Evaluation Of The Alkali And Oxidation Resistance Of Pbo Fibers

Poly(p-phenylene benzobisoxazole) (PBO) fiber, well-known for its super high strength, is a novel fiber with excellent heat resistance and flame retardancy. However, chemical stability appears to be one of its few weaknesses. In this study, PBO fibers were treated with sodium hydroxide (NaOH) and potassium permanganate (KMnO4) solutions under various conditions. Scanning electron microscopy, optical microscopy, tensile testing, Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis were employed to characterize the variations of its structure and properties. The results show that many longitudinal corrosion grooves appeared on the surface of PBO fibers treated with KMnO4, while only subtle microcracks occurred after treatment with NaOH. The breaking tenacity of the fiber decreased from 38.13 cN dtex(-1)to 2.76 cN dtex(-1)after treatment with KMnO(4)for 6 h, while it remained at a higher level (27.67cN dtex(-1)) when treated with NaOH. After treatment with KMnO(4)solution, a more obvious absorption peak appeared in the vicinity of 1448.3 cm(-1), inferring an occurrence of chemical changes for oxazole ring. Moreover, the remaining mass and initial degradation temperature are significantly improved, also indicating that the cyclic or cross-linked structure is rebuilt. Furthermore, the cyclization or cross-linking of macromolecules destroyed the highly ordered structure of PBO fibers, demonstrated by acromion melting peaks at low temperature in the DSC curves. However, the aggregation and chemical structures of PBO fibers have no obvious changes after treatment with NaOH.