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

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 degrees 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.

Automated summary

Tire wear particles (TWPs), a type of thermosetting microplastic, accumulate in aquatic environments due to their wide use in road traffic. Aging of tire materials due to friction heat can lead to water evaporation, additive volatilization, and polymer decomposition, posing potential risks to ecosystems. This study investigated the pyrolysis behaviors and products of thermally aged tire MPs using a thermogravimetric analyzer coupled with FTIR and GC/MS. The results revealed the main pyrolysis gases and products, and showed changes in the release of compounds with thermal aging. These findings provide new insights into TWP aging evaluation and their fate in aquatic and terrestrial environments.