Identification of the Released and Transformed Products during the Thermal Decomposition of a Highly Chlorinated Paraffin.

As plasticizers and flame retardants, highly chlorinated paraffin (CP70) and related products will experience thermal processes during their lifecycle stages. However, the thermal transformation data for CP70 is limited. In this study, we investigated the release and transformation of chlorinated and unchlorinated products during the thermal decomposition of CP70. Large quantities of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) and unsaturated analogues (Cl-polyenes or chlorinated olefins) as well as toxic chlorinated aromatic hydrocarbons were formed synergistically under different thermal conditions. The yield of SCCPs increased gradually in the gas phase, while it decreased in the residue at 200-400 °C. SCCPs can be transformed further and generated mostly polychlorinated biphenyls (PCBs). Oxygen promoted the thermal transformation of SCCPs and MCCPs and decreased the yield in the gas phase at >400-500 °C. In contrast, the yield of both SCCPs and MCCPs increased notably under N2 at 800 °C. Chlorobenzene (CBz), PCBs, and polychlorinated naphthalenes (PCNs) were the main chlorinated aromatic hydrocarbons and obtained a maximum yield at 500-600 °C. The present findings indicate that CP70-containing materials may synergistically generate SCCPs, MCCPs, and other toxic chlorinated compounds during their life cycles.