Polyurethane varnishes and their use

In addition to paints based on polyurethane, polyurethane varnish is widely used in everyday life. It is produced in various compositions and allows not only to raise the aesthetic impression of the surface treated by it, but also to extend the period of use of wooden furniture and the interior of the home.

Content:

• Classification of compounds
• Chemical composition
• Appearance
• Application technology
• The benefits of woodwork
• Work technology
• Aerosol form
• Application by roller or brush

Classification of compounds

The products in question can be classified according to the following indicators.

Chemical composition

Compositions are available on a one- and two-component basis. One-component water-based varnishes are a composition that is completely ready for use. It can be used in liquid form and applied in the traditional way - with a roller or brush.

For repairs on a limited surface with accelerated drying, it is much more convenient to use a single-component varnish in the form of a spray. The aerosol can, after shaking, is sent to the reconstructed surface area, and after a few moments the coating is ready.

A two-component composition is prepared immediately before use, for which the base and hardener are thoroughly mixed. This option is more suitable for processing large wooden surfaces, however, the capabilities of the worker should be clearly calculated, since already mixed components are viable for a very limited period of time (no more than 4-5 hours).

Appearance

The coating can be glossy or matte. There is no difference in the quality of adhesion to the base, but scratches will be more clearly visible on the glossy surface. Therefore, it is better to limit the use of a substance that gives a glossy base to surfaces that should not be very wear-resistant and do not undergo strong mechanical stresses.

Matte varnished surfaces look better in rooms with diffused daylight. In addition, the matte surface better hides defects of insufficiently qualified varnishing.

Application technology

Polyurethane varnishes can be without the self-leveling property and with it. It is much more convenient to work with self-leveling (having a higher density and viscosity), since after application the surface becomes more uniform. Transparent polyurethane varnish will be uniquely self-leveling.

The benefits of woodwork

Unlike alcohol-based varnishes, polyurethane compounds are made on a water basis, and therefore are significantly less toxic. At the same time, they should be applied in several layers (greater volatility of the solvent affects).

Waterborne polyurethane varnishes are enough to apply in one or two layers.

Despite the slightly increased drying times, they eventually firmly adhere to the wooden surface, which becomes very wear-resistant.

Water components are the reason that they can be combined when processing wood with acrylic paint. In this case, the surface will not be colorless, but its appearance and strength properties will improve. A clear polyurethane varnish prepared using an aqueous base cannot be combined with polyurethane alcohol-based varnishes and paints.

Of the consumer benefits of the substances under consideration, the following should be highlighted:

1. Waterborne varnishes do not have the property of increased surface tension, and therefore, after drying, they are not prone to crack formation of the layer applied to the wood.
2. Since after application, the composition is intensively polymerized, then its subsequent peeling does not occur.
3. High elasticity and wear resistance of polyurethane as a basis contributes to the durability of the final coating.
4. Regardless of the type and method of application (spray or liquid composition), polyurethane-based substances are highly resistant to media with chemical aggressiveness properties, as well as ultraviolet radiation.

Work technology

The choice of a suitable type is determined by the nature of the covered surface and its size. The initial surface is best cleaned from dust and dirt, and work is done in the absence of drafts.

Aerosol form

The type of varnish determines the complexity of the work. It is best to handle small-sized objects using aerosolized varnish. According to the instructions, the spray is applied to the surface, after which it is kept for an hour at constant temperature and humidity.

For uniformity of the subsequent drying of the final coating, the spray flow is directed uniformly and at approximately the same speed. Since the consumption of the composition will be increased for the spray, stock up on an additional spray can from the same batch.

Application by roller or brush

Working with one-component or two-component polyurethane varnishes is somewhat more difficult. To facilitate the work of applying the coating, it is better to dilute the one-component composition with a solvent, and when using a roller or brush, its amount cannot be more than 4-5% of the volume of the main component. The final consistency should be comfortable for varnishing.

A two-component varnish is best applied only with a soft roller - such a tool works faster, and a prepared but not applied composition will not have time to set.

Remember: a repeated attempt to use an already solidified mass, even when diluted with a solvent, will fail.

The second layer is not applied immediately, but after the previous one has completely dried. The coating properties during multilayer varnishing are not improved, therefore, multiple coating of the surface with water-soluble polyurethane varnish is not performed.

Which application technology to choose depends on the properties of the product itself: for example, for a self-leveling composition, the length of the time interval between varnishing does not really matter. At the same time, in other cases, the final surface may be uneven, it will need to be cleaned with an emery cloth, which means that you will have to forget about the glossiness of the coating.

When choosing which varnish is more appropriate to apply, it is worth remembering that the polyurethane coating turns yellow over time. In addition, when decorating wooden coatings in children's rooms, it is better to use other, more environmentally friendly varnishes with the same properties. Also pay attention to the initial viscosity of the composition: the usual norm is from 30 to 75 centistokes, and large values ​​correspond to glossy brands.