Design of TPS/PBAT Flexible Biodegradable Blown Films Modified by PLA and Talc

This work investigates the combined influence of talc (0–10 wt%) and polylactide (PLA, 0–10 wt%) on thermoplastic starch/poly(butylene adipate-co-terephthalate) (TPS/PBAT) biodegradable blown films at a pre-industrial level. A series of 16 formulations was successfully prepared via twin-screw extrusion and subsequently processed into films using blown film extrusion. FTIR confirmed the coexistence of TPS, PBAT, and PLA phases. Morphological analysis revealed that PLA enhanced phase compatibility and matrix homogeneity, while moderate talc contents improved surface uniformity; however, excessive talc induced microstructural irregularities, unless high PLA contents were formulated. DSC analysis showed that talc acted as a nucleating agent for PBAT, raising the crystallisation temperature (Tc) from 83.9 °C to 95.7 °C, while PLA slightly modulated both crystallisation and melting behaviour (Tm₁ ≈ 116–118 °C; Tm₂ ≈ 148–151 °C). Mechanical results indicated that PLA significantly increased stiffness and strength, with the Young’s modulus rising from 29 MPa to 286 MPa and yield strength from 4.6 MPa to 9.3 MPa, whereas talc contributed with additional reinforcement. The optimal balance between stiffness and ductility was achieved at intermediate-to-high PLA levels (7–10 wt%) combined with 5–10 wt% of talc, maintaining elongation at break between 450% and 700%. These findings provided valuable guidelines for tailoring compostable TPS/PBAT-based biofilms to meet the performance and sustainability requirements of flexible packaging applications.