Rheological and Spectroscopic Characterizations of the Properties of a Prepolymer for High-Temperature Applications: The IP960 System

Abstract

Of the thermostable polymers on the market the American PMR-15 resin is a reference compound. Nevertheless, its defects have necessitated the development of new polymers such as IP960. The object of this work is to characterize IP960 which is soluble in the diglyme until the imide oligomer stage. HPLC and 1H NMR analyses of the prepolymer demonstrate its polymolecularity. Several isomer forms, due to possible conformations of the nadimide endcaps, are present in equal amounts in the medium. The combined use of differential scanning calorimetry and rheological techniques have allowed us to study and to explain the evolution of properties of the prepolymer with temperature (glass transition, crosslinking etc). Using FTIR spectroscopy, we have studied the structure of the polymer network. Our results seem to confirm the validity of the crosslinking diagram of nadic structures proposed by Wong and co-workers. Thermomechanical analysis of the crosslinked compound shows that the Tg of the polymer is close to 292 °C. It also reveals on the curb of the modulus G″, namely the presence of two peaks γ and β associated with secondary mechanical relaxations within macromolecular chains ( Tγ = −102 °C; Tβ =68 °C).