Fourier transform infra-red (FTi.r.) spectroscopy was used to study the thermal degradation that occurs in composite materials consisting of poly(ether ether ketone) (PEEK) reinforced with carbon fibres. Spectra were measured by diffuse reflectance for samples of prepreg and moulded laminate exposed to temperatures in the range 400-485°C for different periods of time in both air and nitrogen atmospheres. In spite of some spectral distortion arising from front-surface reflection, useful information can be obtained concerning the reactions that occur and their relative rates under different conditions. The reactions and their activation energies are found to be similar to those observed for neat PEEK film, described in a previous publication. In an inert atmosphere, the degradation involves a pyrolytic-type mechanism which produces a new carbonyl species absorbing at 1711 cm- 1, probably a fluorenone-type structure; the activation energy for this process is around 240 kJ mol- 1. In an oxidizing atmosphere, the same species is produced but at a faster rate, with an activation energy of around 200kJmol-1. In addition there is a second reaction which requires the participation of oxygen and produces a species absorbing at 1739 cm- 1, probably ester groups; the activation energy for this reaction is about 130kJmol-L Some samples were also analysed by photoacoustic spectroscopy. Within the limits of the technique, no significant difference could be discerned between the degradation behaviour of PEEK-carbon composites and that of neat PEEK films.
Посилання на статтю:
Fourier transform infra-red spectroscopic study of thermal degradation in poly(ether ether ketone)-carbon composites / K. C. Cole and I. G. Casella // Polymer. – 1993. – Vol 34. – P. 740-745.