## 1 Introduction
Additionally, the processability of these materials can also be affected by their possible incompatibility. During the extrusion and compounding process, it is crucial for the components to mix uniformly to ensure the homogeneity of the final material. However, if the polymers are not compatible with each other, phenomena such as phase separation or aggregate formation can occur, resulting in a non-uniform distribution of properties in the composite material [36]. Another factor to consider is the thermal stability of the mixture. Since starch is sensitive to heat and tends to degrade at high temperatures, compatibility with biodegradable polyesters can affect the thermal stability of the composite material. This may limit the processing conditions and the final applications of the material, especially if resistance to high temperatures is required [37]. In summary, the possible incompatibility between thermoplastic starch and biodegradable polyesters can pose significant challenges in the development of composite materials. However, overcoming these challenges is crucial to fully harness the advantages of each component and develop sustainable and functionally robust packaging solutions. In this study, this aspect will be addressed by optimizing processing conditions and selecting compatible additives to improve compatibility between the materials and obtain a composite material with improved properties and a wide range of potential applications [38,39]. These additives are specifically designed to enhance the interaction among the mixture components, promoting uniform dispersion of the polymers and facilitating the formation of a more effective interface between them. Among the most common compatibilizing additives are coupling agents and matrix compatibilizers. Coupling agents, such as silanes and isocyanates, function by chemically reacting with functional groups present in the polymers, promoting adhesion between them. On the other hand, matrix compatibilizers, such as block copolymers and graft copolymers, act by adsorbing onto the interface between the polymers, reducing interfacial energy, and improving compatibility between them [40,41]. The challenges arising from the incompatibility between thermoplastic starch (TPS) and biodegradable polyesters must be addressed to ensure homogeneous blending. To achieve this, compatibilizers like Vinnex\({}^{\text{\text{\textregistered}}}\) and Joncryl\({}^{\text{\text{\textregistered}}}\) can be used to improve the interaction between the components of the blend, enhancing the overall material properties. Vinnex, a maleic acid-based additive, enhances compatibility by reacting with functional groups in both starch and polyesters, forming chemical bonds that promote interfacial adhesion. It also acts as a plasticizing agent, improving processability and enhancing the mechanical properties of the composite material [42, 43, 44, 45]. On the other hand, Joncryl, a reactive chain extender, interacts onto the polymer interface, reducing interfacial energy and promoting uniform dispersion. It not only improves interfacial compatibility but also enhances the thermal stability and impact resistance of the material [31, 44, 45, 46, 47, 48]. These improvements result in composite materials with a wider range of potential applications, particularly in the development of more sustainable packaging solutions [49, 50]. In this study, Vinnex and Joncryl were selected as compatibilizing additives to improve the interaction between thermoplastic starch and biodegradable polyesters during the compounding process, and their effects on the properties of the composite material--such as interfacial compatibility, thermal stability, mechanical resistance, and biodegradability--were evaluated. The objective was to develop a polymer blend with enhanced properties that can contribute to the search for more sustainable solutions for packaging and other plastic products.