Quickly self-extinguishing flame retardant behavior of rigid polyurethane foams linked with phosphaphenanthrene groups

In order to explore the high-performance rigid polyurethane foams (RPUFs) with excellent flame-retardant efficiency, a reactive-type phosphaphenanthrene compound TGD was linked with RPUF matrix while the addition type flame retardants dimethyl methylphosphonate (DMMP), aluminum hydroxide (ATH) and expandable graphite (EG) were mixed into RPUF composites. The constructed flame retardant system in RPUF materials caused that a quickly self-extinguishing effect on flame were formed and the flame extinguished in just 49s during cone calorimeter test. Besides the quickly self-extinguishing effect, the flame retardant system also brought the higher limited oxygen index, the lower peak of heat release rate (pk-HRR), the less total heat release, the more residue yields. The quickly self-extinguishing effect and excellent flame retardancy of the system were caused by the continuously quenching effect from TGD and DMMP in gas phase, and by the jointly charring effect from TGD and EG/ATH, and also by the reduced fuels because TGD and other flame retardants jointly locked more carbonaceous contents in residue. The quickly self-extinguishing effect and flame retardancy from TGD/DMMP/EG/ATH system put forward a novel effective way to solve the fire-proof safety of RPUF thermal insulating materials.