Dynamic mechanical properties of N‐phenylnadimide modified PMR polyimide composites

Temperature‐frequency dependence of α, β, and γ transitions was determined using a Rheometrics dynamic spectrometer on a series of unidirectional Celion 6000/N‐phenylnadimide (PN) modified PMR polyimide composites. The objective was to see if any correlations exist between crosslinked network structure and dynamic mechanical properties. Variation in crosslinked network structures was achieved by altering the polyimide formulation through addition of various quantities of PN into the standard PMR‐15 composition. As a control, PMR‐15 composite system exhibited well‐defined α, β, and γ transitions in the regions of 360, 100, and −120°C, respectively. Their activation energies were estimated to be 232, 60, and 14 kcal/mole, respectively. Increasing the amount of PN concentration caused (a) lowering of the activation energies of the three relaxations, (b) a decrease of the glass transition temperature, and (c) increasing intensities of the three damping peaks, compared to the control PMR‐15 counterpart. These dynamic mechanical responses were in agreement with formation of a more flexible co‐polymer from PN and PMR‐15 prepolymer.