a polymeric coating to control this recovery, a major step forward will be given which might also lead us to the understanding and control of other self-replenishing mechanisms in different surfaces and polymeric materials to be used in coatings.

A few polymeric systems with low-surface energy groups segregated towards the surface have been investigated. Generally, a high concentration of low-surface energy groups at the surface (~ 20 nm top layer) and low concentration in the coating bulk is desirable. This surface layer is, however, easily damaged in an irreversible way.

Previously, our group reported a new self-replenishing system of cross-linked Poly(urethane) coatings with low Tg (~ 20 °C), which can recover a certain concentration of fluorinated dangling chains, at room temperature, in a surface layer of ~ 5 nm. Our studies are now focused in understanding and controlling the self-replenishing process in this model system, to optimize the recovery response. A dual approach is being followed: experimental and modelling (Dissipative Particles Dynamics, DPD) to investigate the influence of several parameters such as polymer network mobility (as represented by Tg), miscibility of network constituents and dangling ends or temperature effect on the self-replenishing behaviour of the coating. The results obtained with this combined approach will be discussed. Recent results on the application of this self-replenishing polymeric system on low-surface energy structured surfaces will also be revealed.

New easy-to-clean and anti-sticking coatings have been designed for applications at room temperature and for industrial applications at temperatures up to 900°C. The general composition of the coating material is depending on the intended use. The requirements of easy-to-clean or anti-sticking coatings are ranging from low adhesion of limescale, moss dirt or dye, which have to be removed at room temperature, over polymer masses, which have to be demolded at temperatures between 150°C and 250°C up to aluminium parts or casts, which show temperatures between 550°C and 900°C. Beside the primary non-stick functionality of these coatings their long-time stability under drastic thermal or mechanical conditions has to be guaranteed. The results of the development of a non-stick coating used at higher temperature are presented.

A new class of anti-adhesive coating materials has been investigated which can be used to change the wetting behaviour of internal surfaces of machinery used in the food production industry. The systems are based on a polymer binder matrix filled with inorganic nanoscaled particles which provide chemical as well as abrasion stability respectively. Per-fluorinated cross-linkable co-monomers are combined with the polymer matrix in order to decrease the surface free energy of the coating systems in order to minimize fouling. The materials can be coated by spray coating techniques on e.g. stainless steel or even polymers. Two different applications, the thermal treatment of liquid products (carrot juice and milk) and the treatment of powder products such as flour, have been focused in addition to the lab tests on stability.

Artificial superhydrophobic materials which mimic the properties of lotus leaves are typically composed of a low surface energy microstructured layer on a non-superhydrophobic substrate. We have recently found a simple room temperature method to make the surfaces of some metals superhydrophobic in which the samples are immersed in a solution of Au or Ag ions. Electroless displacement reactions lead to formation of a microtextured metallic deposit which is then made superhydrophobic by attachent of a self-assembled monolayer of polyfluoroalkane thiols. The lost cost and ease of preparation makes these materials attractive for large scale applications but their easy accessability means they also provide an excellent platform for studies on novel phenomena associated with superhydrophobicity such as reduced liquid drag.