Abstract:
In this study, the mechano-chemical properties of aromatic polymer polyetheretherketone
(PEEK) samples, irradiated by high energy electrons at 200 and 400 kGy doses, were investigated
by Nanoindentation, Brillouin light scattering spectroscopy and Fourier-transform infrared spectroscopy
(FTIR). Irradiating electrons penetrated down to a 5 mm depth inside the polymer, as shown
numerically by the monte CArlo SImulation of electroN trajectory in sOlids (CASINO) method. The
irradiation of PEEK samples at 200 kGy caused the enhancement of surface roughness by almost
threefold. However, an increase in the irradiation dose to 400 kGy led to a decrease in the surface
roughness of the sample. Most likely, this was due to the processes of erosion and melting of the
sample surface induced by high dosage irradiation. It was found that electron irradiation led to
a decrease of the elastic constant C11, as well as a slight decrease in the sample’s hardness, while
the Young’s elastic modulus decrease was more noticeable. An intrinsic bulk property of PEEK is
less radiation resistance than at its surface. The proportionality constant of Young’s modulus to
indentation hardness for the pristine and irradiated samples were 0.039 and 0.038, respectively. In
addition, a quasi-linear relationship between hardness and Young’s modulus was observed. The
degradation of the polymer’s mechanical properties was attributed to electron irradiation-induced
processes involving scission of macromolecular chains.