Why polyurethane is an excellent insulant
- Low thermal conductivity
Rigid polyurethane foam has one of the lowest thermal conductivity ratings of any insulant, which allows efficient retention of heat or, alternatively, maintenance of a refrigerated or frozen environment.
Effective insulation in all types of buildings plays a vital role in the conservation of non-renewable fossil fuels, which reduces emissions of carbon dioxide gas released by the burning of fuels for energy and therefore reduces global warming.
Rigid polyurethane foam provides a high level of compression and shear strength, which is further enhanced by bonding with facing materials such as metal or plasterboard.
Rigid polyurethane foam can be made either under continuous block or batch factory production, or by on-site mixing for spray and injection purposes.
During the short period between mixing and final curing, rigid polyurethane foam is extremely adhesive, which allows it to bond effectively with a wide range of building facings. The adhesion is so strong that the bond strength is usually higher than the tensile or shear strength of the foam.
Rigid polyurethane foam is compatible with a large number of building facings, including paper, foil, glass fibre, aluminium, plasterboard, plywood and bitumen. These can complement the inherent strengths of the foam, enabling use as semi-structural panels and cladding and allowing foam to accept cosmetic finishes such as plaster to operate effectively as moisture barriers in conditions of high humidity.
- In-situ stability
Rigid polyurethane foam can be used in applications which experience exceptional extremes of temperature, from -200 deg. C to +100 deg. C.
- Water absorption
The water vapor permeability of rigid polyurethane foam is low and is enhanced in most building applications by the incorporation of a moisture barrier of polyethylene film or aluminium foil.
- Fire properties
Like all organic building materials - wood, paper, plastics, paints - rigid polyurethane foam is combustible, although its ignitability and rate of burning can be modified to suit a variety of building applications and it can be formulated to meet the relevant national regulations.
Rigid polyurethane foams are usually used at lower thicknesses than other insulants, which means that their heat or fuel contribution to a fire is low compared to other, thicker insulating materials. The overall fire performance of an insulation panel can be significantly enhanced by the material that is used to face the panel - for example, steel.
Independently monitored, large-scale tests of buildings incorporating rigid polyurethane and polyisocyanurate (PIR) foam insulation carried out in the USA and Europe have concluded that, properly used, these materials do not add to the severity or serious hazard of fires.
At low densities (e.g. 30kg/m3), the volume of polyurethane polymer in rigid polyurethane foam is around 3 per cent. The remaining 97 per cent of the foam is gas trapped within the cells, which provides the low thermal conductivity properties.
The lightness of the foam is an important aspect in terms of transportation, handling and ease of installation.
- Chemical resistance
Rigid polyurethane foam provides excellent resistance to a wide range of chemicals, solvents and oils.