No abstract

A challenge facing rigid polyurethane foam insulation today is the development of foam formulations and processing technologies that use blowing agents which are environmentally acceptable and produce foam having an excellent balance of properties. Rigid polyurethane foams are known for their outstanding combination of density, thermal resistivity, structural and fire performance, and cost-effectiveness. Such attributes are essential for, maintaining a competitive edge over alternate insulation materials. Currently, hydrocarbons and HFCs are the two leading classes of blowing agents under consideration to replace HCFCs. The benefits and challenges for each of the viable blowing agents are well known. This study focuses on hydrocarbon blown foam where the primary challenge is to meet the required regulatory firetests together with providing superior aged thermal resistance and structural performance at low densities. Learning from the ongoing commercial production with pentanes in Europe as well as from prior published works, this study systematically looks at the effects of selected polyurethane formulation and processing variables on the key polyurethane foam and laminate board performance characteristics. Formulation variables examined include pentane composition, index, and fire retardant. Processing variables examined include temperature, laydown, and the physical state of the blend. Physical properties of the laminate board and foam are discussed. ASTM E84 and Factory Mutual Calorimeter test results are presented. The results are analyzed keeping in perspective findings from years of experience with CFC-11 and HCFC-141b blown foam. Based on these evaluations, this paper outlines the key material and processing requirements for the successful use of hydrocarbon blowing agents in the North American boardstock industry.