Trapezoidal sheets are often used as the outer skin of sandwich roofing panels to increase the strength and stiffness of the elements. The coatings can also be flat, with fine or embossed profile (linear, micro-profiled, corrugated, ribbed) and with sinusoidal profile. More recently, products have also been marketed with outer cladding in the form of sheet metal, manufactured from galvanized steel sheet with an aluminum-zinc metallic coating, which can be additionally protected with a thin HPS coating. This provides resistance to high temperatures, corrosion, abrasion, as well as high thermal and light reflectivity.
Specially designed coatings with special properties are also used in sandwich roofing panels, e.g.
HPS 200 – paint coating with a thickness of 200 μm, with corrosion resistance class RC5 and very high durability; especially recommended in regions with high industrial pollution and in coastal areas; polyurethane-based polyamide – with high resistance to corrosion (RC5), scratching and strong UV radiation; very durable (up to 30 years, depending on conditions of use) and recommended for harsh conditions (cold, humid, high UV radiation, industrial and polluted environments);
PVDF (polyvinylidene fluoride or polyvinylidene difluoride) – specialized thermoplastic fluoropolymer with high chemical resistance, providing a coating resistant to corrosion (RC4) and mechanical damage, with high color fastness and fade resistance, as well as high hardness, limiting dirt accumulation and gloss loss; recommended for exterior panel coatings;
HDX Granite – a 35 μm thick special paint coating for agricultural applications, resistant to the aggressive environment inside livestock buildings; corrosion resistance class RC3;
Plastisol – a special 50 μm thick coating for food industry applications, e.g. cold rooms, approved for food contact.
PVC-F – with increased hardness, easily washable and resistant to cleaning products, approved for food contact, recommended for the interior lining of panels for food industry facilities and cold rooms;
laminate – composed of several layers of fiberglass and polyester resin, with high resistance to chemical and biological agents, used as internal coating in panels with PIR foam or rigid polyurethane foam; most frequently used in panels intended for agriculture, e.g. for livestock buildings.
Sandwich panels are factory coated with a protective film to protect the coating from damage, which must be removed within the time specified by the manufacturer (typically up to 30 to 60 days), after the panels have been installed, of course. When exposed to the elements, the film loses its elasticity and cracks, which can make it difficult to remove both the film itself and the adhesive with which it was fixed.
