Generally speaking, each cellulose crystallinity (CrI) estimation method has its advantages and limitations which in part depends upon sample characteristics (e.g., composition). In the present investigation, CrIs of H<sub>2</sub>SO<sub>4</sub>-hydrolysis produced CNCs from wood (W), bleached kraft-pulp (BKP), cotton microcrystalline cellulose (MCC), bacterial cellulose (BC), tunicate (T), and cladophora cellulose (CC) were investigated using 380-Raman, solid state NMR, and XRD methods. In the case of CNCs, because the samples consisted of mostly cellulose, the analysis from any of these methods was thought to be equally reliable. However, the CrI ranking orders generated by these methods were not equivalent. High to low CrI order by 380-Raman method was, BC = MCC &gt; CC &gt;T &gt; W &gt; BKP. In contrast, similar rankings of CrIs by NMR and XRD were, respectively, CC &gt; T &gt; BC &gt; MCC &gt; W &gt; BKP and BC ≥ MCC ≥ T &gt; CC ≥ W &gt; BKP. This suggested that, at least for the high CrI CNCs, the crystallinity order depended on the method used to estimate the CrIs. Currently, the reasons for this are not clear. Nevertheless, irrespective of the method used, the lowest-but-one and lowest CrIs were obtained for W and BKP CNCs, respectively. To further investigate if presence of water in the CNCs had any impact, CrIs of wet CNCs were analyzed by Raman and NMR. In the wet state, the rankings were CC &gt; BC ≥ T &gt; MCC &gt; W &gt; BKP and CC &gt; T &gt; BC &gt; MCC &gt; W &gt; BKP by 380-Raman and NMR, respectively. This indicated that while in the wet state NMR retained the dry-order, this was not the case in 380-Raman. Moreover, in both the methods, the absolute CrI values in wet and dry states differed. In addition to the CrI information on the CNCs, such information on the feedstocks from which the CNCs were produced will be discussed.

Comparing crystallinities of CNCs by Raman, NMR, and XRD

253rd National Meeting (2017)

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