fire behavior of rigid polyurethane foam and metal faced polyurethane sandwich panels and its fire hazard assessment

reaction to fire of fire-retarded rigid pur foams and two types of metal faced rigid polyurethane foam core sandwich panel was evaluated by using cone calorimeter test method. the tests were carried out in various radiative heat fluxes from 15 to 75 kw/m2. the radiation rate effect on reaction to fire parameters, including time to ignition (tti), peak of heat release rate (prhr), total heat release (thr), average heat release rate (av.rhr) and average heat of combustion (av.ehc) was investigated. the phenomenon of char forming, when the foam is exposed to heat, leads to the formation of a protective layer on the surface of foam and hence no direct relation exists between av.rhr and average specific mass loss rate (av.spec.mlr) of foam with increased radiation rate. in addition, the increased prhr with foam density was also very smooth. the relation between tti and heat flux was investigated for the foam and its corresponding correlation has been achieved with a specified density. fire hazard assessment of foams and sandwitch panels was carried out by adopting petrella and richardson fire risk classification methods. the assessment results showed that rigid pur foam and pur sandwich panels may have a high contribution to bring the room to critical flashover condition, but the risk is intermediate from the viewpoint of fire endurance. the reasons of these risk levels are attributed to a very short tti, relative high prhr and an intermediate amount of thr. decrease in foam density reduces heat release but it shows no significant effect on reducing flashover hazard.