Professor Keller’s Presentation is available online

Investigating the Complex Structure of Low Density Fibrous Webs Using X-Radiographic and Micro-Compression Techniques

Dr. Steven Keller, Miami University

Presentation is (here)

As compared to communication papers, the fibrous structure of paper tissues and towels and nonwovens is typically far more complex. The stochastic distribution of fibers present in the formed web undergoes controlled disruption and rearrangement as processes are used to impart flexibility, softness and absorptivity in the final product. Unlike communication papers that value spatial uniformity of the structural properties (such as grammage, thickness, density and mean fiber orientation) tissues, towels and nonwovens benefit from induced structures such as creping, embossing and drying features, that create non-uniformities in select ranges of scale. In as such, the bulk properties of softness, strength and absorptivity measured in the 10-1 meter scale range are determined by distributed structural characteristics between 10-2 to 10-6 meters. It is also important to consider the induced structures, such as creping lines; through air dried (TAD) features and embossed patterns do not act in isolation but are superimposed on the structure formed in each of the preceding process steps. Thus the rearrangement of fibers in all three dimensions depends on the extent of interfiber bonding and fiber flexibility as well as the forces imparted in deformation.
This presentation provides an overview of the most recent techniques developed in our laboratory to study low density fibrous webs, and the novel analytical approaches for structural characterization. The positioning and orientation of fibers within the structure are determined using 3D X-Ray μ-CTomographic imaging and 2D X-Radiography. Two and three dimensional data sets were used to elucidate the nature of the local structure, including spatially dependent thickness, density and fiber orientation. These structural properties were further applied to the ancillary study of micro-compressibility and feature collapse to develop relationships between web structure and local mechanical behavior.


D. Steven Keller has been an Associate Professor in the Department of Chemical and Paper Engineering at Miami University in Oxford, Ohio, since 2006. From 1996 to 2006 he was on the faculty of the Department of Paper Science and Engineering at SUNY College of Environmental Science and Forestry and a group leader at the Empire State Paper Research Institute in Syracuse, NY. Before that, he worked as a researcher at ESPRI and as a research chemist in the coal and oil industries. Dr. Keller received his B.S. in Chemistry from Syracuse University in 1980, and his Ph.D in Paper Physics from SUNY-ESF in 1996.
Dr. Keller’s research is currently focused on the investigation of the heterogeneity of surface chemistry and distribution of materials within fibrous web structures, inter-structural bonding and the impact that these have on the properties and performance of paper, tissue and towel, and nonwoven products. His current specialization is in characterizing structural properties, such as formation and surface topography, and distribution of apparent density, through mathematical analyses that quantify non-uniformities. This has led to the recent development of new methods for mapping thickness of thin structures, space-scale spectral analysis of material distribution, and methods for assessments of the manufacturing processes that contribute to the final material structure. He is a member of the International Paper Physics community, TAPPI, ACS, IASPM, Sigma Xi, Society of Rheology, Society of Plastic Engineers and the Fiber Society.