ABSTRACT
Isocyanurate foams are commonly used as the core foam in the manufacture of continuous laminate metal-faced panels. With the impending phase out of HCFC 141b, panel manufacturers are facing the difficult decision of which alternative blowing agent to adopt. Formulators have the daunting task of providing tailored foam systems based on the alternative blowing agents which meet the processing characteristics and performance properties for this application. Since metal-faced panels are often used in construction governed by stringent combustibility standards, the flammability performance of the foam core is a major issue to be considered.
Dow Polyurethane Systems Business has been working to develop polyisocyanurate foam systems based on alternative blowing agents capable of meeting the different processing needs and performance requirements of a large customer base. Polyisocyanurate foam systems for continuous laminate metal-faced panels have been developed using the following blowing agents: HCFC 22 or cyclo/iso pentane for the U.S. market, and normal pentane for the European market. Furthermore, development is also under way for systems blown with CO2 (from the reaction water/isocyanate or gas) HFC 134a and HFC 245fa. Water, pentane, and CO2 (gas or liquid) are the most attractive alternative blowing agents from an environmental standpoint since they offer zero ODP (Ozone Depletion Potential) and zero or very marginal GWP (Global Warming Potential).
In Dow’s developmental work, foam flammability is examined using the Butler Chimney, NBS Smoke Chamber, UL 723/ASTM E-84 Tunnel, the Radiant Panel (Italian CSE / RF3), and the German DIN 4102 B-2 tests. Some metal sandwich panels are also tested according to the French M1 and the European standard draft SBI. In this paper, physical property and insulation value data are included and processing characteristics are thoroughly discussed.
