Degradation of Polymeric Materials and Risk Assessment of Recycling Processes

Recycling of waste plastics has been practiced in a variety of ways, such as thermal, material, and reuse. The plastics may degraded during the use and recycling process under stresses of thermal, mechanical, and UV irradiation. The degradation of polymeric materials should generate low-molecular weight chemicals such as oligomers and monomers due to the decomposition reaction of polymers induced by heat, UV irradiation. Some polymeric materials used with additives such as plasticizer, or flame retardants. These additives can be transformed into low-molecular weight chemicals by the chemical reactions. These lower-molecular weight chemicals including additives should be released into the environment during the use and recycling of plastics, and may be taken by humans. Uptake of harmful chemicals included should may cause risks for human health. In this study, we have developed a measurement method of chemicals emitted into the gaseous phase from plastic materials under various conditions based on the passive sampling method. The method was applied to some commercially available plastic materials such as PE, PP, PVC, PC. We confirmed the emissions of various kinds of volatile and semi-volatile chemicals (VOCs and SVOCs), and the emission rates of these chemicals were obtained as a function of time, temperature, and UV irradiation strength. Based on the emission rates and toxicity indexes of the emitted chemicals, we conducted risk assessment of the recycling process of plastics.