OVERVIEW ON NATIVE CELLULOSE AND MICROCRYSTALLINE CELLULOSE I STRUCTURE STUDIED BY X-RAY DIFFRACTION (WAXD): COMPARISON BETWEEN MEASUREMENT TECHNIQUES

Abstract

The crystalline structure of cellulose has been studied for a long time. It is well known that crystallinity of cellulose can be measured using quite a number of methods, X-ray diffraction, solid state 13 C CP-MAS NMR, Fourier transforminfrared (FT-IR) spectroscopy and Raman spectroscopy. The solid state 13 C CP-MAS NMR and FT-IR spectroscopy considers contributions from both crystalline and non-crystalline cellulose regions resulting in relative values, while the alternative X-ray diffraction approach gives more detailed data on features of crystalline and less on the non-crystalline fraction of cellulose. Raman spectroscopy is also used to study cellulose crystallinity. This paper gives an overview on the crystallinity of three cellulose samples, cotton linters, microcrystalline cellulose (cotton linters) and Avicel powder cellulose (Avicel PH101) determined by wide angle X-ray diffraction (WAXD). The study compares literature data with our data for the apparent crystallinity (%) of the mentioned samples from different sources to demonstrate the dissimilarities that can be obtained using different X-ray methods. For the crystallinity analysis, assumption had to be made that all cotton linters and Avicel PH-101 used in the literature were of the same quality, even though it has been reported that the quality of both samples can vary between batches and production locations. The reported crystallinity values of cotton linters were between 56-78 %, for microcrystalline cellulose (MCC), crystallinity varied within the range 65-83 % and Avicel PH-101 powder gave crystallinity values between 37-93 % dependent on the Xray methods and experimental mode used.