Relevant factors in scorch generation in fire retardant flexibile polyurethane foams. 2: Reactivity of isocyanate, urea and uretane groups

Water blown polyurethane foams contain an essential amount of amino groups, urea and urethane bridges as well as residual isocyanates. In order to understand the appearance of scorch in some flame retardant polyurethane systems, the reactivity of isocyanates, urea and urethane bridges with flame retardants has been investigated using model compounds. Both IR and UV analyses showed the lack of chemical interaction of isocyanates, ureas and urethanes with aromatic phosphates, brominated diphenylethers, halogenated-aliphatic and aliphatic phosphates at the temperature and in the timescale of a typical foaming process. Only a physical interaction between these groups and the fire retardant which involved disruption of the H bonding network in the original systems was observed. The ability of the flame retardant to break the hydrogen bonds was controlled by the viscosity of flame retardant. It was concluded that the scorching is not linked to the reactions with urea, urethane or isocyanate groups.