Diphase flame-retardant effect of ammonium polyphosphate and dimethyl methyl phosphonate on polyisocyanurate-polyurethane foam

Building energy consumption is an important component in the total social energy consumption. How to reduce building energy consumption became an important issue in today's society. Therefore, building insulation materials, as a kind of effective energy saving method, has been widely used for the external walls. However, the occurrence of many building fires caused by the ignition of the flammable insulation materials has brought serious damage to people. Consequently, it is significant to develop insulation materials which possess high level of fire safety. The aim of this study was to develop high efficient phosphorus-based flame-retardant system for polyisocyanurate-polyurethane (PIR-PUR) foam. Ammonium polyphosphate (APP) was used as condensed phase flame retardant and dimethyl methylphosphonate (DMMP) were used as gas phase flame retardant for preparing flame-retardant PIR-PUR foam. The flame retardancy, thermal decomposition, and combustion behaviors of PIR-PUR foams were evaluated by limiting oxygen index (LOI) test, vertical burning test, thermogravimetric analysis, cone calorimeter test (Cone), and microscale combustion calorimeter test, respectively. The LOI results showed that the PIR-PUR sample simultaneously containing APP and DMMP possessed higher flame retardant efficiency, which indicated that APP and DMMP possessed synergistic flame-retardant effect in PIR-PUR foam. Cone results indicated that the presence of DMMP can delay the ignition of specimen and delay the time to reach the maximal peak heat release rate. Moreover, the mechanical performance and thermal insulating properties were evaluated, respectively.