Latest-Generation Waterproofing Coatings: Polyurea

In 1961, Raf Van Gorp founded Ravago's first facility, a plastic waste recycling plant, marking the company's entry into the sector, and began selling plastic resins. Today, Ravago operates globally with 31 production facilities, serving more than 40,000 customers across 230 offices in 57 countries with nearly 6,000 employees. Ravago Petrokimya Üretim A.Ş. manufactures thermoplastic elastomers, engineering plastics, silicone elastomers, EPS, thermoplastic polyurethane and polyurethane systems. Tekpol, the polyurethane systems house within Ravago Petrokimya Üretim A.Ş., specializes in rigid polyurethane systems, discontinuous panel (DCP) polyurethane systems, continuous panel (CP) polyurethane systems, spray polyurethane systems, flexible polyurethane systems, molded flexible polyurethane systems, molded foam systems, integral skin systems, viscoelastics, semi-rigid products, RIM, filter systems, shoe and sole systems, C.A.S.E (coatings, adhesives, elastomers) and polyurea systems. Under the Tekpol umbrella of Ravago Petrokimya Üretim A.Ş., polyurea coatings production began in recent years. This coating type has become a recent sector trend, replacing epoxy and polyurethane coatings due to its physical and chemical properties, ease of application, and time-saving advantages. Before discussing the characteristics that distinguish polyurea coatings in the sector, let us introduce the product: polyurea is a coating system composed of a mixture of isocyanates and polyamines, applied by spray method, and used on many surfaces with the desired application thickness.   Urethane bonds are formed from the reaction of the isocyanate group with polyol, creating the polyurethane structure. Similarly, urea bonds are formed from the reaction of an isocyanate prepolymer with –NCO end groups and polyamines, creating the polyurea structure. Polyurea coatings come in two types: pure and hybrid. Pure polyurea products result from the reaction of isocyanate with polyamine blend. Hybrid polyurea products are obtained from the reaction of isocyanate prepolymer with polyamines and polyols in the presence of catalysts and additives. Pure polyurea products are significantly advantageous compared to hybrid polyurea, polyurethane and epoxy coatings due to their chemical structure and morphology. Polyurea products are known in the sector for their fast cure rate, waterproofing, insensitivity to moisture, excellent chemical and mechanical properties, seamless application, resistance to extreme weather conditions, high wear resistance due to flexible structure, and many other excellent properties. In accordance with all these properties, they can be applied in many areas: concrete, metal, wood, PVC sheets, decorative and swimming pools, parking garages, ceramic surfaces, roofs and balconies, bridges, vehicle bodies, military vehicles, etc. During polyurea application, certain factors affect final quality. One of these factors is machine conditions. Due to polyurea's fast cure time and short mixing duration, high-pressure machines are used, and these machines perform a 1:1 volumetric mixture. For effective mixing and application, component temperatures should be 75–80°C and pressure around 180 bar. Since the polyamine blend contains various chain extenders and pigments, thorough mixing is necessary before application to prevent settling. Another important factor to consider in polyurea applications is surface preparation. Before application, ground conditions are examined to ensure the surface is free from moisture, dirt, rust, oil and grease. Subsequently, the first step is applying a primer coat. This primer penetrates into the concrete, helping to seal pores and cracks. Before and after the primer application, mastic application is also performed to seal cracks.

Figure 1. Evocoat Pure 5503-700 floor application

After this stage, silica sand is added in a certain proportion to the two-component epoxy primer and applied to the surface with a squeegee. This application fills voids in the surface and provides adhesion. If needed, a second two-component epoxy primer without sand is applied, bringing the product to optimum conditions for polyurea application. Depending on surface conditions, 1–2 kg of polyurea per square meter is applied. Since the product has an aromatic structure, it will yellow after prolonged exposure to sunlight. To prevent this yellowing, a two or single-component UV-resistant aliphatic polyurethane topcoat is applied depending on demand.

Figure 2. Evocoat Hybrid 5503-450 floor application

Due to the amines in polyurea's structure, it reacts faster than polyurethane and epoxy coatings, allowing the application to be put into service quickly. Moreover, it requires no catalyst and its insensitivity to moisture prevents reaction with water, eliminating carbon dioxide gas generation and preventing air bubbles and adhesion failures in the floor. Due to its flexibility, it can support virtually any type of load. Its lack of solvents and odorless nature, as well as its long-lasting durability, have established polyurea as an indispensable product in the sector. Elif Öz Çetin Research and Development Engineer Ravago Group