Thermal properties of a sandwich construction insulated with Polyurethane (DC-System)

Rigid polyurethane foam (PUR) is a good thermal insulation product for buildings, mainly due to its low thermal conductivity (λ ≈ 20 mW/m.K), low permeability to water and stability over time. The other types of insulation products available on the market have a significantly higher thermal conductivity: + 50% for expanded polystyrene (λ ≈ 30 mW/m.K), + 75% for mineral wools (λ ≈ 35 mW/m.K), etc. Despite its low thermal conductivity, polyurethane foam (PUR) is not much used as insulation material for walls because of its low resistance to fire. The most common PUR boards are classified C-s2-d0 until E [1] (reaction to fire according to EN 13501-1), which means that they are from moderately to very inflammable, with a limited smoke production and no droplets. The PUR foam has a relatively low flash-ignition temperature (around 300°C [2]). Therefore, the PUR foam needs to be associated with another material to provide the necessary fire resistance. Two materials have been tested: gypsum fibre boards and cement-based boards. The reaction to fire of the gypsum fibre is A2-s1-d0 (almost not inflammable), and an 18 mm thick board provides a fire resistance of 30 minutes. The gypsum fibre can resist to temperature as high as 800°C without major structural changes [3]. The challenge of this project consists in the association of the two materials.

The study will be based both on numerical models and experimental tests (small and large scales).