How to protect PUR foam against UV radiation and water?

Closed-cell PUR foam is a very popular material used to insulate flat roofs from the outside. The application involves applying foamed polyurethane to the roof surface by spraying it with a special gun. After spraying, the foam swells and hardens, obtaining its final form. PUR foam has many advantages - it creates a continuous, homogeneous structure, so there are no joints or thermal bridges. It will work well when covering surfaces with unusual shapes, because the spray can reach all nooks and crannies and provides excellent thermal insulation - the thermal conductivity coefficient λ for this material is 0.021-0.024 W/m·K.

However, PUR foam is not resistant to UV radiation, therefore it cannot be used as a final coating on a flat roof. It should be surface-protected with an appropriate waterproofing liquid membrane that will "cut off" sunlight and be resistant to possible water stagnation.

Neoproof PU W-40 – one-component, water-soluble polyurethane membrane

Neoproof PU W-40 is a liquid polyurethane waterproofing membrane. Easy to use - the product is water-soluble and single-component. Creates a tight, uniform coating. It can be applied with a traditional roller or spray. The coating is fully resistant to water stagnation and UV radiation. The elasticity of the hardened coating is as much as 250% (elongation at break, at a force of 3 MPa).

Before applying Neoproof PU W-40, the PUR foam should be primed with Revinex , diluted with water in a ratio of 1:4. After 2 hours, apply the first layer of membrane. Then, after 24 hours, we apply the second layer. Theoretical material consumption per 1 m2 should not be less than 1.2 kg/m2.

Neoproof Polyurea C1 – two-component solvent-based polyurea membrane

Neoproof Polyurea C1 is a modern, two-component polyurea waterproofing for cold application. Unlike polyureas applied with a special hot unit, this membrane can be applied with a traditional roller or airless spray.

The product is a two-component product (base + hardener). Before application, the ingredients must be combined and mixed thoroughly with a low-speed mixer. From now on, we have about 90 minutes (at 23°C) to use the product, after which time it hardens and sets. The elasticity of the hardened coating is 410% (elongation at break, at a force of 9.8 MPa).

As in the case of Neoproof PU W-40, we obtain a uniform, tight coating, fully resistant to water stagnation and UV radiation. An additional advantage of this product is the fact that rain can fall on the coating after just 2 hours! This is a very important parameter in case of uncertain weather.

Other features that speak in its favor are:

• application directly onto closed-cell PUR foam, without primer
• application in one layer (“C1” in the name comes from the English “one coat”)

These two factors result in faster completion of the work - there is no need to return to the construction site to apply subsequent layers.

What if we are dealing with old PUR foam on the construction site, painted with other coatings?

No problem! Most often it will be one of the following situations:

• Old coating in good condition, requiring refreshing

We wash the roof thoroughly and then leave it to dry. Neoproof Polyurea C1 is applied directly, and Neoproof PU W-40 is applied after priming the surface with diluted Revinex.

• The old coating is peeling, the PUR foam has been partially "eaten" by solar radiation or is mechanically damaged and has open cells.

In this case, we also wash the roof thoroughly and leave it to dry. The flaking parts of the old coating will fall off. Most likely, the foam will have open pores in these places. In such a case, we recommend choosing Neoproof Polyurea C1 , which is applied after priming these places with water-soluble epoxy primer Acqua Primer NP .

Closed-cell PUR foam is a modern solution for roof thermal insulation. Combined with one of the described liquid waterproofing membranes, it will provide excellent roof protection and peace of mind for many years.