Crystallization behavior and morphological features of two LARC polyimides and local orientation studies of two semicrystalline model composites
Muellerleile, Joan ThÃ©resÃ¨ Polesnak
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Results are presented for two unrelated studies. The primary topic involved the crystallization behavior and morphological features of two polyimides, namely LARCCPI Langley Research Center Crystalline Polymide) and LARC-TPI (Thermoplastic -Polyimide). The LARC-CPI study first considered features affecting crystallization behavior including inherent viscosity, crystallization temperature, and melt temperature and time. Data were analyzed using the Avrami analysis. Morphological features were investigated using techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and small angle x-ray scattering (SAXS). Permanganic etching combined with SEM successfully revealed morphological detail, further supported by TEM data. These data support the Avrarni analysis results. SAXS data reflected the influence of several crystallization variables on the long spacing. SAXS results also revealed the presence of a broad second scattering peak for semicrystalline samples appearing in the same position regardless of crystallization temperature or inherent viscosity. Molecular modelling predicted a low-energy helical conformation with a near-periodic repeat distance corresponding to the second SAXS peak.
- Doctoral Dissertations