Cotton Fiber Properties: Relative Humidity and Its Effect on Flat Bundle Strength, Elongation, and Fracture Morphology

The effects of the relative humidity (RH) of testing conditions on stelometer cotton flat bundle strength and elongation measurements, and on the morphology of fiber fractures will be discussed in this talk. We observed a trend for stelometer strength and elongations measurements. Testing in conditions with higher RH generally resulted in higher strength and elongation values. The morphology of broken fibers was also affected by the RH of the testing conditions. Fibers broken at high RH (i.e., 71 ± 2°F and 80 ± 2% RH) showed a more frayed fracture where microfibrils were evident; a fracture pattern that suggests independent microfibril failure. In contrast, at standard conditions (i.e., 70 ± 2°F and 65 ± 2% ) fiber fractures were more granular (clean fractures), a reflection of a more unilateral breaking action. At low RH (i.e., 67 ± 2°F and 50 ± 2%), fiber fractures exhibited a distorted granular pattern, with more persistent surface damage that extended well beyond the fracture location. Our findings are of relevance to post-harvest moisture control efforts currently employed in industry, and may contribute to larger efforts to understand the effects of moisture (RH) on cotton fiber properties.