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title(En) :Chemorheology of Wood. III. Diffusion Controlled Stress Relaxation in Wood
author(En) :Tsutomu Aoki, Tadashi Yamada
information :Mokuzai Gakkaishi 24(6), 380-384 (1978)
assort :Original Article
summary(En) :   The diffusion controlled torsional stress relaxation for untreated Hinoki and Hinoki treated with DMSO and the DEA-SO2-DMSO mixture was investigated and the following results were obtained.
   1) Two relaxation processes were observed in wet and DMSO swollen conditions. The values of activation energy Eact in these processes were 23.7 kcal/mole (Physical Relaxation I) and 21.6 kcal/mole (Physical Relaxation II), respectively. It was considered that physical relaxation I would result from a molecular motion in the amorphous region of both cellulose and hemicellulose, while physical relaxation II from that of lignin. On the other hand, in the diffusion controlled process of Hinoki which was initially in dry condition, these Eact values decreased to about one-half.
   2) A relaxation process (Physical Relaxation D) occurred in the diffusion controlled relaxation of Hinoki which was initially in dry condition and its Eact value was 12.4 kcal/mole. It was suggested that it would be due to changes in the microstructure such as inter- and intra-molecular networks. In the diffusion controlled relaxation, the value of chemical relaxation of Hinoki which was initially in dry condition was almost equal to those of physical relaxation I, II and D.
   3) The Eact value of the chemical relaxation process in sulfuric acid solution for Hinoki which was initially in wet condition was about 1/2-1/3 of that obtained from the measurements of viscosity and weight loss under the homogeneous reaction. On the other hand, those of Hinoki which was initially in DMSO swollen condition and treated with the DEA-SO2-DMSO mixture were 28.5 kcal/mole and 34.7 kcal/mole, respectively, and these values were almost equivalent to those obtained under the homogeneous chemical reaction. In this connection, it may be suggested that the values of 28.5 kcal/mole and 34.7 kcal/mole correspond to the activation energies due to the scission of a glucosidic bond in amorphous region and in crystalline region of cellulose treated with DEA-SO2, respectively.