Spruce Wood Flour for Paper Applications – A Handsheet Study

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Aims: The aim of the study was to investigate if spruce wood flour can be an alternative cellulosic-based wood additive for papermaking.
 Place and Duration of the Study: This study was conducted at the State University of New York, College of Environmental Science and Forestry in Spring 2018.
 Materials and Methods: This study used unbleached wood flour with a particle size distribution between 200 μm to 500 μm and bleached and unbleached wood flour with particle size distribution between 70 μm to 150 μm. Wood flour was added at levels of 2%, 4%, 6%, 8% and 15% based on oven dry fiber content for the first part of the study. For the second part of the study, starch at a level of 0.25%, 0.50%, 0.75%, 1.00%, 1.25%, and 1.50% based on OD fiber content is added to the suspension. The basis weight of the handsheet manufactured was 75 g/m².
 Results: Bulk increased from 2.20 cm³/g to a maximum of 2.80 cm³/g for 15% wood flour addition. Maximum tensile index achieved was 24.75 Nm/g based on a base sheet value of 20.05 Nm/g. Addition of starch has a positive influence on the tensile index, with a maximum value of 41.41 Nm/g at 1% addition. Brightness value of the manufactured handsheets decreased gradually for the unbleached wood flour. Bleached wood flour showed a 1%-point increase above the base sheet brightness of 88.51%. Addition of starch increased the brightness value from 88.51% of the base sheet by up to 4.5%. An opacity increase was achieved for all wood flour additions with the highest opacity value of 95.68% at an addition of 15% wood flour.
 Conclusion: Addition of starch decreases the opacity value of up 1.5% points. Addition of wood flour resulted in a decrease in smoothness by increasing the airflow from the base sheet value of 2564 ml/min by 385 ml/min. at 8% wood flour addition. Adding a line pressure of 1.673 kN/m to simulate calendering resulted in an improved smoothness by reducing the airflow of up to 447 ml/min. Addition of starch showed an overall increase of smoothness by reducing the airflow number by up to 600 ml/min for sheets with and without line pressure.