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Abstract: Printability of functional inks on multilayer curtain coated substrates was investigated. The inks represent those commonly used to produce solution processable electronic devices, such as organic transistors. The substrate, which combines sufficient barrier and printability properties for printed functional devices, was manufactured utilizing high speed curtain coating technique. The coating structure consists of a mineral pigment layer coated on top of a barrier layer. The combination of the two layers allows for controlling the absorption of ink solvents. By adjusting the thickness, porosity and surface energy of the top-coating the printability can be tuned for various functional inks. Focus was set on printing conducting silver and carbon inks, both with nano- and micrometer sized particles, as well as printing of an organic semiconductor, poly(3-hexylthiophene). The pore volume in the top-coating determined the spreading of the micrometer sized silver ink as well as the amount semiconductor per area required, whereas the pore size was the determining factor regarding penetration of the nano-sized silver ink. As a proof of concept hygroscopic insulator field effect transistors were printed on the multi-layer curtain coated paper using a custom-built roll to roll hybrid printer. [Copyright &y& Elsevier]

Abstract: In this work, recycled cellulose pulp was dried in a convective dryer and at natural environment conditions. Physical properties of the paper (moisture content, grammage, thickness, apparent and absolute densities, porosity, stretch, tension and burst resistances, dimensional stability and water absorption) were determined and the influence of the drying air temperature and velocity on the final quality of the dried paper, concerning these properties, was analyzed and compared to the paper dried at natural environment conditions. Optical and scanning electronic microscopy was employed to analyze structural changes on the paper surface after drying. The increase of both variables (temperature and air velocity) enhances the drying rates, but is harmful to the quality of the paper, leading to a final product with less uniformity and over-dried surface. [Copyright &y& Elsevier]

The present study investigates two models—two limiting cases—for the internal heat and mass transfer in a multicylinder dryer: the first model assumes that complete redistribution of heat and moisture in the thickness direction occurs instantaneously. The second model assumes that moisture transfer occurs only by vapor diffusion and that heat transfer takes place by conduction and condensation. The two models are written in dimensionless form, and applied for the same set of standard paper machine data. For basis weights below approximately 0.05 kg d.s./m2 the results are so close that the first, simple model is sufficient. A higher limiting basis weight—approximately 0.16 kg d.s./m2—was previously indicated by comparison of model predictions, assuming the simple model, to extensive sets of machine data from four different paper machines. [Copyright &y& Elsevier]

A mathematical model describing the heat and mass transfer in the dryer section of a paper machine has been applied to the production data from four paper machines. Model predictions for the machine speed are compared to actual machine speeds for a total of 163 data sets. The mathematical model assumes that the temperature and moisture content remain homogeneous in the thickness direction of the sheet. For three paper machines producing paper with basis weights ranging from 0.056 to 0.159 kg d.s./m2 the model predictions are adequate. For the paper machine producing the heaviest grades with basis weights ranging from 0.189 to 0.390 kg d.s./m2 the model predictions are flawed by a systematic error. For low machine velocities/high basis weights the machine velocity is over-predicted and for high machine velocities/low basis weights the machine velocity is under-predicted. This systematic error is caused by the assumption of homogeneous moisture content and temperature within the sheet being severely in error for thick sheets. [Copyright &y& Elsevier]