In terms of properties, the main difference between PUR/PIR sandwich panels lies in their composition. The foam obtained with PIR (Polyisocyanurate) systems contains a high degree of aromaticity due to the formation of the polyisocyanurate structure, providing a higher thermal stability compared to urethane (PUR) groups, thus improving its fire resistance.
The PIR foam reacts safely to fire by forming a carbonised surface layer that protects and prevents the penetration of fire into the inner layers. In the composition of PIR panels, as a general rule, there is a lower concentration of flame retardants than in PUR panels, thus generating less smoke during combustion. There are even PIR panels on the market that are free of halogen flame retardants.
Even so, the products must be tested to determine their fire behaviour with the reaction and fire resistance test methods according to current regulations depending on the location.
In terms of thermal properties, PIR remains stable in a higher temperature range than PUR.