Polyurethane insulation is lightweight but strong, with a density ranging between 30 kg/m³ and 100 kg/m³ depending on the application. For special applications that are subject to extreme mechanical loads, the density of the PUR/PIR rigid foam can be increased to 700 kg/m³.
Even at low densities, polyurethane keeps excellent mechanical properties such as compressive stress, compressive strength and creep. These properties are essential in load bearing applications, such as floorings and other areas that can be subject to regular foot traffic such as flat roofs.
If PUR/PIR rigid foam is used for thermal insulation in flat roofs, interior finishing or in the external thermal insulation composite system (ETICS), it is important to ensure that the composite structure remains intact with no breaks in the insulation layer. Tensile stress and shear strength are important in this respect.
Depending on the density, typical tensile stress values for PUR/PIR lie between 40 and 900 kPa, and shear strengths values between 120 and 450 kPa.