Binders are macromolecular products with a molecular mass between 500 and ca. 30000. The higher molecular mass products are suitable for physical film formation. With The low molecular mass product, to produce acceptable films, these binders must be chemically hardened after application to the substrate to produce high molecular mass cross-linked macromolecules. Increasing relative molecular mass of the binder in the polymer film improves properties such as elasticity, hardness, and impact deformation, but also leads to higher solution viscosity of the binder. While the usefulness of a coating is enhanced by good mechanical film properties, low viscosity combined with low solvent content are also desirable for ease of application and for environmental reasons. Therefore, a compromise is necessary. The low molecular mass binders have low solution viscosity and allow low-emission paints with high solids contents or even solvent-free paints to be produced. Here, the binder consists of a mixture of several reactive components, and film formation takes place by chemical drying after application of the paint. If chemical hardening occurs even at room temperature, the binder components must be mixed together shortly before or even during application (two- and multi component systems).
The severe demands and accurate performances required for automotive coating are considerable. There is a need for body protection, such as anti- corrosion and stone chip resistance for a durable and appealing finish. Products also have to be appropriate to mass-production conditions and in this respect, must be robust, flexible and economic to use. Thermosetting acrylic-amino resins are used in OEM section of automotive paints and two component isocyanate curable acrylic resins are used in automotive refinishes.
A major substrate encountered in buildings is metal, with ferrous metal being of greatest significance. Whereas wood and masonry are most conventionally grouped under the general heading of building paints, ferrous substrates encountered in virtually all market sectors. Thermoplastic acrylic paints can be used with high gloss retentions and they are easy to use. On the other hand thermosetting acrylic paints with excellent mechanical and physical properties such as high scratch resistance and gloss retention are accessible.
Nearly all the industrial installations, machines and industrial spare parts have to be coated in a protective way. High chemical and physical resistance in severe conditions can be achieved by means of these coatings.
Marine coatings are special- purpose coatings that are supplied to the shipbuilding and repair offshore and pleasure craft markets. The used products are diverse and unique and are formulated for severe climate and immersion conditions. As a result of these conditions, the coatings used must have maximum resistance properties to salt spray and constant sea contact and a broad range of chemicals. Two component iso ciyanate cured acrylic paints are used as finishes on epoxy systems. Due to urethane bonds, they have high environmental resistance especially excellent radiation resistance, which protect epoxy systems from chalking.
Thermoplastic acrylic polymers are used in the decoration and protection of masonry and concrete, for both interior and exterior applications. Due to the highly alkaline nature of most masonry materials, one of the fundamental properties required for high performance long-life coatings on such a substrate is resistance to saponification. Unlike alkyds (polyesters), acrylic polymers have a carbon-carbon backbone which is much less vulnerable to chemical attack. These resins offer very good light-fastness for exterior use and also confer: • Excellent adhesion. • Resistance to mould growth – usually better than water- borne latex systems. • Hydrolytic stability. • Breath-ability – the humidity resident in walls and plasters must be allowed to be released otherwise blistering will result. • Good application properties under adverse conditions such as temperature extremes and damp conditions. In this regard solution acrylic polymers are superior to water based system.
Plastic Coatings Plastic substrates require special consideration because of four major concerns: •Heat sensitivity •Low energy •Surface solvent sensitivity •Flexibility The low energy surface of some polymers can created problems with adhesion. Substrates such as poly olefins, poly propylene and poly ethylene are extremely difficult surfaces on which to achieve proper and sufficient adhesion. Acrylic Thermoplastic paints are used both as base coats and top coats in vacuum metalizing applications on a number of plastic substrates including ABS, HIPS, Noryl and PC. The function of the base coat is to provide a good key between the substrate and the vaporized Al metal and to fill the imperfections of the substrate, thus enhancing the brightness and reflectivity of the deposited metal.
There are two different types of acrylic traffic paints including thermoplastic and cold plastic paints. Thermoplastic Traffic Paints: These paints have excellent adhesion to asphalt and concrete. The paint is applied by conventional lining equipment, must be able to tolerate slight surface wetness and very cold air temperature. Acrylics offer the combination of quick drying, excellent chemical resistance, durability and toughness as well as adhesion to different missionary surfaces. Cold Plastic Traffic Paints: These resins are based on methacrylate monomers which are used for permanent cold plastic marking paints. They are hard, durable, weather resistant and also resistant to some chemicals such as road salts and fuels. The binder contains paraffin which tends to float when stored for a long period of time at lower temperatures. Therefore, it must be homogenized before use by stirring. Tacryl RM965 is the main binder and Tacryl AC100 is used as an activator, which should be added to the paint right before application. This system will be hardened by adding dibenzoil peroxide and it is used for marking pedestrian crossings, stop lines, direction arrows and safety markings with increased night visibility. It’s suitable for manual application with smoothing trowels or draw boxes. Cold plastic materials are usually applied to asphalt and concrete surfaces in layer thickness of 1.5-2.5 mm. The system is totally solvent free so the thickness of wet and dried film is nearly the same. The reaction will be ended after 30 minutes and the coating will be ready to use.
The coating system on wooden surfaces is expected to cope with many different requirements depending on the particular application. What all coating systems have in common is that they must have an attractive appearance and good adhesion between the individual layers of the coating. In the case of interior applications such as furniture and doors, chemical resistance to household substances such as coffee or detergent is also important. Exterior applications such as window coatings, on the other hand, call for a high level of weathering stability and resistance to physical forces such as hail. Both thermoplastic and two component Acrylic Resins are recommended for wood coating.