A reactive flame retardant containing appox. 73%aliphatic bromine. It combines a high bromine content with exceptional stability and is particularly suitable where thermal. hydrolytic and light stability are required. Major uses of it are as a reactive intermediate for high molecular weight flame retardants, particularly in combination with phosphorus. and as a reactive flame retardant for polyurethanes where its high solubi1ity in the system makes it especially useful. It reacts through its single hydroxyl function to form pendant urethane groups. Its high bromine content and good compatibility in CFC-free PU systems enables high standards of fire retardancy to be reached together with good foam properties in both rigid and flexible PU. Effective combination of properties may be achieved by use of mixtures of it which is monofunctional and FR-522(DBNPG) which is difunctional.