Thermal stability of flexible polyurethane foams obtained from reactive phosphorus-containing polyols dispersed in polyethylene glycol

Flame-retardant and flexibility-enhanced phosphorus-polyurethane foams (P-PUF)s were prepared from phosphorus–hydroxyl precursors and polyethylene glycol (PEG) as polyols. In the first step, three different precursors, such as tris-(5-hydroxypentyl) phosphate (P-Pen-OHs), tris-(4-hydroxybutyl) phosphate (P-But-OHs), and tris-(3-hydroxypropyl) phosphate (P-Pro-OHs) were synthesized and used as flame retardants. In the second step, the precursors were made to react with toluene-2,4-diisocyanate to modify the flexibility and flame retardancy properties of the P-PUF product. The P-PUFs were obtained by a one-shot process system and then analyzed for their thermal stability, flame retardancy, and compressive strength properties. Among all P-PUF samples, P-But-PUF showed the best compressive properties with a Young’s modulus value of 0.167 MPa. The compressive properties of P-PUF are found to be proportional to their relative density. These results show that the chemical structure of the phosphorus–hydroxyl precursor had a slight effect on the compressive properties as well as the porosity of the final materials. All the foams had T_g values in the range of 58–70 ℃ and their thermal degradation in a nitrogen atmosphere started around 100 ℃. From the limiting oxygen index test, P-PUF samples are considered marginally stable materials with a slow-burning behavior that confirms the efficiency of reactive phosphorus-based flame retardants.

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