New strategies to quantify aluminum hydroxide in powder coatings by thermogravimetric analysis and ATR-FT-MIR spectroscopy coupled with chemometrics

Powder coatings industry is a growing trade sector in our days and the process control phase is a critical step with the increasing necessity for rapid methods. In this research, we evaluated the possibility of aluminum hydroxide quantification in powder coatings using thermogravimetric analysis and ATR-FT-MIR spectroscopy. Spiked powder coatings sample standards were realized with a known amount of aluminum hydroxide from 0 to 22% in weight. The thermogravimetric analysis (TGA) was optimized, and the aluminum hydroxide content was determined with a stoichiometric formula based on the delta at the inflection point (DTG curve were derived) in TGA results. The spectroscopic data were acquired, and multivariate regression (Partial Least Squares Regression) was used to model the aluminum hydroxide content with respect to the spectral signal. Models were validated with an external set of real powder coating samples. In this article, a step-by-step model development procedure is illustrated as well as the issues addressed. In addition, models showed the possibility of identifying some additives and resins using only the spectroscopic information.