A non-destructive method using low-field nuclear magnetic resonance for characterizing the molecular weight of PBAT during thermo-oxidative degradation

The molecular weight is an important indicator for assessing the aging of polymers. However, existing methods for characterizing the molecular weight of polymers involve complex procedures and destructive tests. Therefore, efficient, rapid, and non-destructive testing methods would be a key development in material degradability evaluation. In this paper, we studied the thermo-oxidative aging process of polybutylene adipate terephthalate (PBAT) using a low-field nuclear magnetic resonance (LF-NMR) analysis method. The degradation mechanism of PBAT during thermo-oxidative aging is characterized by its low-field nuclear magnetic resonance decay curve and inversion curve. A two-component LF-NMR fitting analysis reveals that the thermo-oxidative degradation of PBAT conforms to a random fracture mechanism. Furthermore, a correlation between number average molecular weight and LF-NMR relaxation time during thermo-oxidative degradation of PBAT was constructed, with a correlation coefficient R2 greater than 0.97. The error between the correlation equation used in the molecular weight detection of PBAT and the actual test is less than 10%, indicating that it is feasible and reliable to characterize the number average molecular weight of materials by applying the LF-NMR relaxation time.

Automated summary

This study investigated the thermo-oxidative aging process of PBAT using LF-NMR analysis and found that the degradation mechanism of PBAT during thermo-oxidative aging is random fracture. A correlation between number average molecular weight and LF-NMR relaxation time during thermo-oxidative degradation of PBAT was established. The results indicate that characterizing the molecular weight of PBAT using LF-NMR relaxation time is feasible and reliable.