Abstract
Among bio-based reinforcement additives for paper existing on the market, microfibrillated cellulose (MFC) turned out to be a promising material, showing outstanding potential in composites science. Its relevance in papermaking as a new family of paper components was suggested more recently. There remains a number of constraints limiting the promotion of their use in papermaking, mostly related to their high cost and effect on dewatering resistance. Also, contrasting results reported in the literature suggest that the effect of fibrillation rate and quantity of such cellulosic additives in a furnish on the technological paper properties needs further research. The purpose of this study is to produce and characterize different MFC-like fine fibrous materials of varying particle size and degree of fibrillation from the same batch of pulp through mechanical treatment or fractionation. The effect of the thus obtained fine fibrous materials on paper properties is evaluated with respect to their concentration within a fiber furnish. We compared: (i) a mixture of primary and secondary fines isolated from the pulp by means of a purpose-built laboratory pressure screen; (ii) MFC-like fine fibrous materials of increasingly fibrillar character obtained by refining and subsequent steps of high-pressure homogenization. The morphology of the different materials was first characterized using flow cell based and microscopic techniques. The thus obtained materials were then applied in handsheet forming in blends of different proportions to evaluate their influence on paper properties. The results of these experiments indicate that all these products lead to a substantial decrease in air permeability and to improved mechanical properties already at low concentration, independent of the type and morphological character of the added fine cellulosic material. At higher addition rates, only highly fibrillated materials allowed a further considerable increase in tensile and z-strength. These observations should help to allow a more targeted application of this new generation of materials in papermaking, depending on the desired application.
Highlights
In a competitive environment resulting from globalization and various other economic factors, balancing sustainability and profitability is a challenge and a huge opportunity for the paper industry
We compared: (i) a mixture of primary and secondary fines isolated from the pulp by means of a purpose-built laboratory pressure screen; (ii) microfibrillated cellulose (MFC)-like fine fibrous materials of increasingly fibrillar character obtained by refining and subsequent steps of high-pressure homogenization
A sample of this pulp was refined in an industrial double-disc refiner to 38SR and fractionated using a lab-scale pressure screen equipped with a perforated plate to separate the primary fines already contained in the unrefined pulp and the secondary fines produced during refining from the fibers [20]
Summary
In a competitive environment resulting from globalization and various other economic factors, balancing sustainability and profitability is a challenge and a huge opportunity for the paper industry. A possible way to produce new competitive products is to develop efficient strengthening additives to meet the requested mechanical properties of the final product at a reduced raw material input In this context, cellulosic nanomaterials, such as cellulose nanofibers and nanocrystals, as well as the coarser microfibrillated celluloses (MFC) have emerged over the last twenty years as promising and sustainable reinforcement materials, showing outstanding potential in material sciences. It is has been reported that pulp origin and treatment, as well as both type and amount of added MFC, affect the final paper overall properties, leading to sometimes contrasting results [5,6,7] This wide range of variability represents a good opportunity to tailor the performances of paper if the effects of MFC additives become better understood
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