A salicylic acid-guanidine-formaldehyde (SGF) tercopolymer was synthesized by the condensation of salicylic acid with guanidine carbonate and formaldehyde in 1 : 1 : 2 molar proportions in the presence of 2M HCl as a catalyst. The SGF tercopolymer was characterized on the basis of elemental analysis and ultraviolet-visible, IR, and NMR spectral studies. The Freeman-Carroll and Sharp-Wentworth methods were used to calculate the activation energy and thermal stability of the tercopolymer. Kinetic parameters such as activation energy, entropy change, free-energy change, frequency factor, apparent entropy change, and order of reaction were calculated with the Freeman-Carroll method. (C) 2004 Wiley Periodicals, Inc.