TY - THES

T1 - Investigation of water absorption of cellulose fibers by gravimetric analysis and atomic force microscopy

AU - Kreiml, Patrice

N1 - embargoed until null

PY - 2016

Y1 - 2016

N2 - Cellulose fibers are the base for a variety of products in our daily lives, such as paper, construction, textile, hygiene, and medical products. For several of these products, the native cellulose fibers, extracted from wood, are insufficient. Textile, hygiene, and medical products require long fibers, that can be spun into a thread. In the viscose process, native cellulose fibers from pulp are dissolved in a viscose solution and spun into pure viscose fibers. This work is divided into two parts. One part comprises the measurement of water absorption of cellulosic fibers by employing a sorption balance. The term sorption denotes absorption, as well as desorption. The sorption balance in this work recorded the gravimetric uptake and decrease of water vapor at varying water vapor pressure at 17 °C. The obtained sorption isotherms were also used to determine the absorption behavior of the fibers. The samples for the sorption measurements were provided by an industrial collaborator. The samples consisted of three different types of viscose fibers, called Bellini, Verdi, and Danufil, as well as a sample of pulp fibers from a mixture of spruce and pine. Two configurations of sample preparations were employed, one with loose bundles of fibers, and the other one with tightly packed fibers compressed into a wire whisk. In the former, single fiber properties were measured, and the relative water absorption of the different types of viscose fibers was very similar. All viscose fiber samples exhibited a relative water absorption slightly above 20 % and the pulp fiber sample slightly below 20 %. The compressed viscose samples yielded a relative water absorption above 30 %, whereas for the compressed pulp samples it was 26 %. The higher values are thought to be caused by network effects of the tightly packed samples, which is supported by the shape of the isotherms. The other part of this thesis was dedicated to the investigation of viscose fiber surfaces with atomic force microscopy (AFM). The investigated samples comprised two sets of trilobal viscose fibers provided by an industrial supplier. Each set consisted of two batches from the same production line, one set with water absorption capacity above average and the other one with values below average. Under the assumption that the fibers' surfaces contribute significantly to the water uptake, AFM was employed to find a correlation between water uptake and surface features. The analysis of the three roughness parameters RMS-roughness σ, lateral correlation length ξ, and Hurst parameter α yielded no correlation to water absorption. Trenches covering all fiber surfaces were analyzed thoroughly regarding their angle, length, and density. In the end, only the trench density in both sample sets exhibited a possible correlation, where a lower trench density correlated to higher water absorption.

AB - Cellulose fibers are the base for a variety of products in our daily lives, such as paper, construction, textile, hygiene, and medical products. For several of these products, the native cellulose fibers, extracted from wood, are insufficient. Textile, hygiene, and medical products require long fibers, that can be spun into a thread. In the viscose process, native cellulose fibers from pulp are dissolved in a viscose solution and spun into pure viscose fibers. This work is divided into two parts. One part comprises the measurement of water absorption of cellulosic fibers by employing a sorption balance. The term sorption denotes absorption, as well as desorption. The sorption balance in this work recorded the gravimetric uptake and decrease of water vapor at varying water vapor pressure at 17 °C. The obtained sorption isotherms were also used to determine the absorption behavior of the fibers. The samples for the sorption measurements were provided by an industrial collaborator. The samples consisted of three different types of viscose fibers, called Bellini, Verdi, and Danufil, as well as a sample of pulp fibers from a mixture of spruce and pine. Two configurations of sample preparations were employed, one with loose bundles of fibers, and the other one with tightly packed fibers compressed into a wire whisk. In the former, single fiber properties were measured, and the relative water absorption of the different types of viscose fibers was very similar. All viscose fiber samples exhibited a relative water absorption slightly above 20 % and the pulp fiber sample slightly below 20 %. The compressed viscose samples yielded a relative water absorption above 30 %, whereas for the compressed pulp samples it was 26 %. The higher values are thought to be caused by network effects of the tightly packed samples, which is supported by the shape of the isotherms. The other part of this thesis was dedicated to the investigation of viscose fiber surfaces with atomic force microscopy (AFM). The investigated samples comprised two sets of trilobal viscose fibers provided by an industrial supplier. Each set consisted of two batches from the same production line, one set with water absorption capacity above average and the other one with values below average. Under the assumption that the fibers' surfaces contribute significantly to the water uptake, AFM was employed to find a correlation between water uptake and surface features. The analysis of the three roughness parameters RMS-roughness σ, lateral correlation length ξ, and Hurst parameter α yielded no correlation to water absorption. Trenches covering all fiber surfaces were analyzed thoroughly regarding their angle, length, and density. In the end, only the trench density in both sample sets exhibited a possible correlation, where a lower trench density correlated to higher water absorption.

KW - cellulose fibers

KW - AFM

KW - microbalance

KW - sorption balance

KW - native cellulose fibers

KW - pulp fibers

KW - regenerated cellulose fibers

KW - viscose fibers

KW - water absorption

KW - isotherm

KW - roughness

KW - Zellulosefasern

KW - AFM

KW - Mikrowaage

KW - Sorptionswaage

KW - natürliche Zellulosefasern

KW - Zellstofffasern

KW - regenerierte Zellulosefasern

KW - Viskosefasern

KW - Wasserabsorption

KW - Isotherme

KW - Rauigkeit

M3 - Diploma Thesis

ER -