Study of curing process of glass fiber and epoxy resin composite by FT-NIR, photoacoustic spectroscopy and luminescence spectroscopy

This article investigates the application of the luminescence spectroscopy technique in steady-state conditions to study the glass fiber–epoxy F155 prepreg. The study was conducted by comparing the results obtained from the intrinsic fluorescence with the data obtained by application of Fourier Transform Near Infrared spectroscopy (FT-NIR) and photoacoustic spectroscopy in the medium infrared spectroscopy (PAS) to the same material. Extrinsic fluorescence of 9-anthroic acid (9-AA) was also used. Infrared spectroscopy with Fourier transform the medium region (FT-IR) was also used to characterize the epoxy resin. Prepregs containing 9-AA or not were heat treated at 121 °C (F-155) for 360 min at a 2 °C/min heating rate. The results obtained by both methods indicated that the cross-linking reaction can be monitored by analyzing the spectrometric changes of the emission bands of the prepreg and 9-AA. The intrinsic emission at 368 nm was used to calculate the conversion degree. The photophysical behavior of 9-AA probe indicated a reduction of free volume of the polymeric matrix with curing process.