Abstract: The natural polymeric material, gutta-percha, was non-isothermally analyzed by thermogravimetric and differential thermogravimetric techniques at different heating rates of 5, 7.5, 10, 15℃/min under the nitrogen atmosphere. Thermal analysis kinetics methods of multi-heating rate methods (Starink, Kissinger and Flynn-Wall-Ozawa methods) and single heating rate methods (Coats-Redfern and Achar methods) were applied to infer the most probable reaction mechanism and calculate the corresponding kinetic parameters of apparent activation energy E_a and pre-exponential factor A. The results showed that thermal decomposition of gutta-percha began at 268℃ and ended at 459℃ with a complete mass loss. The increasing of heating rates had a significant effect on the decomposition. The TG-DTG curves moved to higher temperatures while a hysteresis effect of thermal decomposition occurred. The most probable thermal decomposition mechanism was Chemical Reaction, corresponding with Reaction Order Equation. The values of apparent activation energy E_a and pre-exponential factor lnA were 191.54 kJ/mol and 33.34, respectively. Compared with other modified natural or synthetic rubbers, characteristic parameters of gutta-percha revealed its strong thermostability while at high temperatures it decomposed fast. Through integral calculation for the differential kinetic equation, the storage time of heat resistance at 200℃ were 170 days.

Key words: gutta-percha, TG-DTG, thermal stability, non-isothermal kinetics, storage time of heat resistance