Polyurethane (PU) rigid foam is one of the most efficient, high performance insulation materials. It provides desirable properties such as low thermal conductivity, low density, excellent dimensional stability, fire resistance, low moisture permeability and water absorption and durability. Fire resistance is one the most important properties of these materials because building codes require building materials to meet applicable fire safety standards. Flame retardants play an important role in PU rigid foam system. One of most common flame retardants used in PU rigid foams is tris (2-chloroisopropyl) phosphate (TCPP). Often times it is used with the combination of reactive brominated flame retardants (Saytex RB-79) because phosphorus and bromine based flame retardants are synergistic. The reactive brominated flame retardants can get incorporated into the PU backbone, whereas TCPP is not reactive, and has the potential to migrate out of the foam, and over years the flame resistance will go away. In our recent study, a sulfur-containing aromatic diamine (Ethacure 300) has been used with the combination of reactive brominated flame retardants in PU rigid foams. It is very interesting to note that there is a significant flame retardant synergistic effect between sulfur (Ethacure 300) and bromine (Saytex RB-79). The presence of nanoclay in the FR package can further enhance the flame resistance performance. The rigid foams also demonstrated excellent compressive strength, and high dimensional stability and R value of 7. This study indicated benefits associated with development of flame retardant compounds that are fully reactive and compatible with the foam manufacturing process as they help achieve ASTM E84 class A while maintaining other important properties such as high R value, high dimensional stability and good compressive strength.
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