Determination of the vapor pressure curves of adipic acid and triethanolamine using thermogravimetric analysis

The evaporative properties of adipic acid, triethanolamine (TEA), and glycolic acid have been studied by thermal analysis. Samples were heated in a simultaneous thermogravimetric-differential thermal analysis (TG-DTA) unit at 10 degreesC min(-1) in a dry nitrogen atmosphere flowing at 100 mL min(-1). Benzoic acid was used to calculate a calibration constant which could then be inserted into a modified Langmuir equation to calculate vapor pressure curves for adipic acid, TEA, and glycolic acid. The results were compared to vapor pressure curves generated by use of Antoine constants, where these were available. Good correlation was obtained between the two sets of curves for adipic acid and TEA. Glycolic acid decomposed and evaporated in the same temperature range, thus, making calculations invalid. (C) 2004 Elsevier B.V. All rights reserved.