Slabstock rigid foam is called bun foam or block foam. The essential raw materials for making block foam are isocyanate, polyol, catalyst, surfactant, and blowing agent. Block rigid foam is produced by a continuous or discontinuous process. Foam sizes are chosen based on applications. An example of foam sizes is 1.0 m wide × 0.5 m high × 4 m long. The block foam is used by cutting for different applications such as core foam of sandwich panels and pipe covers. As a blowing agent (BLA) can be used physical blowing agents. An example of BLA are the use of HCFCs, cyclopentane and etc. in formulated polyols for improving the resulting foam. Another important effect of adding physical blowing agents to the formulation is to reduce the rate and amount of heat buildup in block rigid foams. In order to prevent foam shrinkage, foam densities should be increased to resist to the atmospheric pressure; the necessary density is at least 45 k/m3.
