SPECIFIC FEATURES OF THE TECHNOLOGY FOR OBTAINING EXTRUDED POLYMER COMPOSITIONS BASED ON STARCH ADDITION WITH CITRIC ACID

Abstract

The aim of this study was to establish the patterns of structure formation and to conduct a comprehensive investigation into the physicochemical characteristics of biodegradable extruded materials based on a blend of starch and polyvinyl alcohol (PVA). The primary scientific interest focused on evaluating the effect of adding citric acid directly into the polymer composition on component compatibility and the performance properties of the resulting composites. The experimental phase involved the development and optimization of polymer systems based on native starch and PVA. To ensure the necessary thermoplasticity of the melt, glycerol was introduced as a plasticizer. Structural modification was achieved by incorporating 1 % and 2 % (by weight) of citric acid into the polymer composition. Fouriertransform infrared spectroscopy (FTIR) in Attenuated Total Reflectance (ATR) mode was employed to identify structural transformations and verify intermolecular interactions. Spectral analysis confirmed the occurrence of chemical interactions within the system, evidenced by the appearance of characteristic absorption bands in the 1730–1750 cm⁻¹ region, corresponding to the stretching vibrations of ester groups. It was found that the presence of citric acid promotes more intensive interchain cross-linking, leading to increased mechanical strength and a significant reduction in the material’s hydrophilicity. Evaluation of the sorption capacity showed that samples containing citric acid possess considerably higher moisture resistance compared to basic formulations without acid, which is a critical parameter for their practical implementation. The scientific novelty of this work lies in establishing a direct correlation between the amount of citric acid added during the extrusion process and the dynamics of ester bond formation, which determine the final physicochemical properties of the composite. For the first time, the nature of changes in the intensity of hydroxyl and carbonyl group absorption bands in the starch/PVA system was described in detail as a function of the acid content under high-temperature shear conditions. The practical significance of the results lies in the development of an efficient one-step technology for the production of biodegradable materials, enabling the creation of competitive eco-friendly products (from packaging to agricultural components) based on renewable raw materials.