Production of Paper Substrates with Well-Defined Pore Structure and Unidirectionally oriented Fibers

With respect to its macroscopic properties, (e.g., the color, the roughness or the tensile strength), paper is well understood and in general for applications such as graphical paper or packaging, the relationships between the relevant properties and the raw material structure and/or process parameters are known today. However, many of these known relationships are currently based on empirical data. There are approaches, e.g. to describe the influence of the strength of fibers on the strength of paper, but their scope is highly limited.

A major reason for this knowledge gap concerns the structural complexity of paper, which is produced of different plant fibers and thus already intrinsically complex primary building-blocks with a broad spectrum of properties. In addition, there are various natural and synthetic polymers and inorganic materials blended as additives or fillers into the paper sheet during production to achieve certain product performances, which further increases complexity of the paper sheets.

Within this research project, the fundamental understanding of the relationship between macroscopic paper properties and the process parameters in papermaking as well as the microscopic properties examined in the other subprojects will be expanded for novel (functionalized) papers as well as paper-derived inorganic materials. For this purpose, methods are used and further developed in order to systematically change properties such as fiber length, intensity of fibrillation and the degree of fiber orientation during sheet formation with the aim to identify and understand structure-property correlations. In particular, the development of a sheet forming method for highly oriented nonwovens will help to control the orientation of pores in two dimensions.

Future work will then transfer this knowledge onto advanced research questions tackling the fluid-dynamics in paper. Based on these first set of experiments, scheduled for the first 3 years of the project, in a subsequent funding period, the work will be extended to defined production of a three-dimensional sheet structure and its characterization. The latter can include e.g. multilayer paper structures with different properties in the different sheet layers or fiber structure with three-dimensional channels or defined pore systems.