Polyurethane Injection Foam and Its Applications

Polyurethane is a polymeric material obtained from the reaction of an isocyanate and a substance containing hydroxyl groups. What makes this material highly valuable is the very rapid nature of the reaction within seconds and the product's resistance to environments with different pH values.

Figure 1. Interaction of polyurethane material with water and foam production

Depending on the polyurethane structure, it provides good water resistance, toughness, abrasion resistance, light resistance and chemical resistance. In polyurethane applications, the ratio of isocyanate and hydroxyl must generally be controlled carefully. When polyol or isocyanate is reactive and cross-links form, it will not be necessary to achieve the exact ratio.[1]

Figure 2. Usage rate of polyurethane material in different sectors.[2]

Concrete structures commonly suffer from cracking, a defect frequently encountered in new buildings as well, though it is generally influenced by aging and fatigue in older structures. Crack formation leads to water leakage, which depending on circumstances affects the structure's strength and can cause service disruptions. Polyurethane injection foam is one of the most preferred methods to prevent water leakage and resolve these issues. This method is particularly the only option we can use when there is no possibility to access behind the crack where water is leaking and when water flow must be stopped from the opposite direction to where it exits the surface.

Figure 3. Crack and water leakage in a dam wall

This material, generally used for repair purposes, is similarly used in tunnels, metro stations, bridges, water and plumbing sewage systems, water tanks and dams, as well as in building basements to prevent water leakage.

Figure 4. Cracks and water leakage in a water tank.

For this purpose, holes are drilled at appropriate intervals around the crack at approximately 45 degrees to the crack surface and positioned to reach the material behind the water-bearing layer (cutting through the crack at half the wall width). [3]

Figure 5. Cracks in a building and injection foam application

The spacing between holes is approximately equal to the wall thickness and should be positioned diagonally. Packers, which are anchors, are placed in the holes and the injection material is forced into the cracks with the aid of a special injection pump. The injection material reacts with water and moisture to form a flexible foam, beginning to seal the cracks and prevent water leakage. The process continues until water in the crack is completely replaced by material and/or foam. To provide higher durability and longer-lasting water resistance, even after foam forms, the material must continue to be injected until quality foam is produced. In vertical cracks, the direction of material injection should be from bottom to top, and after injecting material through every three packers, the process should be repeated and in some cases material may need to be injected in three or four stages. [4]

Figure 6. Spacing between holes and application direction in injection foam application

Expected Properties of the Material:

• Provision of permanent water resistance (flexibility and quality continuity of the final product), • Ease of use (low viscosity), • Visibility and controllability of the material, • Rapid reaction and curing (controllable by catalyst ratio).

Advantages of polyurethane injection foam over competitors:

• Provides better water resistance. Because epoxy materials are rigid, they can cause cracking and damage in concrete structures, but polyurethane injection foam, being flexible, adapts to the base material and structure without damaging joints or causing deterioration. • It is a much more cost-effective method. It is an excellent solution that can be applied with very low investment without the need for water drainage and without causing any service disruptions. • Provides very rapid solution. It is a method that can be applied without any pre-treatment, underwater and without even requiring cleaning. [5] • Due to this method and similar advantages and with the development of the construction sector, further growth of the sector is expected, and total market size between 2017-2024 is expected to grow from USD 7 billion to USD 11 billion. Countries such as China, India and Mexico are expected to play a major role in this expansion. [6] As PURİN Polyurethane, we present our high-quality injection products to our domestic and international customers in order to meet market needs and at the same time contribute to the country's economy. Asghar Najafigharehtapeh International Sales Manager PURiN Polyurethane     Sezer Keskin Domestic Sales Manager PURiN Polyurethane     Sources 1. http://www.wernerblank.com/polyur/learning/learning_center1.htm webpage 2. http://www.essentialchemicalindustry.org/polymers/polyurethane.html webpage 3. Water Control using polyurethane resins. Zamacois Eduardo, Resinas y Equipos S.L., 9th INTERNATIONAL MINE WATER CONGRESS 4. https://sealboss.com/chemical%20injection%20foam%20grout%20spec.pdf webpage 5. Using Polyurethane Grouts to Seal Seepage Cracks Underwater, Research. Update Summer 2016, Bulletin 2016-12 6. Aniket Sharma. Waterproofing Chemicals Market | Trends, Growth & Forecast Research Report 2018-2025. https://www.researchgate.net/publication/330853879