Real-Time Pyrolysis Dynamics of Thermally Aged Tire Microplastics by TGA-FTIR-GC/MS

Abstract

Tire wear particles (TWPs), as a type of thermosetting microplastic (MP), accumulate in aquatic environments due to their wide application in road traffic globally. The increase in temperature because of friction heat may cause aging of tire materials, inducing water evaporation, additive volatilization, polymer decomposition, and may pose serious potential risks to aquatic and terrestrial ecosystems. However, research on real-time pyrolysis dynamics of thermally aged tire MPs is very limited. In this study, a thermogravimetric analyzer coupled with Fourier transform infrared spectrometry and gas chromatography-mass spectrometry (TG-FTIR-GC/MS) was used to investigate pyrolysis behaviors and products of thermally aged tire MPs. FTIR analysis indicated that the main pyrolysis gases included carbon dioxide, carbon monoxide, aliphatic compounds, aromatic compounds and carbonyl compounds. The GC/MS analysis further determined the main pyrolytic products, including methylbenzene, styrene, m-xylene and D-limonene. These data combined with TG analysis revealed that the main pyrolytic products of TWPs were released at 400–600 °C. Moreover, the results showed that the number of aliphatic/aromatic compounds released increased in short-term thermo-oxidative aging but decreased in long-term thermo-oxidative aging. Moreover, the aged TWPs presented higher released amounts of styrene and methylbenzene but lower amounts of D-limonene compared to the original TWPs. These results can provide new insights into the evaluation method of TWP aging and a better understanding on TWP fate in aquatic and terrestrial environments.