Imide-modified isocyanurate

Imide-Modified Isocyanurate Foams. The imide linkage is a thermally stable linkage, and therefore, imide-modified isocyanurate foams have higher thermal stability and flame retardance than urethane-modified isocyanurate foams. R. Grieve (114) prepared such foams in a one-shot process by reacting a polycarboxylic acid anhydride with an organic polyisocyanate in the presence of a catalytic amount of a monomeric homocyclic polyepoxide and a tertiary amine. 

Modification of cellular polymers by incorporating amide, imide, oxa2ohdinone, or carbodiimide groups has been attempted but only the urethane-modified isocyanurate foams are produced in the 1990s. PUIR foams often do not require added fire retardants to meet most regulatory requirements (34). A typical PUIR foam formulation is shown in Table 6. 

The modification linkages include urethane, amide, imide, carbodiimide and oxazolidone linkages. A urethane-modified isocyanurate foam (trade name Airlite Foam SNB, Nisshinbo, Ind. Inc.) was first applied to the petrochemical industry as a seamless fire-resistant insulant in 1965 (39). 

Modified polyisocyanates are prepared by incorporating at least one linkage into monomeric polyisocyanates. Such linkages include urethane, carbodiimide, allophanate, biuret, amide, imide, isocyanurate, and oxazolidone. These modifications provide some advantages, e.g., lower vapor pressure, increased viscosity, and controlled reactivity. 

In the same period it was found that using tris-(2-hydroxyethyl)-isocyanurate (THEIC) for polymer branching increases the cut through of the polyester film substantially [7]. The poly(ester-imide)s were modified with THEIC, and improved materials were obtained (Fig. 1) [8]. 

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