Rigid polyurethane and polyisocyanurate foams

Moulded high-density rigid foamed PU products (200-750 kg m ), are finding increasing use, for example in energy-absorbing blocks for car 

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The bulk of the ngid polyurethane and polyisocyanurate foam is used in insulation. See also Insulation (Thermal) More than half (60%) of the rigid foam consumed in 1994 was in the form of board or laminate die remainder was used in pour-in-place and spray foam applications. 

This book series presents in-depth reports on the most important new developments in urethane technology. Volumes 2-5 contain papers written only by Japanese specialists. A number of these papers concern rigid and flexible foams. Polyurethanes and polyisocyanurates are widely used in Japan. The papers cover recent developments in chemistry, processing, properties and applications. 

These materials not only have a good resistance to burning and flame spread but are also able to withstand service temperatures of up to 150°C. At the same time polyisocyanurate foams have the very good hydrolytic stability and low thermal conductivity associated with rigid polyurethane foams. 

BS 5608 1986 Specification for Performed Rigid Polyurethane (PUR) and Polyisocyanurate (PIR) Foam for Thermal Insulation of Pipework and Equipment, 9 pp... 

Though closed-cell rigid polyurethane foams are excellent thermal insulators, they suffer form the drawback of unsatisfactory fire resistance even in the presence of phosphorus- and halogen-based fire retardants. In this context, polyisocyanurates, which are also based on isocyanates, have shown considerable promise. Isocyanurate has greater flame resistance then urethane. Although rigid polyurethane is specified for the temperatures up to 200°F (93°C), rigid polyisocyanurate foams, often called trimer foams, withstand use temperatures to 300°F (149°C). Physical properties and insulation efficiency are similar for both types. 

In building applications rigid polyurethane foam is used laminated to board stock (or to other substrates such as foil or paper), discontinuous or continuous sandwich panels, slabstock, spray, and as pipe insulation material. Some of these sandwich structures are used in building (and transportation) applications that do not exploit their insulation characteristics. The largest volume building application is in roofing insulation [where both PUR and polyisocyanurate (PIR) foams are used]. 

Polyisocyanurate (PIR) n. A polymer containing isocyanurate rings, i.e., isocyanate trimer, and forming foams that have better fire resistance than rigid polyurethanes, but are more brittle, so are... 

The first book on the reactions of carbon cumulenes, treating the cycloaddition reactions of ketenes in depth, was written by Staudinger in 1912 Staudinger already realized that cycloaddition reactions of ketenes are common, and often ketenes were only isolated as cyclodimers. The cyclodimers of isocyanates became prominent in the development of polyurethanes in the IG Farben Laboratory in Leverkusen, Germany in the early 1930s and the cyclotrimerization of diisocyanates led to the development of polyisocyanurate foams, with thermal stability superior to rigid polyurethane foams in the 1960s. Today, polyisocyanurate foams are used in the insulation of the fuel tank of the space shuttle. Also, carbodiimide derived cellular plastics with improved thermal stability are of interest. In recent years, cumulene derived polymers became of interest as one-dimensional molecular wires. 

Czuprynski B, Paciorek-Sadowska J, Liszkowska J and Czuprynska J (2002) The utilization of rigid polyurethane-polyisocyanurate foams by the combined alcoholysis-aminolysis process, Polimery (Warsaw) 47 104-109. 

Foams are available as rigid sheets or slabs (which are used in the majority of roofing systems), as beads and granules (used in cavity wall insulation), and also as spray and pour-in applications. The market is dominated by polyurethane (PU) foams, in particular polyisocyanurate products, expanded polystyrene (PS), and extruded polystyrene. 

The possibilities for making bonded structural sandwich elements in a variety of materials are very real. However, whilst there exist structural examples such as aluminium honeycomb panels (used in aircraft and transport applications) and metal skinned foam sandwich panels (used as the monocoque chassis in refrigerated transport applications), these composite constructions are normally utilised in non- or semi-structural ways. Typical skin materials are steel, aluminium, GRP and plywood, and common core materials are rigid foam polystyrene, polyurethane, polyisocyanurate, PVC, and honeycombed aluminium. In some instances the foam core is injected between the skins and adheres to them in others, adhesives are used to bond the separate components together. The nature of the manufaeturing process depends on the type of structure to be made, and the degree of investment in produetion maehinery. Both flat and eomplex eurved forms ean be made by a hand lay-up process as well as in an automated way. 

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