Can Cellulose Crystallinity Be Accurately Measured?
Although measurements of crystallinity index (CI) have a long history, it has been found that CI varies significantly depending on the choice of measurement methodology. In this study, the concept and measurement techniques of crystallinity index were investigated using five different methods from x-ray diffraction and solid-state 13C NMR. It was found that the most popular and simple method, using measurement of just two heights in the x-ray diffractogram, produced significantly higher crystallinity values than did the other methods. Data in the literature and our experimental results support this observation. The analysis of CI measurement becomes complicated when biomass samples are used due to the amorphous contribution from hemicellulose and lignin. New method with sum frequency generation vibration spectroscopy will be introduced, which can selectively analyze cellulose structure without any interference from amorphous components.
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