Polypropylene: A Literature Review of the Thermal Decomposition Products and Toxicity
This report presents a comprehensive literature review of the thermal decomposition products of polypropylene evolved under pyrolytic and oxidative conditions and the acute toxicity of combustion products of this polymer. Generally, the pyrolysis products of polypropylene (300–700°C) were aliphatic saturated and unsaturated hydrocarbons. The combustion of polypropylene in air (200–600°C) produced oxygenated hydrocarbons, aromatic hydrocarbons, aliphatic hydrocarbons, CO, CO2, and H2O. In general, as combustion temperature and time increased, the proportions of oxygenated and aliphatic hydrocarbons decreased, whereas the proportion of aromatic hydrocarbons increased. Using the University of San Francisco/National Aeronautical and Space Administration (USF/NASA) method under the fixed temperature program, time to death in mice caused by the combustion products of polypropylene decreased as the temperature was increased. Under the rising temperature mode, time to death decreased when polypropylene was combusted under airflow as compared to no airflow conditions. CO levels generated by the combustion of polypropylene were sufficient to produce the lethal effects observed. Using a test method developed at the University of Michigan, the combustion products of polypropylene were found to be 26 times more toxic under dynamic conditions (rising temperature) than under static conditions (fixed temperature).