Interpretive Summary: It is well known that cotton fibers instantly change their moisture content by interacting with the water moisture in their surrounding atmosphere. As water moisture content in the fibers changes, several physical properties of the fiber are significantly affected. In this study, the effects of relative humidity (RH), a factor that affects the atmospheric moisture content, on the strength and elongation of cotton fibers, and on the appearance of fiber breaks were investigated. Stelometer tests performed in conditions with higher RH generally resulted in higher strength and elongation values. The appearance of broken fibers was also affected by 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. In contrast, at standard conditions (i.e. 70 ± 2°F and 65 ± 2% RH) fiber fractures were more even. These findings are of relevance to moisture control efforts currently employed in industry, and they may lead to a better understanding of the effects of breaks and fiber damage on cotton fiber properties.

Technical Abstract:
It is well known that cotton fibers readily exchange moisture content with their surrounding atmosphere. As moisture exchange progresses, several physical properties of the fiber are significantly affected. In this study, the effects of relative humidity (RH), a factor that affects the atmospheric moisture content, on cotton bundle strength and elongation measurements, and on fiber fracture morphology were investigated. Stelometer tests performed in conditions with higher RH generally resulted in higher strength and elongation values. The morphology of broken fibers was also affected by 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. In contrast, at standard conditions (i.e. 70 ± 2°F and 65 ± 2% RH) fiber fractures were more granular. These findings are of relevance to moisture control efforts currently employed in industry, and they may lead to a better understanding of the effects of fractures and damage on cotton fiber properties.