SYNTHESIS, THERMAL-PROPERTIES, AND FLAME RETARDANCY OF PHOSPHORUS-CONTAINING POLYIMIDES

Phosphorus containing polyimides were prepared via phosphorylation of organosoluble polyimides. This was achieved by phenoxaphosphine oxide ring formation reaction or esterification with diethylchlorophosphate. The phosphorylation was confirmed by infrared, P-31 nuclear magnetic resonance, and elemental analysis for phosphorus. Polyimides containin g phosphorus of 8.3 and 5.4% by weight were found. Thermal characteris tics and decomposition behavior of the resulting polyimides were inves tigated by differential scanning calorimetry and thermogravimetric ana lysis. Introduction of phosphorus into polyimides slightly reduced the ir initial weight loss temperatures and led to high char yields at tem peratures higher than 800 degrees C. Limiting oxygen index values high er than 48 were found for the phosphorylated polyimides. Such properti es make these polymers useful in flame retardant applications. (C) 199 7 John Wiley & Sons, Inc.