*Article* **Gum Rosin as a Size Control Agent of Poly(Butylene Adipate-Co-Terephthalate) (PBAT) Domains to Increase the Toughness of Packaging Formulations Based on Polylactic Acid (PLA)**

#### **Miguel Aldas 1,2,\*, José Miguel Ferri 1,\*, Dana Luca Motoc <sup>3</sup> , Laura Peponi <sup>4</sup> , Marina Patricia Arrieta 5,6 and Juan López-Martínez <sup>1</sup>**


**Abstract:** Gum rosin (GR) was used as a natural additive to improve the compatibility between polylactic acid, PLA, and poly(butylene adipate-co-terephthalate, PBAT, blended with 20 wt.% of PBAT (PLA/PBAT). The PBAT was used as a soft component to increase the ductility of PLA and its fracture toughness. The coalescence of the PBAT domains was possible due to the plasticization effect of the GR component. These domains contributed to increasing the toughness of the final material due to the variation and control of the PBAT domains' size and consequently, reducing the stress concentration points. The GR was used in contents of 5, 10, 15, and 20 phr. Consequently, the flexural properties were improved and the impact resistance increased up to 80% in PLA/PBAT\_15GR with respect to the PLA/PBAT formulation. Field emission scanning electron microscope (FESEM) images allowed observing that the size of PBAT domains of 2–3 µm was optimal to reduce the impact stress. Differential scanning calorimetry (DSC) analysis showed a reduction of up to 8 ◦C on the PLA melting temperature and up to 5.3 ◦C of the PLA glass transition temperature in the PLA/PBAT\_20GR formulation, which indicates an improvement in the processability of PLA. Finally, transparent films with improved oxygen barrier performance and increased hydrophobicity were obtained suggesting the potential interest of these blends for the food packaging industry.

**Keywords:** polylactic acid; PLA; poly(butylene adipate-co-terephthalate; PBAT; gum rosin; biodegradable polymers; barrier properties
