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Chemical and Physical Characterization of Poly(p-phenylene benzobisoxazole) Fibers Used in Body Armor



Joannie W. Chin, E Byrd, Amanda L. Forster, Xiaohong Gu, Tinh Nguyen, Kirk D. Rice, Walter J. Rossiter Jr, S J. Scierka, John R. Sieber, Paul E. Stutzman, Li Piin Sung


Problems with the performance and durability of body armor based on poly(p-phenylene benzobisoxazole (PBO) fiber became apparent in the summer of 2003, when PBO-based body armor that was less than 8 months was penetrated by a bullet. Mechanical testing of the yarns taken from the penetrated vest indicated a 30 % decrease in tensile strength relative to yarns taken from new, unworn PBO-based vests of the same model. A number of analytical metrologies were used to characterize the yarns, including chemical (elemental and molecular) analysis, mechanical testing, thermal analysis and microscopy. Attenuated total reflectance (ATR) infrared analyses of the yarns revealed differences in their degree of hydrolytic degradation as determined by the presence of benzamide structures. The rank order of reduction in benzamide, which corresponds to benzamide hydrolysis, correlates with the rank order reduction in tensile strengths for these same yarns.
NIST Interagency/Internal Report (NISTIR) - 7237
Report Number


attenuated total reflectance (ATR), body armor, fiber, hydrolysis, infrared (IR) spectroscopy, poly(p-phenylene benzobisoxazole) (PBO), yarn


Chin, J. , Byrd, E. , Forster, A. , Gu, X. , Nguyen, T. , Rice, K. , Rossiter, W. , Scierka, S. , Sieber, J. , Stutzman, P. and Sung, L. (2006), Chemical and Physical Characterization of Poly(p-phenylene benzobisoxazole) Fibers Used in Body Armor, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 19, 2024)
Created May 1, 2006, Updated November 10, 2018