Insulation materials, thermal rigid polyurethane foam

Nieuwenhuyse, E. (2006) Thermal Insulation Materials Made of Rigid Polyurethane Foam, Report No. 1, Brussels, Belgium Foundation of European Rigid Polyurethane Foam Associations. 

Plastics — rigid polyurethane foam, expanded polyst3u-ene, honeycomb, crosslinked PVC foam (one of the most important core materials), poljnnethacrylimides, other plastics foams (excellent thermal insulation, weaker and more expensive than paper). 

The application of microwave irradiation is expected to help in the preparation of environmentally benign renewable components for polyurethane foams.The vegetable oil-based polyols are examples of such components that can be used to obtain rigid polyurethane foams that possess satisfied properties for use as thermal insulating materials. 

Rigid foams can be processed as continuous panels or by lamination between two surfacing materials (sandwich panels with a rigid polyurethane foam core). Composite sandwich panels may have particleboard or plasterboard on one surface and cement on the other. Foams can also be produced to fill cavities between metal sheets or sheets of reinforced plastics or in combination on either side. These structures are used as thermal insulation for refrigerator and freezer cabinets, refrigerated transportation vehicles, water heaters, pipes, pipe shells, tanks for gas storage or transport of liquified natural gas, and so on. 

Thermal degradation of foams is not different from that of the solid polymer, except in that the foam structure imparts superior thermal insulation properties, so that the decomposition of the foam will be slower than that of the solid polymer. Almost every plastic can be produced with a foam structure, but only a few are commercially significant. Of these flexible and rigid polyurethane (PU) foams, those which have urethane links in the polymer chain are the most important. The thermal decomposition products of PU will depend on its composition that can be chemically complex due to the wide range of starting materials and combinations, which can be used to produce them and their required properties. Basically, these involve the reaction between isocyanates, such as toluene 2,4- and 2,6-diisocyanate (TDI) or diphenylmethane 4,3-diisocyanate (MDI), and polyols. If the requirement is for greater heat stability and reduced brittleness, then MDI is favored over TDI. 

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