Flame retardants have historically been essential ingredients in polyurethane rigid foams, particularly where a specific fire rating is required. Over the years, flame retardant usage and availability has evolved to adapt to ever-changing environmental constraints and the type of fire rating required by the industry. The flame retardant package in a polyurethane foam will have a direct impact on its burn characteristics. The flame retardant selection and the amount used are critical to a good burn performance. Good burn characteristics are essential for polyurethane foams that require a fire rating such as foam used for building wall insulation. Like flame retardants, other ingredients in the resin blend affect the burn characteristics of polyurethane foam. This includes, but is not limited to, surfactants, catalysts, polyols, and blowing agents. Proper raw material selection and quantities used in a polyurethane foam formula are keys to an excellent burn performance. In this paper, several ingredients in the resin blend of a polyurethane rigid foam will be evaluated. First, various flame retardants will be studied in polyurethane foams at three different isocyanate indexes. These foams will be evaluated for their burn characteristics with an in-house two-foot burn tunnel. This tunnel is equipped to measure flame distance and smoke evolved for an open flame burn with a constant air flow. Certain foams will also be analyzed via FTIR to determine proper cure. After an optimum flame retardant package has been selected, other ingredients, such as surfactant, catalyst, polyol, and blowing agent will be studied with the purpose of obtaining the optimum selection for burn characteristics.
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