Study of thermal degradation mechanisms and stability in poly (vinyl chloride)

Poly (vinyl chloride) or PVC is a commercial and economical polymer thermoplastic that has wide applications in the construction industry, construction, and medical devices. However, PVC exhibits poor thermal stability as it is degraded by a mechanical, thermal or light energy source. Thermal degradation is caused by known zipper decolorization reactions that involve the removal of hydrogen chloride and the formation of conjugated double bonds, leading to a decrease in the mechanical, physical, and chemical properties of the polymer. Studies show that allylic and tertiary chlorides are the most important structural defects in PVC chains that cause thermal degradation in the polymer. In order to increase the thermal stability of PVC, various types of thermal stabilizers are used with different mechanisms including replacement of unstable chlorine atoms, removal of chlorine and hydrogen chloride radicals, reduction in polyone sequences and aromatic alkylation. In the present study, different mechanisms of thermal degradation and various structural defects in the PVC chain are described. Finally, three important categories of thermal stabilizers and their stabilization mechanisms are reviewed.