## 3 Results and Discussion
### TGA/DTG Analysis  
TGA and DTG curves for the MCC and CNCs samples are displayed in (Figure 9a,b) below. Two distinct stages of rapid weight reduction are depicted in the diagram. Due to their hydrophilic nature, MCC and CNCs samples lost the most weight between 25 and 100 degrees Celsius, with respective losses of 6.09% and 4.78% [46]. When compared to MCCs made from raw materials, CNCs lost the least amount of weight due to water. This coincided with the point that the CNC crystal content peaked. This is in accordance with the XRD results we looked at earlier. Between 289 and 388 degrees Celsius, cellulose depolymerization occurred, causing a loss of weight of 89.89% and 85.88%, respectively [47]. This process was responsible for the release of volatile hydrocarbons and CO\({}_{2}\) emissions. In keeping with these results, [PERSON] [48] reported that between 289 and 388 degrees Celsius, MCC experienced much greater weight loss than NCC.  
Compared to the CNCs sample, which reached its maximum breakdown temperature at 363 \({}^{\circ}\)C, the MCC sample reached 373 \({}^{\circ}\)C. Sulfate (residual H\({}_{2}\)SO\({}_{4}\)) adsorbed on the outer surfaces of cellulose hydroxyl crystals increases the reactivity of the material with increasing temperature, causing the decomposition of CNCs chains at low temperatures, which could account for the lower thermal stability of the CNCs sample compared to the MCC sample [34]. Thus, sulfate content is one of the factors affecting the thermal stability of prepared CNCs.  
Figure 9b, displays the DTG curve for the CNCs sample, which reveals two separate deterioration stages: the first, corresponding to moisture evaporation loss, and the second, attributable to cellulose disintegration approximately 310-380 \({}^{\circ}\)C. As [PERSON] and [PERSON] [49] revealed, sulfate groups on the surface of CNCs sample contribute to the material's thermal instability, so our finding is in line with their findings.  
Meanwhile, residues post-TGA tests were 4.02% and 9.34% for the MCC and CNCs samples, respectively. The greater residue of the CNCs sample may be due to the sulfate groups on the CNCs surface, which tend to promote the CNCs thermal degradation and remain as residue after the thermal analysis under nitrogen [5]. Moreover, the higher residue of CNCs could be due to the higher crystallinity of nanocellulose [50].  
The TGA-activation energy (\(E_{a}\)) was quantified using the Horowitz and Metzger connection in Equation (8) in order to investigate the kinetics of the solid-state decomposition of the MCC and CNCs samples [51].  
\[Ln\left[ln\left[\frac{W_{O}}{W_{T}}\right]\right]=\frac{E_{a}\theta}{RT_{s}^{ 2}} \tag{8}\]  
where \(W_{o}\) is the starting mass, \(W_{T}\) is the mass after heating to temperature \(T\), \(T_{s}\) is the temperature at which 37.202% of the mass has been lost, is the difference between \(T\) and \(T_{s}\), and \(R\) is the gas constant.  
Activation energies for MCC and CNCs samples were calculated to be 101 and 105 kJ/mol, respectively, using Equation (8). Activation energy was seen to rise with decreasing particle size, most likely as a result of the crystalline structural shift that occurs during acid hydrolysis [52]. Moreover, compared to the MCC sample, CNCs are more crystalline. To put it another way, as particle size was reduced to nanometers, surface area was increased, allowing thermal deterioration to occur at lower temperatures [53]. When compared to the XRD pattern, this result is consistent, indicating that crystalline CNCs have indeed formed.