Fig. 1. Structure schematic diagram of in-situ aging evaluation system^[11]

Fig. 2. ATR-FTIR spectra of (a) PA6 and (b) PA66 after natural aging different periods of time

Fig. 3. Change against natural aging time in (a) N—H and (b)C=O relative absorbance of PA6 and PA66

Fig. 4. IR spectra of unaged PA6 during in-situ aging test

Fig. 5. CO₂ emission over time of PA6 (a) and PA66 (b) with different natural aging time

Fig. 6. Change against natural aging time in CO₂ emission of PA6 and PA66

Fig. 7. Change against temperature and humidity in CO₂ emission of PA6 (a) and PA66 (b) during in-situ aging test