Environmental effects on poly‐p‐phenylenebenzobisoxazole fibers. II. Attempts at stabilization

Approaches to alleviate the environmental degradation of as‐spun poly‐p‐phenylenebenzobisoxazole (PBO AS) fibers by moisture, acidic conditions, and UV–visible radiation were implemented and tested for efficacy. The general approaches tested include: extraction and neutralization of residual phosphoric acid using supercritical carbon dioxide; the use of UV–visible light blocking coatings of exfoliated graphite, carbon black, and glassy titanium dioxide; and improvement of initial fiber properties by the application of forces tending to compact the fiber microstructure.