*Article* **Prediction of the Miscibility of PBAT/PLA Blends**

**Shen Su 1,2**


**Abstract:** Designing polymer structures and polymer blends opens opportunities to improve the performance of plastics. Blending poly(butylene adipate-co-terephthalate) (PBAT) and polylactide (PLA) is a cost-effective approach to achieve a new sustainable material with complementary properties. This study aimed to predict the theoretical miscibility of PBAT/PLA blends at the molecular level. First, the basic properties and the structure of PBAT and PLA are introduced, respectively. Second, using the group contribution methods of van Krevelen and Hoy, the Hansen and Hildebrand solubility parameters of PBAT and PLA were calculated, and the effect of the molar ratio of the monomers in PBAT on the miscibility with PLA was predicted. Third, the dependence of the molecular weight on the blend miscibility was simulated using the solubility parameters and Flory–Huggins theory. Next, the glass transition temperature of miscible PBAT/PLA blends, estimated using the Fox equation, is shown graphically. According to the prediction and simulation, the blends with a number-average molecular weight of 30 kg/mol for each component were thermodynamically miscible at 296 K and 463 K with the possibility of spinodal decomposition at 296 K and 30% volume fraction of PBAT. This study contributes to the strategic synthesis of PBAT and the development of miscible PBAT/PLA blends.

**Citation:** Su, S. Prediction of the Miscibility of PBAT/PLA Blends. *Polymers* **2021**, *13*, 2339. https:// doi.org/10.3390/polym13142339

Academic Editors: José Miguel Ferri, Vicent Fombuena Borràs and Miguel Fernando Aldás Carrasco

Received: 20 June 2021 Accepted: 14 July 2021 Published: 16 July 2021

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**Keywords:** Flory–Huggins; free energy of mixing; glass transition temperature; group contribution; molecular weight; miscibility prediction; PBAT; PLA; simulation; solubility parameter
