The effects of heat stabilizers on the heat stability of plasticized PVC

The PVC is subjected to deterioration due to the heat treatments during its production and service life. Stabilizers protect the polymer from thermal, oxidative and UV light generated during processing or use of it. In this study, the effect of thermal stabilizer type on the thermal stability and color change of plasticized PVC (p-PVC) systems to be used in flexible PVC applications such as food packaging has been investigated. Firstly p-PVC plastisols were obtained. For plastisol preperation di-octyl terephthalate (DOTP) was used as plasticizer, some metal salts and their mixtures, maleimides, thiols, hydrotalcite were used as heat stabilizers. Small aliquots of plastisols were spreaded at 150 μm thickness on glass plates and were cured (gelled) for 15 minutes in an air-circulating oven set to 160°C and plastijel films were obtained. The films were heat treated at temperatures of 100 and 150 ° C for up to 420 minutes. The thermal degradation mechanisms of heat treated films were evaluated by Thermal Gravimetric Analysis (TGA). Structural changes and oxidation indices in the materials were monitored by Fourier Transform Infrared (FT-IR) spectroscopy. The concentration of the polyene sequences during heat treatment were determined by UV-vis spectroscopy. Color change of the films after degradation were followed by the colorimetry. The diffusion of plasticizers from the prepared p-PVC films into the air was found by mass loss. Kinetic parameters for diffusion (diffusion rate constant, activation energy) were calculated. It is believed that the results will contribute to the thermal stability of PVC by different stabilizers and blends.