In recent years, poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers have become prominent in high strength applications such as body armor, ropes and cables, and recreational equipment. The objectives of this study were to expose woven PBO body armor panels to elevated temperature and moisture, and analyze the chemical, morphological and mechanical changes in PBO yarns extracted from the panels. A 30 % decrease in yarn tensile strength, which could be correlated to changes in the infrared peak absorbance of key functional groups in the PBO structure, were observed during the 26 week elevated temperature/elevated moisture aging period. Substantial changes in chemical structure were observed via infrared spectroscopy, as well as changes in polymer morphology observed using microscopy and neutron scattering. When the panels were removed to an ultra-dry environment for storage for 47 weeks, no further decreases in tensile strength degradation were observed. In a parallel study, fibers were sealed in argon-filled glass tubes and exposed to elevated temperature; less than a 4 % decrease in strength was observed after 30 weeks.
Citation: NIST Interagency/Internal Report (NISTIR) - 7373
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
ATR, attenuated total reflectance (ATR), body armor, fiber, infrared (IR) spectroscopy, PBO, poly(p-phenylene-2, 6 benzobisoxazole)