Physicochemical investigation of chemical paint removers. II: Role and mechanism of phenol in the removal of polyurethane coatings

• Simplified polyurethane top-coatings were formulated for study.
• Bulk and molecular-level effects of simplified paint removers were studied.
• Phenol is observed to degrade the coatings by nucleophilic attack.
• Chain scission leads to severe irreversible Tg depression and coating failure.

Thermal and spectroscopic techniques have been used to study the interactions of phenol with model polyurethane coatings. Previous work has pointed to phenol as the principal source of polymer degradation in methylene chloride/phenol paint stripping mixtures. Thermal analysis demonstrates that the addition of phenol leads to severe depression in Tg and outright coating failure. Exposure appears to cause chain scission, leading to significant weight loss during thermal analysis. XPS confirms the deposition of methylcellulose stabilizer at the surface, but also indicates breaches in the conformal coating which we attribute to polyurethane degradation. Raman and ATR-FTIR spectroscopy confirm chemical modification of the polyurethane by phenol, leading to the proposed model of degradation by nucleophilic attack.