Excellent flame retardancy to cope with stringent fire restrictions
Due to more stringent fire restrictions, sandwich panel manufacturers have to develop high-performance products while keeping up with increased regulation.
In order for sandwich panels to be usable for construction purposes, they must comply with certain requirements concerning reaction to fire. In the context of European harmonization, it has become a requirement for standards to be unified and now the valid European standard is EN 13501-1.
Most of the European countries have adopted this new standard and consequently the adhesive which is used for the assembling of the in-core and out-core materials has to comply with Euroclass A2, which is a fire class within the much broader EN 13501-1.
To comply with Euroclass A2, the calorific value of the adhesive joints must not exceed 4 MJ/m2 . Commonly polyurethane adhesives have a calorific value of approximately 30-35 MJ/kg, thus leading to a maximum adhesive coat of 115 g/m2. For ensuring cohesive bonding of the inner core and outer skin elements and a long-lasting durability of the panel, an adhesive amount of at least 140-150 g/m2 is normally required.
There are many approaches to adhesive technology in order to minimize either the calorific value of the adhesive, or the amount of it, in order to comply with the maximum 4MJ/ m2 calorific value of the adhesive joint. Attempts at lowering the calorific value of the polyurethane adhesive is quite challenging since the processing of the adhesive shouldn't be negatively impacted, and the glue still needs to be compatible with the existing lay-down techniques in use at the customer's facility. Reducing the amount of coated adhesive per m2 is a straight forward solution to enhancing the performance of the adhesive without compromising the adhesion performance.