Effect of hydrogen bonding and moisture cycling on the compressive performance of poly-pyridobisimidazole (M5) fiber

摘要: A clear correlation between the degree of intermolecular hydrogen bonding (H-bonding) and axial compressive strength pyridobisimidazole (M5) as-spun fiber specimens subjected to varying annealing conditions has been established by means Fourier transform infrared microspectroscopy single elastica loop testing. As water initially contained in is removed heat treatment, improvements polymer chain orientation promote formation H-bonds, leading enhanced values. M5 with highest H-bonding 96 ± 1% are found have a 1.72 0.09 GPa. Moisture cycling experiments annealed provided direct evidence partial H-bond reversibility this material, as saturation resulted reduction from 93 64%. Upon drying at 120 °C an inert atmosphere, returned original value 93%. However, repeated moisture monotonic both saturated condition (53%) dry state (62%). The dried after was be statistically equivalent reduced level 1.29 could recovered re-annealing under tension.