3.5. Thermal analysisThe thermal properties of acetylated and native CNF samplesare illustrated in Fig. 4. The TGA curves of both samples can be dis-tinctly divided into three stages. During the initial stage from roomtemperature to 120◦C, the TGA thermogram of non-acetylated CNFdisplayed a minor weight loss, which is attributed to water desorp-tion. However, this minor loss of weight is not obvious for theacetylated sample; that is to say, the acetylated samples are morehydrophobic than the native CNF. In the second stage, from 220to 390◦C, the crystalline region started to be destructed and thepolymer simultaneously decomposed, which evidently resulted inincrease in amorphous structure and decrease in the degree of poly-merization (Hu et al., 2011). During the third stage, from 390 to600◦C, the crystalline region was completely destructed and thecellulose decomposed into monomer of D-glucopyranose, whichcould be further decomposed into free radicals (Yang, Xu, Ma, &Wang, 2008). The acetylated and non-acetylated nanofibers startto degrade at 300 and 290◦C, respectively, while the main degra-dation peaks for the acetylated and non-acetylated nanofibers werefound to be 360 and 340◦C. In this case, the main degradation can