Rheological Study of a High-Performance Polyimide. Interpretation of the Secondary Mechanical Relaxations of a Nadimide Crosslinked System

Thanks to the study of model compounds, we have been able to determine the origin of three rheological transitions observed in the thermomechanical analysis of a crosslinked nadimide resin, in the thermal range (-150 °C–-400 °C). The first one, localized at about 300 °C, is attributable to the glass transition of the crosslinked compound. The two others (called γ and β) are respectively situated at -100 °C and 70 °C. They are due to localized motions of rigid segments comprising aromatic structures and imide rings.