Study of the influence of saline solutions in carbon/epoxy composite by luminescence, Raman and UATR/FT-IR spectroscopy

The purpose of this work was to investigate the states of water in carbon-epoxy composite under influence of saline solutions using gravimetric analysis and the following spectroscopic techniques: photoluminescence, Raman and UATR/FTIR. Two sets of samples were prepared after the curing process. The first one was submitted to saline vapor and the other was immersed in the saline solution. All samples were heat-treated at 40, 60 and 80 degrees C for periods of 7, 14, 21 and 28 days. The dissolved ions in the artificial seawater tend to inhibit the water absorption of the immersed samples that presented similar amounts of water in relation to the samples submitted to saline vapor. The relative intensity decreasing of emission spectra indicated that the nonradiative decay pathways are predominant in relation to the radiative ones due to the increasing of mobility of the polymeric chains. The main changes of the Raman spectra were the decreasing of the relative intensity of the bands at 1610 and 1511 cm(-1) attributed to the aromatic rings. This behavior also indicated the enhancement of conformational freedom of the polymeric chains due to the plasticization. The FT-IR band assigned to hydroxyl groups shifted towards lower wavenumbers suggesting interaction of water molecules with OH groups.