The objective of this project was to further investigate the relationship between cotton cellulose’s crystalline structure and the fibre’s tensile properties, as affected by chemical, genetic and/or environmental effects. In the end, because of time constraints, the variation in tensile properties as a result of these effects was not explored. Instead a select, well described group of fibre samples, controlled for micronaire, but with a wide range of tensile properties, in particular elongation, was selected for examination.

Whilst the application of IR spectroscopy and X-ray diffraction (XRD) to analyse the structure of cellulose is not new, this study utilised techniques not previously applied in the examination of cotton’s crystallite structure. These included the application of the Australian Synchrotron SAXS/WAX beamline to aligned arrays of single mature and immature fibres and the use of a confocal micro-Raman microscope with a polarizing lens to identify and measure different areas within single fibres. More routine measurements of fibre bundles using Fourier Transform Infrared Attenuated Transmission Reflectance (FTIR-ATR) and Raman spectroscopy were also made.

This project has identified new analytical techniques to survey the structural properties of single cotton fibres. Investigations using these techniques revealed that the cellulose unit cell ‘a’ and 002 lattice dimensions correlate closely with fibre tenacity and elongation as measured by Favimat, and that the 040 and 101 lattice dimensions correlate closely with fibre maturity as measured by Cottonscope. The clarity of these relationships was clear and surprising given that work by other researchers has previously not been able to separate mature, commercial samples on the basis of these structural properties.

Further survey work is required to confirm these relationships. Understanding the extent and variation of these structural properties in new cultivars and in relation to the biochemistry and genetics driving maturation of the cotton fibre cell wall will be important in developing better quality cotton fibre, particularly in terms of tenacity (strength) and elongation.