INFLUENCE OF STRUCTURE AND MOISTURE ON COTTON FIBER PROPERTIES
Location: Cotton Structure and Quality Research
Title: Preliminary assestment of lint cotton water content in gin-drying temperature studies
Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 4, 2012
Publication Date: December 4, 2012
Citation: Von Hoven, T.M., Montalvo Jr, J.G., Byler, R.K. 2012. Preliminary assestment of lint cotton water content in gin-drying temperature studies. Journal of Cotton Science. 16:282-292.
Interpretive Summary: Moisture is a critical measurement that dictates cotton fiber quality in the ginning process. Measurements of cotton fiber moisture can be expressed in two distinct ways. Moisture content refers to the total weight loss by oven-drying and is expressed as a percentage of moist material. This can include aqueous and non aqueous volatiles as well as water in a test specimen, thus not specific to water. Total water content, as measured by Karl Fischer Titration (KFT) is specific to the total amount of water, both free and bound, in a sample. Because of its specificity to water, KFT, utilizing an inert carrier gas directed into a sealed and heated sample vial, is a more accurate and precise method than moisture content by standard oven drying. In this research study, five cultivars experienced low and high gin-drying temperatures, with moisture measurement determined comprehensively the by both oven moisture and KFT total water contents. Ginned Mississippi Delta cottons, from the same crop year and same gin were further processed to produce mechanically cleaned and scoured and bleached fibers. The samples were grouped by cultivar in order to critically examine the results at moisture equilibrium. Moisture contents were less consistent within and between cultivars than the corresponding total water content values. Normalizing the data provided a pathway to show that by scouring and bleaching the fibers, proper conditioning to moisture equilibrium, and measuring total water content rather than moisture content, results were constant within cultivars, independent of micronaire and gin-drying temperature. .Moisture content by standard oven drying produced biased data relative to the total water results. The bias was persistent in the two fiber matrices compared: raw and mechanically cleaned.
Prior studies to measure total water (free and bound) in lint cotton by Karl Fischer Titration showed the method is more accurate and precise than moisture content by standard oven drying. The objective of the current study was to compare the moisture and total water contents from five cultivars defoliated at different times, and ginned at low and high gin-drying temperature. Ginned Mississippi Delta cottons, from the same crop year and gin, were further processed to produce mechanically cleaned, and scoured and bleached fibbers. The samples were grouped by cultivar in order to critically examine the results at moisture equilibrium. The grand means across all samples analyzed were (%): moisture content – raw (at the gin), raw (at SRRC), and mechanically cleaned, 4.62, 7.42, and 7.30; and total water content – raw, mechanically cleaned, and scoured and bleached, 7.83, 7.69 and 8.10. Within cultivar total water content range of the averaged values from the various treatments was only (%): raw, mechanically cleaned, and scoured and bleached, 0.19, 0.13, and 0.08. These ranges were much smaller compared to those for moisture content. The pathway in this study to produce constant total water content within a cultivar – independent of defoliation date and gin-drying temperature – is to clean sample sets by scouring and bleaching, equilibrate to moisture equilibrium with an aqueous salt solution to control relative humidity, and analyze by Karl Fischer Titration. Under this regimen, the averaged water content was not significantly different within all five cultivars (p > 0.08: 0.083, 0.185, 0.355, 0.372 and 0.535).