Effect of Caffeic Acid and Natamycin on the Properties of Poly(butylene succinate) for Packaging Applications

This study analyzes the effect of two bioactive additives-caffeic acid and natamycin (Natamax^®)-on the properties of poly(butylene succinate) (PBS) in the context of applications in biodegradable active packaging. Materials containing 1, 3, and 5 wt.% of the additives were prepared by melt blending and characterized in terms of density, rheological behavior (MFR), mechanical properties, thermal stability (TGA), and thermal behavior and crystallization (DSC). Caffeic acid strongly reduced the melt viscosity (reflected by a significant increase in MFR) and, at higher concentrations, led to material stiffening and increased strength at the expense of a pronounced reduction in deformability. Natamycin exhibited a milder rheological effect; at 1 wt.% it simultaneously improved strength and elastic modulus, whereas at higher loadings it deteriorated mechanical performance due to structural effects. Both additives were thermally compatible with PBS; caffeic acid introduced an additional degradation step, while Natamax^® did not significantly alter the degradation mechanism. The results indicate that both the type and concentration of the additive govern the structure-property-function relationships and enable the design of PBS-based packaging materials with controlled performance and functional characteristics.