Rules governing high temperature stabilization of polyheteroarylenes

It was shown that the addition of various compounds containing phosphorus slows down thermal oxidative degradation of polyimides, polybenzoxazoles and their model compounds, reduces the gravimetric loss of samples and the separation of volatile breakdown products. The amount of gel fraction formed during oxidation of stabilized polymers is higher than that formed during oxidation of unstabilized samples, which is evidence of the formation of a three dimensional structure in the polymer, more stable under conditions of thermal oxidation. During oxidation of stabilized polybenzoxazole practically the entire phosphorus remains in the solid polymer residue after breakdown. Some parameters of the three dimensional structure of polybenzoxazoles and polyimides were calculated from the ratio of gel and sol fractions using the Charlesby theory. A study was made of the reactivity of stabilizers containing phosphorus in relation to peroxide radical of model compounds.