Tunable Hydrophobicity and Photoluminescence in Polystyrene-Calcium Carbonate Composites with Citric Acid-Induced Porosity

Polystyrene (PS) is widely used in industries like packaging and insulation, but its performance can be enhanced by incorporating calcium carbonate as a filler. To improve polymer-filler compatibility, calcium carbonate was surface-modified with oleic acid, and PS-calcium carbonate composites were synthesized using the melt blending method, followed by citric acid treatment. X-ray diffraction (XRD) and FTIR analyses revealed no chemical interaction between the phases, with a reduction in calcium carbonate content due to citric acid treatment, suggesting partial dissolution of the filler. Scanning electron microscopy (SEM) images showed the formation of cavities in the matrix, especially in TPS3. Hardness testing indicated a decrease in hardness with increasing oleic acid concentration, with TPS3 exhibiting the lowest hardness (63.4 Shore D). Photoluminescence measurements showed a blue shift at lower oleic acid concentrations, while higher concentrations caused a red shift and broader emission, which was stabilized by citric acid treatment. Solvent absorption tests indicated that citric acid-treated composites had an enhanced absorption capacity, with TPS3 showing 38.3 % absorption in vegetable oil, suggesting potential for adsorption applications. Overall, the oleic acid and citric acid treatments significantly modified the mechanical, morphological, and optical properties of PS-calcium carbonate composites, creating tunable materials with potential for sensing applications.