Fig. 1. Optical images of UHMWPE (a, d), HDPE (b, e), and LDPE (c, f) before and after post radiation oxidation (absorbed dose of 100 kGy, oxygen partial pressure of 5×10⁵ Pa, oxidized at room temperature for 47 d)

Fig. 2. DSC images of UHMWPE (a), HDPE (b), and LDPE (c) before and after radiation and oxidation(absorbed dose of 100 kGy, oxygen partial pressure of 5×10⁵ Pa, oxidized at room temperature for 47 d) (color online)

Fig. 3. FTIR spectra and OI values with time for the post radiation oxidation of UHMWPE (a, b), HDPE (c, d), and LDPE (e, f) under room temperature conditions (absorbed dose of 100 kGy, oxygen partial pressure of 5×10⁵ Pa, oxidized at room temperature for 47 d) (color online)

Fig. 4. Images of OI values with time for the post radiation oxidation of UHMWPE (a) and HDPE (b) at different temperatures (room temperature, 50 °C, 70 °C, and 90 °C)(Absorbed dose of 100 kGy, oxygen partial pressure of 5×10⁵ Pa, oxidized for 24 h)

Fig. 5. Images of OI values with time for the post radiation oxidation of UHMWPE (a, c, e) and HDPE (b, d, f) at different oxygen partial pressures (2×10⁴ Pa, 1×10⁵ Pa, 3×10⁵ Pa, 5×10⁵ Pa, and 9×10⁵ Pa) and different temperatures (a, b) room temperature, (c, d) 50 °C, and (e, f) 70 ℃ (absorbed dose of 100 kGy, oxidized for 24 h)

Fig. 6. Images of OI values with time for the post radiation oxidation of UHMWPE (a, b) and HDPE (c, d) at different absorbed doses (50 kGy, 100 kGy, 150 kGy, 200 kGy, and 300 kGy) and at different temperatures (a, c) 50 ℃ and (b, d) 70 ℃ (oxygen partial pressure of 5×10⁵ Pa, oxidized for 24 h)

Fig. 7. Mechanism of oxidation process by PE post-radiation