| summary(En) : | The viscosity and the weight of linter cellulose isothermally heated in vacuo were measured to study the early stage of the pyrolysis.
The number average degree of polymerization (DP) of the cellulose, which was rapidly lowered at first, attained to the leveling off value of about 100. The decrease in the DP is explained by means of a chain mechanism of random-scission initiation and grafting or cross-linking termination. The activation energies and the pre-exponential factors for the random scission and the termination are 38.0 kcal/mole and 1.4×1010 sec-1, and 31.4 kcal/mole and 2.9×109 sec-1, respectively. Those for the propagation, which is supposed to determine the weight loss by producing volatile levoglucosan, are estimated to be 31.5 kcal/mole and 8.9×109 sec-1 on the basis of the above values and the Arrhenius parameters for the weight loss.
According to the proposed mechanism, the leveling off of the DP means a stationary state between the initiation and the termination. However, there is another possibility that it corresponds to the crystallite length. |
22040238.pdf