Raman and FT-IR Based Methodology Development to Assess Flexible Pipelines Pressure Barrier Degradation in Offshore Installations of the Oil and Gas Industry

The recommended standard technique for monitoring the degradation of polyamide 12 (PA-12) is viscosimetry, through measurements of inherent viscosity (IV) to obtain the values of Corrected Inherent Viscosity (CIV). The CIV values were used as reference to correlate with Raman and IR results. PA-12 pristine samples and those submitted to ageing in reactors with controlled pressure and supercritical CO₂ conditions were analyzed. The specimens were immersed in mineral water (pH 4.0), at a temperature of 120 °C for a period of up to 45 days. From the Raman spectra the ν_asCH2 vibration at 2924 cm^{– 1} seems to be a sensitive spectral probe of PA-12 hydrolytic degradation, therefore the relative intensity decrease of pristine and aged samples was used to compare RAMAN and CIV results. From FTIR spectra, a variation in the intensity of the bands attributed to the α and γ phases, at ~ 1560 and 1545 cm^{– 1}, respectively, was observed, which might be related to the degradation/ageing of the polymer. After analyzing samples submitted to different ageing conditions, there are good evidences that an analyses protocol of Raman and FTIR give consistent qualitative information on the degradation of PA-12, and therefore, is a new alternative for monitoring the hydrolytic degradation of PA-12, thus eliminating the use of toxic organic solvents, reducing the analysis time and bringing information about the degradation mechanism.