Location: Cotton Structure and Quality Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop new or improved industry-supported methods to measure moisture in cotton fiber. Sub-objective 1a: Develop and implement accurate reference methods to replace the existing standard oven-drying methods to alleviate the biases in the latter methods. Sub-objective 1b: Develop more accurate techniques to measure the “free” and “bound” water contents in cotton for use in understanding which quality indicator correlates best with the fiber properties. Objective 2: Determine the bases for the interaction of moisture with cotton structures and resulting fiber properties. Sub-objective 2a: Determine the structures and interactions of cotton cellulose crystals and amorphous regions at the molecular level. Sub-objective 2b: Determine the impact of moisture interaction/moisture levels on fiber physical properties and on the transport properties of moisture between cotton fibers. Sub-objective 2c: Improve the understanding of factors that control molecular shape and reactivity for cotton.
1b. Approach (from AD-416):
This research is a comprehensive effort to optimize the measurement of the amount of water in cotton fiber by both reference and rapid, indirect methods, to understand the structural bases for the interaction of water with cotton, to determine the implications of water for cotton performance properties, and to develop means of optimizing the effects of water on cotton performance. The first objective develops a more accurate measure of the water in cotton fiber. Karl Fischer Titration (KFT) and Low Temperature Distillation (LTD) techniques will be used to develop new fiber reference moisture methods. Solvent extraction techniques, followed by the KFT method for moisture, will be used to separate and measure the free water and bound water fractions of the total moisture level. The second objective develops a deeper understanding of fiber structure at the molecular, crystallite, and microfibrillar levels, how water interacts with, and moves within, these entities, and how these levels are affected by water. Theoretical and experimental molecular modeling and X-ray diffraction studies will be used to characterize and establish new structural features. A large number of rapid moisture measurement techniques (chemical, electric, spectroscopy, gravimetric) will be compared to the present oven and new reference moisture methods. Environmentally controlled chambers, in combination with sensors, will be used to monitor moisture transport through a specified mass/density of cotton fiber and to characterize moisture impacts (e.g., strength/ breakage) on cotton fiber by varying the relative humidity and temperature. Light and electron microscopy and molecular spectroscopy will be used to monitor changes in structure and breakage patterns with moisture.
3. Progress Report:
New industry supported methods to measure water in cotton fiber samples are being developed. Difficulty in holding samples at standard testing conditions of 70° Farenheit and 65% relative humidity (RH) was reduced by putting the samples inside an insulated chamber to control temperature and a salt solution in the chamber maintained humidity. Progress was also made by separating the total water content in raw cotton into fractions, such as the water in the botanical trash and the water in the fiber’s cellulose. Mathematical relationships that describe the way that water content is affected by changes in growth, harvesting, and ginning could provide a blueprint to improve those processes. Fifteen moisture measurement instruments and methods were compared to the standard oven and the SRRC-developed Karl Fischer Titration (KFT) reference methods. Moderate-to-very good method agreement results were observed for twelve of the units. A Comparison Matrix was updated to assist selection of the best overall moisture system for their needs. Initially, selected instruments were calibrated to the KFT method. The methods agreed well and the work was expanded to include different temperatures and relative humidities. Initial results at high air moisture (80° Farenheit/75% RH) were unexpected. Each moisture measurement method responded differently to increased temperature and RH. New and replicate evaluations are underway at expanded temperature/RH ranges. The effect of moisture on bundle strength, elongation and fracture morphology of cotton fibers was further examined. Increases of fiber strength and elongation with higher moisture content were confirmed. Infrared microscopy (IR) showed different spectroscopic bands for cotton samples before and after fracture. Electron microscopy showed different fracture morphology for samples broken at different humidity levels. The evolution of spectroscopic bands associated with moisture was observed with IR microscopy on dry cotton webs that were later exposed to water. Also, X-ray diffraction was used to examine the crystallinity (which affects physical properties) of cotton fibers harvested at different days post-anthesis (after flowering) and compared to progression of fiber properties and IR bands. The nature of the nanoparticles that make up most of the cotton cellulose was explored in collaboration with scientists at the Louisiana State University AgCenter. Previously observed, very different self-assembled physical states of freeze-dried nanoparticles made from native and mercerized cotton are hypothesized to result from different concentrations of the particles, leading to ideas of how the fiber structures might be modified in the future. Collaborators in Austria and Japan were assisted by explaining the right-handed twist of a short fragment of normally untwisted or left-handed cellulose that had been chemically modified to have the ability to generate electrical current, allowing the potential of photocell garments. It is because the chemical modifications were applied to the first and third glucose units in the molecule (but not the second) that the structure would be right-handed.