Polyisocyanurate foam

Introduction. It has been recognized that CFC-ll-blown rigid urethane foams are the insulation materials with the lowest thermal conductivities, in comparison with other insulation materials, such as water-blown rigid urethane foams, glass-fiber materials, or polystyrene foams. 

Rigid urethane foams have been used exclusively in areas which require high thermal insulation and flame retardance, such as household refrigerators, deep freezers, and cold-storage warehouses. However due to the low flame retardance and poor fire resistance of rigid urethane foams, serious fire hazards have been reported and building applications 

The addition of flame retardants, either additive or reactive types, can provide flame-retardant foams having low flame spread or surface flammability, but flame retardants do not improve the temperature resistance of these foams because the thermal stability or the dissociation temperature of the urethane linkage is relatively low and unchanged by the addition of flame retardants, i.e., the linkage dissociates at about 200°C to form the original components in polyol and polyisocyanate. The dissociation can result in further decomposition of polyol and polyisocyanate into low-molecular-weight compounds at elevated temperatures. For these reasons urethane foams are not temperature-resistant nor thermally stable. 

In contrast, the isocyanurate linkage is thermally stable, as determined by TGA, as shown by a model compound study (58) and produces less combustible gases. Accordingly, unmodified isocyanurate-based polymers, e.g., resins and foams, are thermally stable, and therefore, temperature- and flame-resistant. In other words, the unmodified polyisocyanurates decompose at higher temperatures than the polyurethanes, and generate lower amounts of combustible gases than polyurethanes. 

The isocyanurate linkage is obtained by the cyclotrimerization of isocyanate groups, as shown in the following model reaction. 

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Foamed plastics (qv) were developed in Europe and the United States in the mid-to-late 1930s. In the mid-1940s, extmded foamed polystyrene (XEPS) was produced commercially, foUowed by polyurethanes and expanded (molded) polystyrene (EPS) which were manufactured from beads (1,2). In response to the requirement for more fire-resistant ceUular plastics, polyisocyanurate foams and modified urethanes containing additives were developed in the late 1960s urea—formaldehyde, phenoHc, and other foams were also used in Europe at this time. 

Roofiag panels have been made from polyisocyanurate foams, both foam- and felt-reiaforced with glass fiber. PhenoHc resias are used especially for decorative laminates for paneling. The substrate may be fiberboard or a core of expanded polystyrene beads. In one case the beads are coated with phenoHc resia, then expanded ia a mold to form a stmctural foam panel. 

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. 

The application of a glycolysis process with simultaneous deamination to the recovery of polyols from rigid PU and polyisocyanurate foam waste is described. Properties and applications of the polyols obtained are examined. GETZNER CHEMIE GMBH... 

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. 

Saiki, K. Sasaki, K. Carbodiimide-modified polyisocyanurate foams Preparation and flame resistance. 

Fallon, S. Roark, R. Novel flame retardants for hydrocarbon blown polyisocyanurate foams. Book of Abstracts, Polyurethanes Expo, Orlando, September 30-October 3, 2003 American Plastics Council Washington, pp. 42M-6. 

Modesti, M. Simioni, F Checchin, M. Pielichowski, J. Prociak, A. Thermal stability and fire performance of modified polyisocyanurate foams. Cell. Polym. 1999, 18, 329-342. 

Feske, E.F. Brown, W.R. Flame retardant pentane blown polyisocyanurate foams for roofing. Book of Abstracts, Proceedings of Polyurethanes Expo 2002, Salt Lake City, UT, October 13-16, 2002 American Plastics Council Washington, 2002 pp. 32-40. 

Polyisocyanurate foams, polyurea foams and phenolic foams are growing rapidly in recent years. Urea-formaldehyde foams disappeared recently from the U.S. market. Rubber foams and pyranyl foams are no longer available in the worldwide market. 

Physical blowing agents may be classified as CFCs (chlorofluoro-carbons), HCFCs (hydrochlorofluorocarbons), HFCs (hydrofluorocarbon ethers) and non-fluorine-containing organic liquids. These fluorinated blowing agents can also be used in foaming polyisocyanurate foams, polyoxazolidone foams, and polyurea foams. 

Ashida, K., "Polyisocyanurate Foams" in Handbook of Polymeric Foams and Foam Technology, eds., Klemimer, D., and Frisch, K.C., Hanser, New York (1992). 

AX-106 Polyurethane and Polyisocyanurate Foam Insulation (Sweets Brochure). 

AX-119 Guide for the Safe Handling And Use of Polyurethane and Polyisocyanurate Foam Systems (U-118). 

Covers both polyurethane and polyisocyanurate foam, board or block, for use from -55 to 70 C (-65 to 160 F). Application is primarily for sandwich construction. 

Glass-fiber incorporation increases the fire resistance of polyisocyanurate foam laminates. The glass fibers embedded in the foam prevent the development of deep fissures in the protective carbonaceous char that is formed when polyisocyanurate foam is exposed to high temperature flames. ... 

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