Polyimide Fibers Obtained by Spinning Lyotropic Solutions of Rigid-Rod Aromatic Poly(amic ethyl ester)s
✍ Scribed by Christian Neuber; Hans-Werner Schmidt; Reiner Giesa
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 424 KB
- Volume
- 291
- Category
- Article
- ISSN
- 1438-7492
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✦ Synopsis
Abstract
Summary: Fibers were spun from a lyotropic solution of a high‐molecular‐weight (η = 5.89 g · dL^−1^), rigid‐rod, fully aromatic polyimide precursor polymer in a dry‐jet, wet‐spinning process in NMP. Acetone was identified as the coagulant of choice since fibers could be drawn extensively in this solvent, resulting in improved mechanical properties (tensile modulus: E = 17 GPa, strength at break: σ~break~ = 400 MPa, elongation at break: ε~break~ = 5.3%) and orientation, which was shown by WAXS patterns. SEM images showed a layered, skin‐core morphology without any visible fibrillation. Additional processing of these fibers by step‐wise hot‐drawing up to 400 °C under tension rendered oriented polyimide fibers with excellent mechanical properties. (E = 68 GPa, σ~break~ = 700 MPa, ε~break~ = 1%). An analysis of the WAXS diffraction patterns showed an improved orientation of the fibers in the axial and lateral directions; however, probably due to the CF~3~ side groups, the lateral distance was still too large for crystallization. SEM images of these imidized fibers showed, for the first time, a fibrillar morphology in addition to the typical, skin‐core, sheet‐like morphology.
SEM image of the hot‐drawn fiber PI 4 (12). The image shows a skin‐core morphology which was delaminating into ribbons during preparation.
magnified imageSEM image of the hot‐drawn fiber PI 4 (12). The image shows a skin‐core morphology which was delaminating into ribbons during preparation.