Evaluation of crystallinity in carbon fiber‐reinforced poly(ether ether ketone) by using infrared low frequency Raman spectroscopy

Abstract

The degree of crystallinity of poly(ether ether ketone) (PEEK) in carbon fiber reinforced composites were evaluated by using infrared low frequency Raman spectroscopy. Reference PEEK samples with varying crystallinity which are evaluated using wide-angle X-ray diffraction (WAXRD) were prepared. These samples were used to create a calibration curve for crystallinity using low frequency Raman spectroscopy. The WAXRD and low frequency Raman methods directly correlated. Carbon fiber reinforced PEEK samples with different cooling rates were prepared and the crystallinity was determined by using low frequency Raman spectrosopy. The crystallinity of the air-cooled sample, water-cooled sample, contact with metal plate and water-cooled sample are 36%, 33%, and 17%, respectively.

Molecular Dynamics Simulation of Poly(Ether Ether Ketone) (PEEK) Polymer to Analyze Intermolecular Ordering by Low Wavenumber Raman Spectroscopy and X-ray Diffraction

“…Before presenting computational analysis, the experimental findings are reviewed briefly. The experimental data have been reported previously [7] but here we newly processed the data in a form suitable for comparison with the computational results.…”

“…Intermolecular modes are expected to be more sensitive to the crystallinity, because the intermolecular distances and angles and chain alignment in polymers will be affected by the crystallinity. A team including some of the present authors has reported the use of a low-frequency Raman signal to evaluate the crystallinity of PEEK [7]. Although they found that the intensity of a Raman signal changed during crystallization as explained in the next section, the mechanism has not been elucidated.…”

“…To compare the calculation with the experiments, WAXRD patterns and Raman spectra were measured on the samples annealed at various temperatures up to 300 • C for 2 h. The sample material was a quenched PEEK thin film with a thickness of 50 mm (Victrex APTIV film, grade 1000). Details of the experiment are described in [7]. WAXRD was measured by using Rigaku Ultima IV (rotating anode, 40 kV 30 mA) operating with CuKa X-ray (wavelength 1.5406 Å).…”

“…There are various techniques for the evaluation of the crystallinity of polymers such as wide-angle X-ray diffraction (WAXRD), small-angle X-ray diffraction (SAXS), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and Raman microscopy [6,7]. Among them, Raman microscopy, which takes Raman spectra under the focus of an objective lens, is probably the only readily available technique [8].…”

“…Polymers 2022, 14, 5406 2 of 13 There are several reports on the application of Raman spectra for the evaluation of the crystallinity of PEEK [6,7,[11][12][13][14][15]. Usually, the frequency shift of fundamental vibration modes involving a single or several covalent chemical bonds (intramolecular modes) is used to characterize the crystallinity.…”