Sisal fibers were modified using silane coupling agents to determine the mechanism of the chemical reaction between the fiber and silane. A combination of scanning electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), and TG/mass spectrometry (TG/MS) were used to investigate the effects of chemical treatment on sisal fibers systemically. The results showed that a layer of film was formed on the fiber surface by silane adsorption. The layer consisted of siloxane and polysiloxane. FTIR spectroscopy indicated that chemical bonds were formed between the silane coupling agent and the fiber. It was further verified by TG-DSC and TG/MS analysis that the decomposition properties of the sisal fibers were changed by the formation of chemical bonds between the silane and the sisal fiber surface. (C) 2013 Elsevier B.V. All rights reserved.