Submitted to: Journal of Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2012
Publication Date: August 3, 2012
Citation: Liu, Y., Thibodeaux, D., Gamble, G.R., Bauer, P.J., Vanderveer, D. 2012. Comparative investigation of Fourier Transform Infrared (FT-IR) spectroscopy and X-ray Diffraction (XRD) in the determination of cotton fiber crystallinity. Journal of Applied Spectroscopy. 66(8):983-986. Interpretive Summary: X-ray diffraction (XRD) spectroscopy has been frequently used to determine crystallinity index (CI) of cotton fibers. It requires a computing software to separate amorphous and crystalline contributions through a time-consuming and subjective curve-fitting process. In general, XRD provides a qualitative or semi-quantitative evaluation of CI readings. To generate a reliable quantitative cellulose CI, it should have appropriate cellulose standards to calibrate or validate the XRD measurement. Apparently, these absolute standards are not easy to be prepared or determined. In the latest Fourier transform infrared (FT-IR) spectroscopy investigation on immature and mature cotton fibers, we proposed a ratio algorithm R2 by linking it with the relative amount of Iß to Ia crystal forms, which yielded an overall 96% of correct classification accuracy. This study first developed the simple algorithms from XRD spectra, and then demonstrated the effectiveness of both FT-IR and XRD techniques in describing the structural changes of developing cottons at single boll level. In addition, it reported the strategy of applying easy- and fast- determinable CI from FT-IR acquisition to calibrate the XRD measurement for cellulose CI. This proposal provides agricultural engineers, cotton fiber and cellulose researchers a new sight in applying FT-IR spectroscopy for rapid, routine, and direct measurement of cotton fiber crystallinity.
Technical Abstract: Despite considerable efforts in developing the curve-fitting protocol to evaluate the crystallinity index (CI) from the X-ray diffraction (XRD) measurement, in its present state XRD procedure can only provide a qualitative or semi-quantitative assessment of the amounts of crystalline or amorphous portion in a sample. The greatest barrier to establish quantitative XRD is the lack of appropriate cellulose standards needed to calibrate the XRD measurements. In practice, samples with known CI are very difficult to be prepared or determined. In a previous study (Textile Research J., 81, 1559 (2011)), we reported the development of simple algorithm for determining fiber crystallinity information from Fourier transform-infrared (FT-IR) spectroscopy. Hence, in this study we not only compared the fiber crystallinity information between FT-IR and XRD measurements, by developing a simple XRD algorithm over time-consuming and subjective curve-fitting process, but also suggested a direct way of determining cotton cellulose CI by calibrating XRD with the use of CIIR as references.