Abstract
To design new and optimize existing paper and board material an understanding of how the paper making process affects the final paper properties and how we can control them is neccesary. There is a link missing between pulp properties and machine made paper properties. The aim with this work is to close this gap by proposing an engineering model which, based on furnish properties, makes it possible to predict tensile property profiles in MD and CD.
Two series of hand sheet trials were made to validate and formulate the model. The purpose with the first trial was to validate that the geometric mean of the studied properties in MD and CD is constant and equal to the isotropic value. The second trial was made to find relations between anisotropies of the studied properties and the fibre anisotropy.
The model was applied on a press draw trial made on a production machine. The strain and tensile property profiles were measured and predicted based on laboratory measurements on the furnish. The predictive capability of the model was regarded as fairly good, especially since the general behaviour of the paper properties was correctly captured. The deviation of predictions compared to measurements were around 10% or less for most of the evaluated positions and properties, except for MD tensile energy absorption index that was poorly predicted.
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