An application of TGA technique to elucidate the chain reaction mechanism of cellulose pyrolysis is discussed. The mathematical expressions for isothermal kinetics are modified for use with temperature‐programmed kinetics. It is shown that in temperature‐programmed kinetics, the initial reaction should theoretically be a pseudo zero‐order type, whereas the latter part should be a pseudo first‐order type. Experimental data from the present study and from the literature are in good agreement with the theory. Energies of activation for the initiation and the propagation steps of cellulose pyrolytic reactions are analyzed from TG data. Various cellulose samples, such as adsorbent cotton, vibratory ball‐milled absorbent cotton, mercerized commercial yarn, mercerized and treated commercial yarn, dewaxed‐kiered cotton, and microcrystalline cellulose are included in this study. A basic problem which is associated with all thermogravimetric kinetic expressions is also discussed.

An easier technique for the determination of reaction constants such as order, energy of activation, and frequency factor from the thermogravimetric data has been described. The method requires two TGA curves obtained with different sample weights under similar reaction conditions. Applicability of the method to complex reactions, where simultaneous decomposition occurs, has been discussed. Reaction constants for different steps of the decomposition of calcium oxalate monohydrate are evaluated.