Investigations on poly(vinyl chloride). I. Evolution of aromatics on pyrolysis of poly(vinyl chloride) and its mechanism

Abstract

Abstract Poly(vinyl chloride) (PVC) alone or mixed with 10 wt‐% and 50 wt‐% TiO 2 , SnO 2 , ZnO, and Al 2 O 3 were pyrolyzed by using a pyrolysis gas chromatograph. Benzene, toluene, ethylbenzene, o ‐xylene, styrene, naphthalene, and various chlorobenzenes were identified. No hydrocarbons could be detected in pyrolysis products of any samples at 200°C. More aromatic hydrocarbons than aliphatic hydrocarbons are released from the PVC–TiO 2 system and in preheated PVC. The contrary result is observed in the PVC–ZnO and PVC–SnO 2 systems. Aromatics having methyl endgroups are easily released from the PVC–ZnO and PVC–SnO 2 systems and at elevated pyrolysis temperature, because methylene groups are easily isolated along the chain by ZnO, SnO 2 and the heating. The release of ethylbenzene o ‐xylene, and chlorobenzenes suggests a repeated dehydrochlorination and recombination of HCl and Cl 2 to double bonds along the chain. Possible decomposition mechanisms of PVC are discussed.