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This laboratory handsheet and Fourdrinier pilot paper machine study examine the suitability of willow as a commercial hardwood pulp replacement including utilizing recycled pulp for paper production. The hand sheet study contains 16 different and the pilot paper machine study eight different furnish mixtures. For both studies, the base sheet consists of a 40% softwood and 60% hardwood commercial pulp mixture, followed by replacing the hardwood with bleached willow Kraft pulp. Deinked pulp, as recycled fibres, at 5% increments up to 100% for the handsheet study and at 10%, 20%, 30%, 50%, 70% and 90% for the pilot paper machine study is added to the base pulp mixture. Both the handsheet and the FPPM study revealed that willow Kraft pulp can replace commercial hardwood pulp fibres. Basis weight, calliper and stiffness as related properties showed comparable results for the handsheet study. Willow Kraft fibres tend to be bulkier and denser than the used hardwood fibres.
Tensile and tear index show comparable properties for the handsheet and pilot paper machine study, except for the 50%, 70% and 90% DIP containing paper sheets.
Porosity values for the hansheet study showed lower results than the base sheet, whereas the FPPM study showed higher results except for the 70% and 90% DIP containing handsheet. Comparable results are shown for opacity. Brightness levels were significantly lower due to the lower brightness of the manufactured willow Kraft and deinked pulp fibre furnish.
Despite the opportunity of replacing commercial hardwood with willow, more research needed to optimize willow into pulp fibres and preparation of the fibres for papermaking.