Polyurethane Product description
Polyurethane (PUR) plastics were developed originally in the 1930s and were used primarily in military and aerospace applications until the 1950s. Their application in consumer and industrial products became popular in the late 1950s, when they were used mostly for cushioning (flexible foam), coatings (polyurethane modified oil-based), and thermal insulation applications (rigid foam). In the 1970s, there was a growth in the use of rigid PUR foam thermal insulation in refrigerators, as panel products, and in spray – applied insulating foam. Development of new chemical recipes and catalysts in Europe and the United States resulted in a next-generation product called polyisocyanurate foam (PIR). Also called polyiso foam, it first appeared on the U. S. market in the mid-1970s.
PUR and PIR insulations are manufactured by chemical reactions between polyalcohols and isocyanates. Both are a closed-cell board product in which the cells contain refrigerant gases instead of air. The boards are usually double-faced with foil or sometimes come bonded with an interior or exterior finishing material. The boards must be protected from prolonged exposure to water and sunlight, and if used in an interior application, they must be covered with a fire-resistant thermal barrier material such as gypsum wallboard.
Thermal drift is an issue with each of these foams. Over the first few years after installation, the R-value of the foam drops as the gas slowly escapes from the cells and is replaced by ambient air. Experimental data on polyurethane foams indicate that most thermal drift occurs within the first 2 years after manufacture. Foil and polymer sheet facers on foam boards can inhibit the escape of gas from the cell structure. Laboratory and field testing data suggest that the stabilized R-value of rigid foam with metal foil facers remains unchanged after 10 years, usually 7.1 to 8.7 per inch.9
Rigid PUR and PIR foams will, when ignited, burn rapidly and produce intense heat and dense smoke and gases that are irritating, flammable, and/or toxic. As with other organic materials, the most significant gas is usually carbon monoxide. Thermal decomposition products from PUR foam consist mainly of carbon monoxide, benzene, toluene, oxides of nitrogen, hydrogen cyanide, acetaldehyde, acetone, propene, carbon dioxide, alkenes, and water vapor.1