Blending of different pulps prior to Low consistency (LC) refining is common operation in paper making. LC refining is a process used to modify the morphology of the fibres in order to increase tensile strength of paper. The aim of this dissertation is to understand the difference in mechanism between separate and co-refined pulp fibre mixtures and to achieve a scaling law to understand tensile increase. This work was conducted in three separate studies using vastly different refining

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... , namely compression refining, PFI and pilot scale disk refiner. We examined the tensile strength, T response of mixture of softwood (NBSK) and hardwood (eucalyptus) to various energy, E and intensity, I of treatments. We advanced for the first time a scaling law of the form TL/k=f(E,I) which collapsed all data for the different suspension and argued its utility through consolidation theory. Here k is the permeability of the suspension and L is the fibre length. Hence, we achieve similarity between all treatments. We also note a curious result that ordering of the refining treatment affects the tensile strength increase. We demonstrate that a large tensile strength is gained if the pulp suspensions are mixed first, and then refined, as opposed to refined then mixed. Further work is required to understand this effect.