The good properties and protective ability of polyureas are attracting growing market interest in protective coatings. Polyurea applications such as waterproofing, corrosion protection, chemical and abrasion resistance are used in many areas of human activity. In the past three decades, polyurea application technology has been widely developed in many countries and tested in all climatic conditions. Numerous tests have been performed and considerable experience has accumulated in the operation of polymer spray coatings. Constantly looking for new possibilities for applications of using Hot spray polyurea materials
Polyureas can be applied wherever durable, effective and environmentally friendly waterproofing as well as protection against wear and corrosion. Below we will briefly introduce the basics of polyurea technology and the features of spray coating on major types of surfaces.
Polyurea’s application is significantly different from other surface protection methods. Apply Polyurea evenly through a heated, multi-component, high pressure reactor spray device, capable of supplying raw materials at paint spray guns at a minimum spray pressure of 2000 psi and object temperature Material is 60-80ºC. The polyurea layer is usually at least 1mm. The polyurea injection process is highly productive and allows you to do large-scale work in a short amount of time. Due to technological features, polyurea spray can be applied in places where other systems cannot be used: existing production, complex surface configurations, route conditions, adverse natural factors ( temperature, humidity).
Application Polyurea equipment
The high pressure devices manufactured today are specially developed for polyurea application technology and, as a rule, are not common equipment for wide use. A prerequisite for a good quality polyurea coating is the good mix of the two components. Because of their high reaction rate, mixing must take place in a very short time. A special two-component spray system (eg Graco or Gama) provides an accurate dosing of the components.
Polyurea application systems are high-tech equipment, expensive and require qualified maintenance. The unit is relatively compact and, together with an air compressor, can be mounted in a van barrel. The large length of the heating pipe (up to 90m) allows the mobile assembly to be quickly deployed on-site with minimal movement of the equipment and the component case.
Before starting polyurea application, measures should be taken to prevent polyurea components from spraying onto nearby windows, vehicles, equipment and other surfaces.
Application of polyurea to concrete
Protecting and waterproofing concrete by applying polyurea is a very common job. Thanks to the advantages of seamless polymer elastomer, polyurea is effectively used for roofing, waterproofing the foundation, protecting tanks, floors, covering swimming pools and protecting any concrete structure.
Before applying polyurea to concrete, it is necessary to carry out some preparation activities. First of all, all dirt, defective and weak concrete surface should be removed from the surface. The cleaned concrete floor must be dry (no visible moisture, moisture not exceeding 8%). If there are large cavities, potholes and debris in the concrete, its surface should be filled.
If the condition of the vertical surface is not satisfactory, a high-strength repair grout may be required prior to application of polyurea.
Its main purpose is to close relatively large voids present on the concrete surface. For high demands on decorative properties (eg, surface finish of swimming pools), care should be taken to smooth out the plastering. The standard thickness of the polyurea coating is 1.5-3 mm. The application of polyurea can only conceal minor defects made during the preparation. After construction, the leveling and filling layers must be cured to a full ripeness and moisture content as indicated for use.
After the preparation work is completed, the plastering wall and the concrete surface of the floor must be primed one or more layers to increase the adhesion strength better and to overlap the voids. The primers, which penetrate the surface porosity, not only insulate the pores but also form a durable composite component that protects the applied polymer coating from the moisture of the substrate. One and two component inoculants based on epoxy and polyurethane resin, compatible with polyurea, can be used as a primer. The applied primer must be cured until fully cured according to the instructions. When applying polyurea without pre-priming or with incorrectly selected priming ingredients, potentially breaking the polymer’s adhesion and hardness. Air and moisture, voids of concrete or other porous substrates (plaster, cement, foam concrete, brick, wood) are displaced during the use of polyurea. This process leads to the formation of defects in the form of craters and even holes.
The application of polyurea is carried out on a concrete surface prepared according to the procedure described above, in one or several layers, depending on the required thickness. The specifications and service life of the protective coating depend directly on the correct compliance with the polyurea application technology and surface preparation.
Application of polyurea to metals
Application of polymers to metals is often carried out for corrosion protection of metal products and protection against wear. Polyureas have been used successfully to protect main pipes, metal structures, vehicle tanks, tanks, pump stations and other equipment.
Before applying polyurea to metal, dust, corrosive and scale products should be removed from the insulation surface and welded seams should be sanded.
One of the most effective preparation methods is to clean bare metal surfaces by spraying abrasive grains with sand, steel beads or corundum. In the absence of machinable steel abrasion, it is permissible to mechanically clean with abrasive tools to adhere to rust and scale. After mechanical cleaning, the surface should be cleaned by blowing dry air and degreasing with a soft cloth leaving no fibers on the surface, wiping the surface with acetone, xylene or toluene. To ensure a better adhesion of the insulating coating to metal surfaces, primed with a special primer (adhesion accelerator) is recommended. After the primer has dried, the polyurea layer is applied.
