Effects of long exposure to dielectric barrier discharge on commercial blend films of poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS)

INTRODUCTION

The rising demand for biodegradable materials has driven the development of biopolymers such as PBAT/TPS blends, making it essential to assess their stability and performance in different environments. Physical treatments such as non-thermal plasma (NTP) may generate reactive oxygen species (ROS) and induce accelerated surface and bulk modifications. This work aims to evaluate the consequences induced by NTP dielectric barrier discharge (DBD) on commercial films of PBAT-TPS.

METHODS

Commercial PBAT/TPS films were exposed to non-thermal plasma generated by means of dielectric barrier discharge (NTP-DBD) by an Eltech Engineers Lab Corona Treater (Dahisar, Mumbai). The system operates in air atmosphere using a generator with a nominal power of up to 500 W, a frequency of 30 kHz, and an output current of 1.9 A. Films of 100 µm thickness were exposed to irradiation power from 10 to 60 min. Analytical characterisation included colorimetry, FTIR, SEM and DSC to analyse both the bulk and surface modifications.

RESULTS AND DISCUSSION

Abiotic degradation induced by NTP-DBD provoked significant variations observed in colorimetry results, particularly an increase in yellowing with treatment duration. Chemical structure analyses revealed a progressive reduction in the absorbance bands at 1268 cm⁻¹ and 1709 cm⁻¹, corresponding to C–O and C=O stretching vibrations of ester groups in PBAT, indicating ester bond degradation. A decrease in the melting endotherm associated with butylene terephthalate (BT) segments, along with a shift in the melting transition to butylene adipate (BA) phase, was observed with increasing exposure time. Finally, surface electron micrographs demonstrated surface etching after 30 and 60 min of plasma treatment, attributed to the interaction between ROS and the polymer surface.

CONCLUSION

NTP-DBD was demonstrated to promote relevant abiotic degradation of PBAT-TPS-based commercial films, with notable modifications not only at the macroscopic level but also at the molecular scale.

ACKNOWLEDGEMENTS

The authors acknowledge funding from the Agència Valenciana de la Innovació (AVI) through the INNEST/2022/295 project.