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Polyimide Fibers Obtained by Spinning Lyotropic Solutions of Rigid‐Rod Aromatic Poly(amic ethyl ester)s
Author(s) -
Neuber Christian,
Schmidt HansWerner,
Giesa Reiner
Publication year - 2006
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/mame.200600256
Subject(s) - materials science , polyimide , composite material , spinning , morphology (biology) , ultimate tensile strength , fiber , crystallization , core (optical fiber) , modulus , lyotropic , lamellar structure , polymer , chemical engineering , liquid crystalline , layer (electronics) , genetics , engineering , biology
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.