Synthesis Of Reactive Phosphorous Flame Retardant And Its Application In Rigid Polyurethane Foam

In this paper, the phosphaphenanthrene flame retardant DOPO was selected, together with maleic acid, EG and GL, to synthesize three novel flame retardant polyols: DOPO-MA-EG. DOPO-MA-VG+EG?and DOPO-MA-VG via nucleophilic addition and plyesterification reactions. The basic physico-chenical parameters of these polyols were examined by their acid values, hydroxyl values and colours; the structures and other properties of these polyols were characterized by FTIR,1HNMR, and GPC methods. The characterization also proved the polyols structure with ?-hydroxyl and DOPO functional groups in these synthesized compounds. And with the addition of glycerin, the activity of hydroxyl groups in these flame retardant polyols reduced, their acid values increased slightly, their hydroxyl values and weight average molecular weight increased. Their thermal performances of were studied by DSC, and TGA, and the results showed that these polyols have high thermal stabilityies and excellent char-forming abilities.Secondly, the DOPO-MA-EG, DOPO-MA-VG+EG polyols was selected to prepare the phosphorus-containing halogen-free rigid polyurethane foams as the reactive flame retardants. The effect of phosphorus contents to the flame retardant and mechanical properties of these rigid polyurethane foam was studied. The experiment results showed that with more phosphorus-containing polyols addition, the size of gas pores in these rigid polyurethane foams was reduced, their compression resistant strength increased; their charcoal-forming temperatures increased significantly, their char residue after burning increased significantly under 800?. These facts indicated that the increasing of the phosphorus content could greatly increase the flame retardant performance of the rigid polyurethane foam products. With 1.5% phosphorus content these rigid polyurethane foam showed the oxygen index higher than 26, which meets the requirement of UL-94Vo standardFinally, based on the elemental and structural effects on the flame retardant, the expandable graphite was added into these PIR rigid foams to prepare three different kinds of PIR rigid foam flame retardants with synergistic effect. The effect of the expandable graphite contents to the flame retardant and mechanical properties of these rigid polyurethane foams was studied. The results showed that the addition of the expandable graphite have positive synergistic flame resistant effcet with the synthesized DOPO-based RPUF. When the phosphorus content was 1.5% and the expandable graphite content was 12.5%, the product got the best flame retardant ability:its LOI index was over 30 and met the B1 combustion class of national standard. The mechanical properties of these RPUF products also improved when the content of the expandable graphite increased within some certain amount, but decreased greatly when excessive expandable graphite was added. This may due to the reunite of the polyurethane caused by the excess expandable graphite, which could lower the compatibility of the componts and damaged the rigid foam structure.