Substrate Preparation

Spray polyurethane foam can be applied to a wide variety of substrates. Good adhesion between the substrate and the insulation is extremely important. It can be achieved by proper surface preparation prior to the application of the insulation.

All substrates should therefore be clean, dry, and free of grease, oil, loose scale or rust, solvent-free, and other contaminants that may impair the bond of the foam to the substrate. Each substrate must be prepared in accordance with the directions specified by the chemical manufacturer for the application.

1. Wood, Gypsum Board and Fibreboard

The moisture content of wood, gypsum or fiberboard should be less than 19%. Special care should be taken in case of laminates with surface treatment, because the treatment may adversely affect adhesion of the insulation to the substrate.

2. Concrete

Concrete must be dry on surface before applying spray polyurethane foam. If the adhesion is suspect because of high moisture content of the concrete, an adhesion test should be performed.

3. Galvanized Steel

New galvanized steel should be washed with a mineral spirit, then allowed to dry and finally primed.

4. Pre-painted Substrates

The strength of adhesion can vary significantly with the type of paint used. When uncertain, the paint should be mechanically scored or abraded with sand blasting.

5. Bare Steel

The surface must be free of any oil, solvent or other foreign materials as it may affect adhesion. Spray polyurethane foam can usually be sprayed directly onto bare steel after the removal of any loose scale and rust. However, steel tanks must be primed before insulation. The surface should be cleaned with xylene or mineral spirits and then primed. In some cases, to achieve adequate adhesion between the primer and the stainless steel, it may be necessary to sand blast.

6. Aluminum

Aluminum should be cleaned with a mineral spirit. Do NOT use Caustic solution. Aluminum must always be primed prior to the application of the insulation due to corrosion caused by the foam application. After application, acids are formed at the surface between the spray polyurethane foam and the aluminum and they can cause corrosion.

7. Glass

Glass must be clean and dry. Except for cleaning, no special preparation is required for glass. However, when the insulation is applied to the interior of a window, an ultraviolet-blocking coating should be used to the glass prior to application to prevent degradation of the foam from sunlight.

8. Polyvinyl Chloride (PVC)

Washing with a mild solvent, such as mineral spirits, is sufficient to prepare the surface of PVC. Take caution when spraying onto Polyvinyl chloride if the plasticizer content is high. The plasticizer may migrate to the surface of the PVC after the application of the spray polyurethane foam and result in loss of adhesion. Flexible PVS contains the highest amount of plasticizer and rigid PVC the least which is used in pipes – check with building code.

9. Acrylonitrile Butadiene Styrene (ABS)

ABS surface should be cleaned with mineral spirit and primed.

10. Asphalt and Tar

Must be solvent-free when the insulation is applied over it. Must be old enough to assume that there is no solvent present. Spray polyurethane foam should not be applied over fresh asphalt or tar.

11. Polypropylene and Polyethylene

Adhesion of spray polyurethane foam to these two plastics is extremely poor. The only practical way to apply the insulation is to provide some sort of mechanical attachment to the substrate, such as chicken wire.

12. Solvents

The presence of solvents in the substrate or on the surface of it must be avoided. Solvent cured primers and coatings must be allowed adequate time to cure to allow complete solvent evaporation.

13. Spray Polyurethane Foam

Areas that show ultraviolet degradation should be cleaned by wire brushing prior to the application of more insulation.

14. Earth

Must be dry and firm. No special requirements are needed when installing spray polyurethane foam in contact with earth. The manufacturer shall be consulted in cases where a hydrostatic pressure will be exerted on the spray polyurethane foam.

15. Modified Bitumen Membrane

The membrane must be adhered to the substrate. The installer must confirm with the membrane manufacturer that the product has been installed properly.