THERMOANALYTICAL STUDIES ON NEW POLYMORPHIC FORMS OF PROPYL, OCTYL AND DODECYL GALLATES

The thermal behavior of propyl (PG), octyl (OG) and dodecyl (DG) gallates, three antioxidants widely used in fuel and food industries, was evaluated by thermoanalytical techniques (TG, DTA, DSC and hot stage microscopy), and complementary techniques, such as FTIR-ATR and XRD. All of them presented melting in characteristic temperatures during heating. The resulting liquid phases crystallized in different solid forms when cooled just after melting. However, when the samples were heated beyond melting temperature, they decomposed. Although thermal studies were conducted at higher temperature than those in which they are regularly used, this work provided relevant information regarding their thermal behavior at higher temperatures. Data from XRD, FTIR-ATR and hot stage microscopy were used to confirm the presence of new polymorphs. Finally, based on these results mechanisms describing the thermal behavior of PG, OG and DG were proposed.

Automated summary

The thermal behavior of propyl, octyl, and dodecyl gallates were evaluated using various thermoanalytical techniques, showing characteristic melting behavior and crystallization of different solid forms upon cooling. Beyond the melting temperature, the samples decomposed. The study provided relevant information about their thermal behavior at higher temperatures and proposed mechanisms based on the results of XRD, FTIR-ATR, and hot stage microscopy.