Flame Retardant Polyols

A special group of polyols for rigid PU foams is the group of reactive flame retardant polyols containing phosphorus, chlorine or bromine, which confer fire resistance to the resulting PU (Chapter 18). 

These polyols called flame retardant polyols, have terminal hydroxyl groups, react with polyisocyanates in the process of PU synthesis and are chemically inserted in the PU structure. The reactive flame retardants being chemically linked in the PU chains assure a permanency of flame retardancy [5, 6, 11]. 

Zhang L, Zhang M, Hu L, Zhou Y. Synthesis of rigid polyurethane foams with castor oil-based flame retardant polyols. Ind Crop Prod 2014 52 380-388. 

Blending of sugar-based polyols with flame retardant polyols or additives also is quite common. Certain flame retardant additives such as tris-(chloro-ethyl) phosphate also serve as a viscosity reducing agent although the addition of greater cunounts of this phosphate may affect adversely certain foam properties, e.g. humid aging characteristics. 

Polyether polyols for rigid urethane foams currently are (August, 1976) priced at 37 - 45 cents/pound while special, flame-retardant polyols command premium prices... 

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