Ultrasonic chemo-thermal degradation of commercial poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) blends

• Published in: Polymer degradation and stability 2025-02, Vol.232, p.111133, Article 111133
• Main Authors: Gutiérrez-Silva, K., Jordán-Silvestre, A., Cháfer, A., Muñoz-Espí, R., Gil-Castell, O., Badia, J.D.
• Format: Article
• Language: English
• Subjects: Abiotic degradation; Biopolymer blends; Chemo-thermal treatment; Poly(butylene adipate-co-terephthalate) (PBAT); Thermoplastic starch (TPS); Ultrasound-assisted hydrolysis
• ISSN: 0141-3910
• DOI: 10.1016/j.polymdegradstab.2024.111133

•Ultrasonic chemo-thermal treatment promoted degradation in PBAT/TPS blends.•Acidic, neutral, and basic media induced different degradation behaviors.•Surface deterioration and disintegration were more relevant in the alkaline medium.•Ultrasound always enhanced degradation, particularly for TPS-rich compositions.•Promoting accelerated abiotic degradation may improve the eventual biodegradation. Blends of poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) are promising materials for sustainable packaging and biodegradable agricultural products. However, biodegradability is sometimes compromised by insufficient polymer chain breakdown when exposed to biodegradation environments. This study aims to explore the consequences of short-time accelerated abiotic degradation processes to induce polymer chain cleavages before eventual biodegradation in a circular economy paradigm. Specifically, the degradation of commercial PBAT/TPS blends was investigated, with varying compositions and incorporating additives as plasticising and compatibility agents. The materials were exposed to different chemo-thermal conditions, including acid, neutral and alkaline pH levels. In addition, ultrasound was considered to boost chemo-thermal degradation. The process was monitored by macroscopic appearance analysis, water contact angle, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The chemo-thermal treatment led to surface deterioration, pore and defect generation, and eventual disintegration of the materials. Mass loss due to the release of the hydrophilic fraction, mainly TPS, was demonstrated. Degradation of the PBAT fraction was also proved, given the formation of new carboxyl and carboxylate groups, resulting in critical changes in the crystalline morphology and hydrophilic behaviour. Notably, the alkaline medium promoted the most severe material degradation, accentuated in all cases with ultrasound, mostly for the blend with the greatest TPS content. These findings provide a foundation for developing targeted strategies to accelerate the degradation of PBAT/TPS-based materials, particularly in end-of-life scenarios where chemo-thermal pre-treatments could facilitate ulterior biodegradation.