Effects of light stabilizer on the ultraviolet stability of poly-p-phenylenebenzobisoxazole (PBO) fibers

Abstract

A UV-resistant PBO fiber containing light stabilizer OB-1(2,2′-(1,2-ethenediyldi-4,1-phenylene) bis-benzoxazole) is reported. OB-1/PBO Fiber, which had excellent mechanical properties as PBO was prepared via in situ polymerization and dry-jet wet-spinning technique. Effects of the light stabilizer (OB-1) on UV stability of PBO fiber and possible degradation mechanism were investigated by tensile testing, intrinsic viscosity measurement, SEM, and ATR-FTIR analysis. Under UV-accelerated aging, the tensile strength of PBO fiber declined sharply. After exposed to UV 340-nm light for 310 h, the strength retention was only 44.17 %. SEM analysis showed the smooth and compact surface with well-oriented microfibrils was damaged. Meanwhile, the photostability of PBO fiber could be enhanced greatly by adding a small amount (0.05–0.2 %) of OB-1. Under the same conditions, the strength retention of 0.2 %OB-1/PBO fiber increased to 64.84 %, which was 47 % higher than that of PBO fiber. SEM observation showed the surface of OB-1/PBO fiber was also damaged, but it was not as so severe as PBO fiber. After UV irradiation, the intrinsic viscosity of PBO and OB-1/PBO fiber decreased which implies that mild chain scissions occurred. ATR-FTIR analysis revealed that oxazole rings in PBO and OB-1/PBO backbone were disrupted and formed amide linkages. These results indicated the loss of strength is mainly due to the break of microfibrils and fiber morphology, mild chain scission, and the disruption of oxazole rings.