Effect of Heat Treatment on Properties and Structural changes of Poly(p-phenylene benzobisoxazole) Fiber

The changes of structure and mechanical properties of poly(p-phenylene benzobisoxazole) (PBO) fibers with different heat-treatment condition involving temperature, level of tension and duration was investigated. The results revealed that the modulus of fibers was affected greatly by the heat treatment, while the strength of fiber was insensitive to the applied parameter during the heat treatment. It was also found that the heat treatment could promote the ring-close reaction of PBO molecules to completion and impelled the molecular chains to adjust and slide along the stress direction for further orientation, which could make the molecular chain more stretched, regularize the structure of PBO fibers and improve the mechanical properties of PBO fiber.