Evaluation of degradation behavior of modified hydrotalcite/PVC/chitosan composite films

Poly(vinyl chloride) (PVC) is a widely used thermoplastic in the polymer industry due to its low cost, processability, and wide application. However, its limited resistance to thermal and photochemical degradation limits its long-term use. Therefore, it is important to develop additive systems to increase PVC's strength and reduce plasticizer migration. To this end, various additives have been used to increase the strength of PVC-based composite films, and the degradation behavior of the resulting films has been investigated. In this study, dioctyl terephthalate (DOTP) plasticizer, calcium stearate-zinc stearate (CaSt2–ZnSt2) stabilizers, epoxidized soybean oil (ESBO), hydrotalcite, chitosan, glutaraldehyde, and crosslinkers such as 1-(3- dimethylaminopropyl)-3-ethylcarbodimide (EDC) were added to PVC plastisols. The prepared plastisols were applied to glass surfaces to obtain films of specific thicknesses, and these films were subjected to thermal and UV aging. Structural changes in the films were determined by Fourier Transform Infrared (FT-IR) spectroscopy, polyene formation was monitored by UV-Vis spectroscopy, and activation energies were calculated. Plasticizer migration was evaluated via the diffusion coefficient. Mass losses were measured by thermogravimetric analysis (TGA), and the glass transition temperature (Tg) was measured by DSC analysis. The surface morphology of the films was examined using a scanning electron microscope (SEM). Biocompatibility and biodegradability tests were performed on the films. Tensile tests were performed on plastisol sheets to examine their mechanical properties (modulus of elasticity, toughness, etc.). Particle size distribution, surface charge, and stability of the samples were also examined using potential testing. In this thesis, the strength of PVC systems was comprehensively evaluated from different perspectives using the methods used. Both structural changes and strength under environmental conditions were examined multidimensionally. The findings indicate that the addition, modification, and cross- linking of hydrotalcite and chitosan significantly reduced plasticizer migration and increased the resistance of PVC-based composites to thermal, photochemical, and biological degradation. In addition to improving the resistance of PVC to environmental conditions, these additive systems are thought to contribute to expanding the material's usage area, especially in applications requiring biocompatibility such as medical devices.