DC Electrical Conductivity of Cellulose

Abstract

ABSTRACT:DC electrical conductivity was measured from room temperature to about 230°C for Cellulose I and Cellulose II. The conductivity vs. temperature curve showed a break at about l 50°C for Cell I and at about 80°C for Cell II. The break points corresponded to those observed previously in the spacing vs. temperature curves. These phenomena may possibly be assoc-iated with the second order transition at which the restricted motion of chain segments in the crystals begins to acquire high mobility. The conductivity in the fiber axis direction was approximately ten times as large as that in the perpendicular direction.KEY WORDS Cellulose I / Cellulose II / Transition Point / DC Electrical Conductivity / In a previous paper,1 it was found for Cell I (Cellulose I) and Cell II (Cellulose II) that the temperature coefficients of the spacings and intensities of X-ray reflections change discontinuously at l 50°C for Cell I and at I 00°C for Cell II. This suggests that these crystals undergo second order transitions at these temperatures. The present work was undertaken to confirm this, by measuring the de electrical conductivity from room temperature to about 230°C for both Cell I and Cell II. Furthermore, the anisotropy of the de electrical conductivity was studied in the directions of intermolecular and intramolecular hydrogen (chain direction) bonds to observe the effects of hydrogen bonds on the electrical conductivity. EXPERIMENT ALThe samples of Cell I were prepared from softwood tsuga (Tsuga sieboldii CARR) and hardwood kaba (Betula tauschii Kornz), both of which showed clear X-ray meridional reflections. The crystallinities of the untreated samples were almost the same. The samples of Cell II were prepared by measerizing tsuga and kaba with 30% NaOH for 240 h followed by regeneration by washing with cold water. The degree of transformation from Cell I into Cell II was 0.9-1.0, when estimated by Ranby's equation. 2 All the samples were treated with 4N-HC1 at I00°C for 2-lOh to remove any lignin and hemicellulose in the wood.The sample was parallelpiped in form (l0mmx lOmmx 15mm). The arrangement of electrodes and the direction of electric current is illustrated in Figure 1. Stainless steel was used as the electrodes. Silver conducting paste (du Pont Electro-Chemicals Department No. 5504) was spread on both sides of the sample and heated at 200°C for 70 min in order to insure closer contact between the stainless steel and wood.DC electrical conductivity was measured with the de amplifier shown in Figure 2. The maximum applied voltage was 300 V and the standard resistance, I kQ. Prior to each measurement, the specimen was dried at l00°C for about 2h under a pressure of 10-3 torr. RESULTS AND DISCUSSIONThe temperature dependence of the de electrical conductivity a of Cell I (tsuga) hydrolyzed with 4 N-H Cl at I00°C for various hours is shown in Figure 3. Figure 3A is for the fiber direction and Figure 3B, for the direction perpendicular to it. Breaks are seen at temperatures of about l 50°C in both directions, an...

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