STABILITY AND DEGRADATION OF POLY(NAPHTHOYLENEIMIDOBENZIMIDAZOLE)

It has been shown that the changes with time of the mechanical charact eristics of films and fibres of poly(naphthoyleneimidobenzimidazole) ( PNIB) under atmospheric conditions at room temperature are accompanied by slow degradation of the macromolecules. This is indicated by a dro p in intrinsic viscosity, an increase in translational diffusion of th e macromolecules and a decrease in characteristic orientation of how b irefringence (FB) in PNIB solution in concentrated H2SO4. The decrease in molecular (M) is considerably accelerated for PMIB in the powdered state. Resynthesis (heating under vacuum at 250 degrees C) partially restores M of the sample. However, both resynthesized and precipitated (into water) PNIB samples retain a tendency to self-degradation.