Modified polyisocyanurates

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

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. 

Morimoto, T., Mori, T. and Enomoto, S. Ignition properties of polymers evaluated from ignition temperature and ignition limiting oxygen index. J. Appl. Polym. Sci., 22, 1911 (1978) Imai, Y. and Inukai, T. Studies on general properties of urethane-modified polyisocyanurate foams. J. Cellular Plast., 19, No. 5, 312 (1983)... 

Polyurethane-modified polyisocyanurate (PIR) foams have a reputation for being the most flame resistant of the PU related foams used for insulation. They are increasingly being made from an aromatic polyester polyol (APP) and the isocyanate is most often MDI. Unlike pol5mrethanes, however, the amount of MDI is comparatively high. Isoeyanate indices of 250 or higher are used... 

PIR foams are produced by using standard PU foaming equipment. Unmodified PIR foams have a highly crosslinked structure, and therefore are extremely brittle. What did prove successful was to lower the crosslinking density of the foams by adding modifiers, which led to, modified polyisocyanurate foams such as [40] urethane-modified PIR foam, amide-modified PIR foam, imide-modified PIR foam, carbodiimide-modified PIR foam and oxazolidone-modified PIR foam. 

Chem. Descrip. Polysiloxane-polyether copolymer surfactant Uses Foam stabilizer for rigid PU foams, continuously laminated PU boardstock, modified polyisocyanurate foams, spray foams synergistic with flame retardants Properties Cl. vise, liq. sp.gr. 1.072 0.01 g/cc vise. 730 150 mPa-s f.p. < 10 C ... 

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. 

The development of highly crosslinked rigid polyisocyanurate foams opens an excellent area of applications for polyester polyols [4-8]. The required polyols do not need high functionality and the plasticising effect of polyester structures is extremely beneficial for these highly crosslinked systems [6]. The first polyester polyols used for these applications were low viscosity polycondensation products of AA with ethyleneglycol (EG) or diethyleneglycol modified with phthalic anhydride or triols. 

Isocyanurates are usually more thermally stable than urethanes since they contain no labile hydrogen in the isocyanurate ring system. Hipchen [32a] reported the comparative thermogravimetric analysis of pure polyisocyanurate, pure urethane, and urethane-modihed polyisocyanurates. The modified isocyanurate showed a total wt loss at 300 C of 9% versus 25-30% for the urethane and 7% for the pure isocyanurate. 

Fourteen insulations were examined in this study. The insulations included three types of polyurethane, three varieties of polymethacrylimide, one polybenzimidazole, two polyisocyanurates, two polymetric isocyanate foams (one with chopped fiberglass reinforcement, one without), a modified isocyanate foam, and two insulation systems (one of polymeric isocyanate foam, one of toluenedi isocyanate foam, both with two vapor barriers and fiberglass reinforcement) ... 

---