It clearly shows that the onset, maximum peakdegradation temperatures, moss loss at Tmax and maximumdegradation rate are increased in a linear fashion as the heating rates (?).This temperature shift might be due to heat transfer effect. On the other hand,the residual char yield decreased as the heating rate increased might be due torapid pyrolysis, which needs very high heating rate and short residence timefor the degraded products. However, there is no significant difference in theonset and maximum peak degradation temperatures of NaCMC. Case study 4Ge Y.
et al. (2013) study on thefeasibility of preparing cellulose from sugarcane bagasse its structurecharacterized by means of TGA. TGA measurements areperformed in an instrument STA449C (Netzsch) using 8?10 mg of powder sample in sealed aluminum crucibles under nitrogen flow(20 ml/min) and heated from 25oCto 600?C at 15oC/min. A smallmass loss is found for NaCMC1 in the range of 50-150 oC due to theevaporation of the humidity of the materials or low molecular mass compoundsremaining from the chemical procedures. Furthermore, decomposition of cellulosehas a sharp mass loss at 350 oC, and it is almost decomposed to a residualmass of 20%. On the other hand, the decomposition of NaCMC1 starts around 250oC and it has a higher residual mass of 50%. The differences in thestarting temperature for degradation imply that NaCMC1 had a lower thermalstability than that of cellulose, which can be due to a higher degree of orderof NaCMC1 and a less quantity of intermolecular hydrogen bondings compared tosource cellulose that is certified by IR spectroscopy.
The differences in residual mass are caused by thehigher DS and molecular mass of NaCMC1 that can enhance the char-formingability 26. Akram M.et al.
(2016),perform TGA ramp test to determine themain procedures of weight loss occurring during the thermal degradation of CMCand their respective temperatures. Results confirm the preliminary findingsmade by DSC. The first step is observed between 40 and 200 oCand is attributed to the loss of moisture content, additionallyconfirmed by the results of isothermal TG analysis at 100 oCfor 60 min. The onset of decomposition takes place at 242 oC,reaching its maximum rate at around 265 oC,before termination at 305 oC.At the point of the highest degradation rate,the sample will have lost 36.3 % of its initial weight. This weight loss isattributed to the decarboxylation of CMC, releasing CO2, in additionto the loss of hydrogen and oxygen molecules due to the splitting off ofvarious side groups.
By the end of the main decomposition stage, the CMC sample under investigation haslost around 50 % of its initial weight. The furthermass loss is observed as the temperature was raised up to 500 oC,albeit at a much lower rate, leaving behind an ash content of 41 %. Applyingrate-controlled mass change conditions pinpoints the decomposition temperatureat 269 oC, where the major weightloss stage can be clearly identified. Isothermal TG soaking tests are performedto evaluate the time needed for CMC decomposition under various isothermallyheld conditions.
As the temperature isincreased from 260 to 300 oCthe decomposition time decreases from 26 to 12 min. After this period, thedecomposition reaction is complete, beyond which no further weight loss isobserved.