Samira The sample is heated in a furnace

Samira F. E. et al. (1985) study the thermalbehavior of several chemically modified cellulose samples by thermogravimetricanalysis (TGA) and differential thermal analysis (DTA) techniques.Carboxymethylcellulose (CMC; the sodium salt), BDH grade, the high viscosity of 1500 ± 400 cpfor the 1% aqueoussolution at 20°C with a DS of 0.7-0.8is used in this study.

Thermalgravimetric analysis and differential thermal analysis is performed by using automaticthermobalance. The furnace programmed to increase the temperature by 5oC/minand the heat is continued until a constant weight is attained in a constantstream of air Figure 5 17. Figure 5 TG curve for carboxymethyl cellulose The curve Figure 5 of the sample can be classified into three distinctzones. An initial slight loss in weight is seen due to the evaporation ofwater, then a rather sharp break occurs in each of thermogram, indicating theonset of a decomposition process involving a rapid loss in weight; this breakends with a slight curvature that may bedue to the formation and evaporation of some volatile products. Finally, thedecomposition rate decreases, gradually reaching a constant weight representingcarbonization of the remainder.

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The T1 represents thetemperature at which the main decomposition reaction starts. To measure thethermal stability and decomposition temperature of the sample, straight lines drawnbefore and after the initial sharp break in the curves; the intersect of thesetwo lines (T2)represents the decomposition temperature. From the figure, we note that CMC starts to decompose at265oC 17. Inthermogravimetry, the change in sample mass is measured by a thermobalance as a function of temperature ortime.

The sample is heated in a furnace according to a time-temperatureprogram. This method is routinely used to determine the sample moisturecontent, hydration level, and decomposition temperature. By considering thetemperature range of the weight loss, adsorbed and bound water can bedifferentiated.

The pattern and temperature range of sample decomposition canalso serve as a qualitative tool for compound identification 16.


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