## 1 Introduction
Plasticizers and other additives can be incorporated during this process to improve compatibility and the final properties of the composite material [24,25, 26]. Among these additives, compatibilizers play a critical role in addressing the incompatibility challenges between TPS and biodegradable polyesters. For instance, reactive compatibilizers such as glycidyl methacrylate (GMA) and maleic anhydride (MA) have been shown to improve interfacial adhesion and phase dispersion, significantly enhancing mechanical and thermal properties [27,28]. In addition, although thermoplastic starch has great potential as a biodegradable material, its practical use is significantly enhanced when blended with biodegradable polyesters. These combinations not only improve the mechanical properties and stability of TPS but also allow its application in a wider range of products, contributing more effectively to the reduction of plastic pollution and the promotion of a more sustainable future [29]. For example, Vinnex, a maleic acid-based compatibilizer, improves compatibility by reacting with functional groups in both starch and polyesters, forming chemical bonds that promote interfacial adhesion [5]. Similarly, Joncryl, a reactive chain extender, reduces interfacial energy, enhancing dispersion and thermal stability [28; 30]. Although TPS constitutes a smaller fraction of the blends (up to 25 wt%), its modification is essential to overcome its inherent limitations such as brittleness and water sensitivity. By tailoring TPS with compatibilizers, its inclusion modifies the properties of the matrix itself, such as its crystallinity, interfacial adhesion, and biodegradability. The compatibilizers used in this study, such as Joncryl and Vinnex, act not only to address TPS limitations but also to improve the homogeneity and performance of the PBAT or PBSA matrix. This interaction transforms the blend into a cohesive material where TPS, despite its lower percentage, acts as a structural modifier that significantly impacts the mechanical and thermal properties of the matrix. For instance, Joncryl acts as a chain extender, improving the dispersion of TPS in the polyester matrix and minimizing phase separation, as highlighted by [PERSON] et al. (2023) and [PERSON] et al. (2019) [27; 31]. The focus on improving TPS properties is driven by its critical role in providing biodegradability to the blends. PBAT and PBSA are already known for their flexibility and thermal stability, but without TPS, the blends would lack the required environmental benefits. By enhancing the properties of TPS through compatibilizers, the material becomes suitable for demanding applications, such as flexible packaging, without compromising valorisation routes [28; 32]. While PBAT and PBSA provide the mechanical and thermal stability required for packaging applications, the incorporation of modified TPS enables a significant reduction in fossil-based content and improves the environmental profile of the blends. Compatibilizers ensure efficient integration, as reported by [PERSON] et al., leading to enhanced phase dispersion and overall performance [28]. Despite the numerous advantages offered by biodegradable polyesters when combined with thermoplastic starch (TPS), it is important to note that compatibility between these materials can be challenging. The main reason for this possible incompatibility lies in the differences in chemical structure and physical properties of each component [33]. Starch is a natural polysaccharide composed mainly of glucose, which has an amorphous and semicrystalline structure. On the other hand, biodegradable polyesters such as polybutylene succinate-co-adipate (PBSA) and polybutylene adipate-co-teerephthalate (PBAT) are synthetic polymers that have a more linear structure and are less polar than starch. This disparity in molecular structure can result in a lack of interaction between the components, making it difficult to form a homogeneous mixture and obtain improved properties in the composite material [34; 35].