What are the differences in thermal degradation between PVC and polypropylene?

Thermal degradation behaviors of PVC (Polyvinyl Chloride) and polypropylene (PP) differ significantly due to their distinct chemical structures and stability under heat. PVC begins degrading at lower temperatures (around 140°C), releasing hydrochloric acid (HCl) as a byproduct, which accelerates further decomposition. In contrast, polypropylene exhibits higher thermal stability, with degradation starting above 300°C, primarily breaking down into hydrocarbons without corrosive emissions.

PVC's degradation is highly dependent on additives like plasticizers, which can lower its heat resistance. Polypropylene, being a hydrocarbon polymer, degrades through chain scission, resulting in reduced molecular weight but fewer hazardous byproducts. Industrially, PP is preferred for high-temperature applications, while PVC requires stabilizers to mitigate thermal degradation risks. Understanding these differences is crucial for material selection in manufacturing and recycling processes.