Chemical differences, performance, and selection criteria
Introduction
When undertaking roof rehabilitation, choosing the right waterproofing system is a critical decision. Among the most advanced solutions on the market, polyureas stand out for their durability, elasticity, and ultra-fast curing times. However, within this family there are two main variants—pure polyurea and hybrid polyurea—which, although similar in appearance and application, have substantial differences in both their chemical composition and long-term performance.
In this article, we analyze their characteristics in a technical and comparative way to help you select the most suitable option according to the type of project, climate, and service requirements.
What is polyurea?
Polyurea is a two-component elastomer formed by the reaction of an amine (component A) with an isocyanate (component B). The result is a continuous, joint-free membrane with high chemical and mechanical resistance, capable of adapting to any support geometry. Its application by hot spraying allows for instant curing, even in extreme temperature or humidity conditions.
Its success in roof rehabilitation is based on three key factors:
- Fast application: ready for use in minutes.
- Permanent elasticity: over 400% elongation.
- Direct adhesion to a wide range of substrates (concrete, ceramic, metal, polyurethane foam, etc.).
Pure polyurea: the highest standard
Pure polyurea is obtained exclusively from the reaction between isocyanates and amines, without the involvement of polyols.
This seemingly minor chemical detail has a major impact on its final performance:
- Instant curing (<10 seconds): ideal for projects where commissioning time is critical.
- Extreme moisture resistance: can be applied even on slightly damp surfaces without the risk of bubbles forming.
- Superior thermal and UV stability, especially when formulated with aliphatic systems.
- Consistent durability and elasticity, even after years of exposure.
For this reason, it is used on exposed roofs, critical infrastructure, in the chemical industry, and in storage tanks where continuity and absolute impermeability are essential.
Its main disadvantage is its higher cost and the need for high-pressure and high-temperature spraying equipment, which requires specialized personnel.
Hybrid polyurea: balance between performance and economy
Hybrid polyurea combines isocyanates with a mixture of amines and polyols.
This modification reduces the reaction speed and lowers the cost of the formulation, while maintaining most of the mechanical properties of pure polyurea.
Its main advantages:
- More competitive cost, while maintaining good waterproofing.
- More controlled application (slower curing), useful in medium-sized projects or in variable weather conditions.
- Good adhesion on most substrates with suitable primers.
However, it has some limitations:
- Lower thermal and UV resistance, so it usually requires a protective finish (e.g., an aliphatic polyurethane top coat).
- Greater sensitivity to moisture during application.
- Slightly lower durability in environments with high exposure to sunlight or chemicals.
In practice, it is an excellent alternative for non-trafficable, industrial, or residential roofs, where the cost-performance balance is decisive.
Technical comparison
| Property | Pure polyurea | Hybrid polyurea |
|---|---|---|
| Composition | Isocyanate + Amine | Isocyanate + Amine + Polyols |
| Cured | Instantaneous (5–10 sec) | 10–40 sec |
| Elasticity | >400% | 300–400% |
| UV resistance | Very high (aliphatic) / medium (aromatic) | Medium (requires top coat) |
| Application | High pressure, high temperature | Lower equipment requirements |
| Wet adhesion | Excellent | Limited |
| Cost | Taller | More economical |
| Recommended use | Exposed roofs, industry, warehouses | Non-trafficable or maintenance roofs |
Discover our polyurea solutions or speak with a Krypton technician to find out which system is right for your project.
