Biodiesel is commonly derived from various feedstocks through transesterification. Since thermal degradation is concerned with a lot of scientific applications, it is essential to evaluate the thermal degradation characteristics for biodiesel. In this study, thermal degradation of biodiesel is investigated through thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy (FTIR). The fatty acid composition and the characteristic functional groups of biodiesel are detected by gas chromatography (GC) and FTIR in advance. Then. TGA experiments are conducted at linear heating rates from 20 degrees C min(-1) to 40 degrees C min(-1) under nitrogen atmosphere in temperature range from 25 degrees C to 600 degrees C. Subsequently, the activation energy, including enthalpy, is determined by Friedman method and Flynn-WaII-Ozawa method and the reaction order is calculated through the Avrami theory. In addition, the pre-exponential factor, the Gibbs free energy, and the entropy are also calculated. Finally, to obtain a comprehensive understanding for thermal degradation of biodiesels, all evolved products are detected by FTIR in real time. (C) 2015 Elsevier Ltd. All rights reserved.