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Abstract:
This study presents the results of investigations on the influence of raw material type and synthesis method of cadmium yellow on the electrokinetic potential of pigment particles and the sedimentation stability of the resulting dispersions
in various chemical environments. Pigments were synthesized from cadmium salts (chloride, sulfate, nitrate, and carbonate) using sodium sulfide or elemental sulfur as sulfur sources. Two synthesis routes were applied: (1) precipitation of
the pigment from solution, followed by filtration, drying at 60 °C, and calcina-tion at 600 °C in acidic and alkaline media; and (2) direct reaction of cadmium carbonate with sulfur at 600 °C. The materials were characterized using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The zeta potential of
the particles was measured at different pH values, and dispersion stability was evaluated by turbidimetric analysis (Turbiscan). The obtained pigments were mixtures of compounds, with cadmium sulfide (CdS) being the predominant component. The chemical composition depended on the synthesis route and the
calcination process. A correlation was found between the electrokinetic potential,sedimentation stability, and chemical composition of the pigments. Calcination significantly affected surface properties, while the presence of chloride, sulfite,
sulfate, and carbonate species modified the electrokinetic potential. Acidic envi-ronments were found to enhance the sedimentation stability of cadmium-based pigments. The findings highlight the importance of synthesis conditions for the
surface chemistry, electrokinetic behavior, and sedimentation stability of cad-mium-based pigments in aqueous systems.

Abstract:
In this work, we developed and characterized the membranes based on polyvinyl chloride plastisol modified with silver nanoparticles deposited on silica. The aim of the study was to obtain a functional PVC plastisol composite for use as linings and protective coatings, with improved mechanical, thermal, and antimicrobial properties. The plastisol was prepared by mixing PVC resin with a plasticizer (bis(2-ethylhexyl) adipate). Silver nanoparticles were produced by two methods: chemical reduction using sodium citrate and gum arabic, and these particles were deposited on Aerosil®200 silica. These composites were introduced into plastisol at different concentrations and then processed into films by gelation and hydraulic pressing. The formation of silver nanoparticles was confirmed by UV-Vis spec-trophotometry, and the morphology of the composites was examined by scanning electron microscopy. Further char-acterization of the materials included infrared spectroscopy, thermomechanical analysis, mechanical property testing, and thermogravimetric analysis. Mechanical properties such as Young’s modulus, tensile strength, and elongation at break were determined by static tensile tests. Shore hardness tests were also performed to evaluate the stiffness of the composites. The antimicrobial activity of the membranes was evaluated according to ASTM method E2149-01 using reference strains of S. aureus and E. coli. Studies have shown that silver nanoparticles effectively inhibited the growth of E. coli, especially at higher concentrations of AgNPs, while they had no effect on S. aureus. AgNPs modi-fied membranes obtained from the reduction of AgNO₃ with sodium citrate and deposited on silica showed higher microbiological activity than those with AgNPs reduced with gum arabic. An optimal filler content in the range of 1 to 1.5% provides the most favorable combination of mechanical, thermal, and antibacterial properties.

Keywords:
plastisol, silver nanoparticles