High-Barrier Poly(butylene succinate-co-terephthalate) Blend with Poly(lactic acid) as Biodegradable Food Packaging Films

The insufficient barrier performance of poly(butylene adipate-co-terephthalate) (PBAT) has seriously limited its applications in food packaging and film mulching. Herein, poly(butylene succinate-co-terephthalate) (PBST) was proposed as an alternative material and pilot-prepared with three compositional ratios. It was found that PBST possessed superior water barrier properties and comparable mechanical properties in contrast to PBAT. However, the low strength of PBST could not meet the market demands. Therefore, poly(lactic acid) (PLA) was melt-compounded with PBST to endow a robust mechanical strength for PBST/PLA blends. Then, PBST/PLA blends were prepared into biodegradable films by extrusion blowing. The mechanical, thermal, and rheological properties were investigated. With the increased content of PLA, the tensile strength (TS) of PBST/PLA increased, while the elongation at break (EB) decreased. When the content of PLA was 10 and 20%, the EB of PBST/PLA blends was above 400% and exhibited a compatible system, which was suitable for film blowing. For PBST/PLA (80/20) films, the maximum value of TS and tear strength reached 32 MPa and 124 N/mm, respectively, and displayed superior oxygen, carbon dioxide, and water vapor permeability coefficients to those of PBAT/PLA counterparts. In addition, PBST/PLA blending films with high CO2/O2 permeability ratios (6–8) effectively prolonged the banana freshness period from 7 to 14 days. Accordingly, PBST/PLA films show great potential in high-barrier application scenarios such as food packaging and agriculture mulching.