Laser pyrolysis of polymers and its relation to polymer fire behaviour

Laser-pyrolysis time-of-flight mass spectrometry has been applied to the study of rapid thermal degradation of polymethylmethacrylate (PMMA) and rigid polyurethane foams. The heating rate has little influence on the mechanism of PMMA degradation. In both the laser and low heating rate experiments, monomer was the major pyrolysis product. Laser pyrolysis of rigid polyurethane foams resulted in the evolution of polypropylene glycol as the major species together with low molecular weight species such as CO2 etc. It is considered that polypropylene glycol and its further decomposed species act as fuel for the flame in a real fire situation. The ratio of polypropylene glycol to CO2 in the evolved gases decreased with the increase of isocyanate index. This is associated with the improvement of fire resistance at a high isocyanate index. (C) 1997 Elsevier Science B.V.