The time from the end of surface cleaning to the start of polyurea application should not exceed 4 hours. If the specified time is exceeded, condensation can form on the surface of the product, which should be heated with a gas burner or blown hot air to remove. It is also important to ensure the cleanliness of the prepared surface, which does not allow dust and pollution. If the surface is prepared by abrasive cleaning (sandblasting) the surface preparation and polyurea blasting processes should be isolated, because During abrasive machining, a large amount of dust is generated, This is not desirable for polymer coating processes.
A prerequisite for a successful application of polyurea to the steel surface is that the metal temperature exceeds the dew point by at least 3 ° C, which ensures no condensation. Polymer coatings are applied in one, two or more layers. In case of applying one layer at a time, the interval between two successive layers should not exceed 24 hours, otherwise additional surface preparation is not required.
Curing time of polyurea is about 15 seconds, after 1 hour, metal products with polymer coating can be shipped in store. Can start working after 1-5 days, depending on the coating brand.
Application of reclaimed polyurea on an old roof
Polyurea spraying is an effective method to repair existing roofs, in most cases allowing work to be carried out without dismantling the existing roof. The high productivity of the technology and no dismantling of the building allows for short-term roof repairs. Polyurea roof repairs are also effective in cases where previous roofs contain moisture. The vapor permeability of polyureas contributes to the release of excess moisture over time.
The degree of preliminary surface preparation depends on the condition of the roof. If the old coating is in satisfactory condition, preparation for this coating is reduced to clean the coating from debris and dust. In other cases all flaky and defective areas must be opened or removed prior to applying polyurea. Of course, roofing with polyurea repairs is possible with a certain degree of damage to the roof; it is not possible to restore a completely destroyed roof just by applying polyurea. Normally, in case of severe damage, it is necessary to restore the insulation, sprayed polyurethane foam such as APS-28 can be used.
Polyurea has good adhesion to most rolled materials (membrane) or red brick, however, to reinforce the base of the old coating, to create uniformity, to dust and heal minor cracks, Before spraying polyurea, the cleaned old surface should be covered with a primer of specific choice. After the primer has cured, a layer of waterproof polyurea is applied over the entire roof surface.
Application of polyurea to polyurethane foam (PU Foam)
During the development and implementation of polyurea-based sprayed coatings, one of the first tasks was to coat a protective layer on foam insulation. Polyurethane foam (PU-Foam) is a modern effective insulation material with many advantages and is increasingly used in popular construction. PU-Foam is applied by spraying onto surfaces of any complexity, completely filling all irregularities, joints, gaps and voids, creating a monolithic seamless insulation.
Usually polyurea is used to protect polyurethane foam and to create a roofing that has full functions: insulation, waterproof, wear-resistant and UV-resistant. This new technology for installing and repairing old roofs (PU-Foam plus polyurea) has become popular in Europe, the US and many developed countries.
After spraying the PU-Foam insulation, after several hours required for the reaction and cool down then cover with a protective waterproof polyurea with a minimum recommended thickness of at least 1.5 mm. Due to the specificity of the polyurethane foam surface, when polyurea is applied, minor defects in the form of bubbles or holes can occur. These deficiencies can be avoided by the following actions:
- Application of high quality (high density) sealed polyurethane foam with a dense structure
- The use of special soils helps to improve the surface of the PU-Foam
Application of polyurea on the surface of sheet material
The use of polyurea as a quick coating on assembly projects, 3D printers … is a modern solution and has clear advantages for construction. The use of polymer coatings further optimizes the construction process for fast and reliable results. Let’s highlight the particularly important advantages in this section:
- The working speed when spraying polyurea is completely consistent with the concept of building assembled houses, 3D printing houses …
- The adhesion of polyurea to the surface of many different materials allows you to work directly on the surface of the sheet
- Get a surface finish by coating polyurea in one go with no additional work required
- The physical properties of the coating are significantly superior to that of today’s traditional roofing materials.
- The need for mandatory moisture control of the sheet material to avoid coating defects during polyurea application
- Monitor surface condition, preliminary removal of large defects and crevices
- Pay special attention to the aesthetic appearance of the resulting surface. Because polyurea is used as a complete protective coating, sagging and smearing should be avoided during application.
Polyurea application for smooth surface and light absorbency
When applying polyurea on surfaces with low absorbency (ceramic tiles, resins, fiberglass, varnished wood, painted surfaces), to improve adhesion, epoxy primers or acrylic primers should be used. , have different viscosities and contain crude fillers in their composition. These materials have many advantages: friendly to the environment and dry quickly, easy to apply on both floor and wall surfaces. Once completely dry, they form a rough surface that gives good adhesion to sprayed polymer preparations.
Repair polyurea coating
A need for reconditioning of polyureas on existing polymer coatings may arise. For example, when repairing an coating or device to contiguous a new application location with an existing coating. Cold Polyurea is used in small locations with the ease of application by hand. In addition, to ensure the adhesion between paints, special primers are required according to manufacturer’s requirements