Primerinox® coated sheets are made of series 300 or 400 stainless steels which have been treated on a coil coating line by applying special organic primers.
These primers simplify and increase the duration of the adhesion of insulating foams or structural adhesive films.
Importance of the interlayer adhesion in insulating panels
It is of paramount importance that the various layers of structural and / or insulating sandwich panels should be bound homogeneously and permanently.
Indeed, partial adhesion zones or adhesion loss in time could result in:
- Decreasing rigidity of the panel and structural brea
- Aesthetical defects (waviness, dew stains etc).
- Localized corrosion initiation spots.
It should be noted that mechanical and chemical stresses could weaken the rigidity and mechanical resistance of the panels:
- Mechanical deformations with shear forces higher than the adhesion forces.
- Periodic, repeated mechanical and thermal stresses (vibrations, thermal expansion).
- Water or corrosion agents absorption, which could be present either in the cellular material or in the work environment, and which could migrate to the steel interface.
Thermo-insulating foamed panels
When manufacturing sandwich panels foamed with products applied in the liquid state, metallic surfaces which are exposed to foams should present the following properties:
- Low wetting tension, to ensure an uniform distribution of the resins during casting and nucleation of the foam.
- Chemical affinity with foaming resins, to ensure sufficient adherence.
- Chemical stability and resistance to corrosion, to ensure a long lifespan.
The excellent corrosion resistance of stainless steels and the special primers used in the production of Primerinox® sheets fully comply with these requests, thus offering a much longer lasting adhesion than what could be expected from other base materials or from stainless steel sheets with brushed or polished surfaces.
|Property||Reference AISI 304 polished||Transparent Primerinox||Coloured Primerinox|
|Primer thickness||4-5 µm||5-8 µm|
|Hardness (ECCA T4)||F/H||H/2H|
– Bending (ECCA T7)
– Drawing EN-ISO 1520
|Impact resistance (ECCAT5)||10 J (Ok)||10 J (Ok)|
|Adhesion to PU foams (*)
a. Dry adhesion (after 24h)
|Adhesion loss 10-15%||Ok – Cohesive rupture in the foam||Ok – Cohesive rupture in the foam|
|b. Adesione dopo permanenza in camera climatica (40°C, 100% di umidità – dopo 24h)||Adhesion loss 100%||Ok – Cohesive rupture in the foam||Ok – Cohesive rupture in the foam|
(*) PU DOW Voracor Polyol 7351 / Isocyanate526 (reference)