Simultaneous Analysis of Formaldehyde and Methanol Emissions During Curing Reactions of Polyester-melamine Coatings

Abstract

This paper introduces a new derivatization agent for the simultaneous quantification of formaldehyde and methanol during curing reactions of complex organic coatings. Formaldehyde emitted from a polyester-melamine coating is derivatized in a gas phase reaction with unsymmetrical dimethylhydrazine (UDMH) to form formaldehyde dimethylhydrazone (FDMH). UDMH and FDMH tend to degrade at temperatures above 200 °C rather fast. The applicability of derivatization agent and analyte as well as their degradation products are therefore discussed thoroughly. In this method curing temperatures of 150 °C with incubation times between 0.1 and 60 min are used to trigger crosslinking reactions. The emissions of formaldehyde and methanol are continuously quantified with headspace gas chromatography to obtain an emission trend. While one of the main sources of formaldehyde is the demethylolation during crosslinking, methanol is produced via hexamethoxymethylmelamine (HMMM) deetherification and as a condensation byproduct. The emission monitoring shows a high potential for comparative and mechanistic investigations. Results show good repeatability with low standard deviations (< 7%) with a quantification limit of 2.09 µg for formaldehyde and 2.08 µg for methanol.