Wide-angle X-ray diffraction study of the effect of periodate oxidation and thermal treatment on the structure of cellulose powder

Abstract

Cellulose and periodate oxidised cellulose powders were investigated for any structural changes occurring when subjected to thermal treatment, since their use as fillers in composites involves prolonged exposure to high temperatures. The wide-angle X-ray diffraction peak at 2θ = 22·9° for the oxidised cellulose samples was found to decrease almost proportionately to the degree of oxidation of the starting cellulose. Whereas heat treatment of cellulose powder at 120°, 180° and 240°C for three hours also produces a continual decrease in the crystallinity of the cellulose, heat treatment of periodate oxidised cellulose at 120°, 180° and 240°C for three hours produces drastic changes in the crystallinity of the resultant products. For 16% oxidised cellulose heated at 240°C for three hours, almost total crystallinity is lost. This is also seen from the increase in line broadening of the X-ray diffractogram. An interesting feature in the above cases was the appearance of an additional peak at 2θ ≈ 12°. In DTG studies the temperature at which the major loss in weight (~62%) occurred was ~290°C for most samples. The final weight loss (~85%) generally occurred at 430-450°C. The 16% oxidised cellulose behaved somewhat differently, and reasons for this are explained.