Structure and properties of melt-extruded LaRC-IA (3,4 '-ODA 4,4 '-ODPA) polyimide fibers

LaRC-IA polyimide fibers were extruded from the melt and drawn. The fibers were characterized by sonic pulse propagation, polarized optical microscopy , calorimetric analysis, X-ray diffraction, and tensile testing. When the a morphous, essentially isotropic, as-extruded filaments were heated slowly i n a calorimeter, no "cold" crystallization could be detected. However, when these filaments were drawn at temperatures above the T-g of the polymer, t hey crystallized rapidly to produce oriented semicrystalline structures. Th e consequent increases in modulus and strength were significant, with the p roperties reaching the levels of commercial fibers of intermediate tenacity . (C) 1999 Jokn Wiley & Sons, Inc.