The dynamic relaxation characteristics of Matrimid® (BTDA-DAPI) polyimide have been investigated using dynamic mechanical and dielectric methods. Matrimid exhibits three motional processes with increasing temperature: two sub-glass relaxations (γ and β transitions), and the glass-rubber (α) transition. The low-temperature γ transition is purely non-cooperative, and displays an identical time-temperature response to both the dynamic mechanical and the dielectric probes with a corresponding activation energy, EA = 43 kJ/mol. The β sub-glass transition shows a more cooperative character as assessed via the Starkweather method. Comparison of dynamic mechanical and dielectric data for the β process suggests that the dynamic mechanical test (EA = 156 kJ/mol) is sensitive to a broader, more strongly correlated range of sub-glass motions as compared to the dielectric probe (EA = 99 kJ/mol). Time-temperature superposition was used to establish mechanical master curves across the glass-rubber (α) relaxation, and these data could be described using the Kohlrausch-Williams-Watts function with an exponent value, βKWW = 0.34. The corresponding shift factors were used as the basis of a cooperativity plot for the determination of dynamic fragility. The relation between fragility index (m = 115) and βKWW for the Matrimid polyimide was in good agreement with the wide correlation reported in the literature.
|Number of pages||7|
|State||Published - Jan 28 2009|
Bibliographical noteFunding Information:
Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund (PRF #45353-AC7) for partial support of research activities conducted at the University of Kentucky. In addition, we are pleased to acknowledge the assistance of Dr. Matthew Weisenberger of the University of Kentucky Center for Applied Energy Research in the performance of the dynamic mechanical measurements. Research activities at the University of Texas at Austin were supported by the National Science Foundation (Grant DMR-0238979 administered by the Division of Materials Research-Polymers Program) and by Air Liquide/Medal.
- Dielectric spectroscopy
- Dynamic mechanical analysis
- Physical aging
ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Materials Chemistry