Elevated volatile organic compound emissions from coated thermoplastic polyester elastomer in automotive interior parts: Importance of plastic swelling

Volatile organic compounds (VOCs) in vehicle cabins pose some health concerns, especially in new cars where interior plastics contribute substantially to VOCs emissions. We investigated the reasons for enhanced VOCs emissions from surface-coated thermoplastic polyester elastomer (TPEE), an automotive interior plastic. After applying solvent-based primer and clearcoat coatings, total VOCs (TVOC) level increased by 12.1 times (2066-24,983 mu g m(-3)). Among the 15 emitted VOCs, seven VOCs (esters and ketones) originating from the coating solutions accounted for 77.4 % of TVOC. The remaining solvents resulted from TPEE swelling during coating owing to high chemical affinity with the solvents as evidenced by a low contact angle (14.3 degrees) and high degree swelling (68.9%). Further baking at 80C reduced VOCs levels over time, but some major compounds (methyl isobutyl ketone and butyl acetate) persisted until 6 h. Primer and clearcoat films reduced solvent volatilization by approximately 70 %, creating a blocking effect. Apart from solvents, neat TPEE contained 4.2 % of its weight as potential VOCs. Therefore, enhanced VOCs emissions stem from three factors: (1) excessive TPEE swelling caused by coating solvents and residual solvents released as VOCs, (2) restricted volatilization caused by the coating, and (3) emission of inherent VOCs from neat TPEE.