Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2012
Publication Date: 4/16/2012
Citation: Liu, Y., Thibodeaux, D.P., Gamble, G.R., Bauer, P.J., Vanderveer, D. 2012. FT-mid-IR spectroscopic investigation of fiber maturity and crystallinity at single boll level and a comparison with XRD approach. National Cotton Council Beltwide Cotton Conference. p. 1213-1222. Interpretive Summary: Crystallinity index (CI) of cotton fibers has been assessed predominantly by X-ray diffraction (XRD) spectroscopy. It requires 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. 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 FT-mid-IR 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-mid-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-mid-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-mid-IR spectroscopy for rapid, routine, and direct measurement of cotton fiber crystallinity.
Technical Abstract: In previous study, we have reported the development of simple algorithms for determining fiber maturity and crystallinity from Fourier transform (FT) -mid-infrared (IR) measurement. Due to its micro-sampling feature, we were able to assess the fiber maturity and crystallinity at different portions of a single cotton boll, as demonstrated here. Meanwhile, we attempted to compare the fiber maturity and crystallinity information between FT-mid-IR and X-ray diffraction (XRD) measurement. Despite considerable efforts in developing the curve-fitting protocol to evaluate the crystallinity index (CI) from XRD, in its present state XRD measurement 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 measurements. In practice, samples with known CI are very difficult to be prepared or determined. As an approach, we might assign the samples with known CIs from FT-mid-IR procedure. Hence, this study also reported the development of a simple XRD algorithm, over time-consuming and subjective curve-fitting process, for direct determination of cotton cellulose CI by calibrating XRD with the use of CIIR as references.