Understanding the Science Behind How Methylene Chloride/Phenolic Chemical Paint Strippers Remove Coatings

摘要

The objective of this program was to obtain a sound understanding of how methylene chloride/phenol-based (MC/P) paint strippers function by understanding the specific roles of the primary paint stripping components; methylene chloride, phenol, ethanol, and water. This was accomplished through s series of tasks including sample selection, conceptual and computational molecular modeling, infrared spectroscopy, measurements of volume swell, the extent and rate of debonding and the analysis of the solvent absorbed by a model coating system. The results show that methylene chloride serves primarily as a penetrant and as a carrier for the other solvent components. Phenol is also a powerful penetrant, but also serves as a weak organic acid and is the primary active component. However, in order to function efficiently, phenol requires the presence of water which 'activates' the phenol through a reaction forming phenoxy and hydronium ions. Ethanol serves as a co-solvent and increases the solubility of water in the solvent phase. This study has shown that the two most significant functions of a paint stripping solvent are to penetrate the coating to deliver a weak organic acid to the bonding interface. In the near term it suggests that the performance of some alternative paint strippers may be improved by including a weak organic acid. In the long term, this provides a framework to developing new paint removal systems. Specifically, methylene chloride could be eliminated if an alternative means of accessing the bonding interface could be devised. This in turn would allow the use of a weak organic acid other than phenol, resulting in an environmentally acceptable paint stripping method.