Using XPS and FTIR spectroscopies to investigate Polyamide 11 degradation on aging flexible risers: Amide V (α CONH, out of plane deformation)CH2 RockingAmide IV (δ[CONH])Interaction between (δ)NH deformation and O=C-N stretchC=O bending (δN- close to CH2)Amide II (-NH-CO-)Amide I (stretch C=O)Esters and impuritiesCH2 symmetric stretchCH2 asymmetric stretchAmide II (Fermi ressonance N-H)N-H bond

Abstract Polyamide 11 is one of the most used thermoplastics to fabricate the pressure sheath of flexible lines widely employed for offshore oil exploration. Therefore, harsh operation conditions are frequently endured, exposing the lines to a myriad of chemical agents while in use, which may promote undesired chemical processes and degradation. In this work, two samples of polyamide 11 sheaths, one that was never put to the intended use and another that operated until decommissioned, were analyzed by spectroscopic techniques, namely XPS and FTIR, with the intent to understand what chemical reactions occur when the polymer is operating. The results showed that, besides hydrolysis that is the most common aging mechanism reported for PA11 in this application, also methanolysis and transesterifications took place due to the presence of alcohols in the riser, and those processes occurred from the nearest part of the core to the farthest with slight variation, an indicative of fluids diffusion.