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2.1.1. Water Content of Pulp
Because as-received pulp contains some water, water content had to be fi rst determined so that the weight of fi bers (dry weight) could be known. This was done by drying the pulp at 120 °C overnight in an oven. Five samples of about 5 g each were used to determine the average moisture content for each type of pulp used.
2.1.2. Disintegration
As-received pulp needs to be disintegrated in order to separate the fi bers from one another. This was done in a British Standard Disintegrator by mixing 30 g of dry fi bers in about 2 L of water and then operating the Disintegrator at a speed of 3000 RPM for 10 min.
2.1.3. Re fi ning
Two-thirds of the handsheets (both softwood and hardwood) were prepared from re fi ned fi bers. Re fi ning was performed after disin- tegration using a PFI mill in accordance with TAPPI ’ s test method T-248. [39] The PFI mill required 30 g dry fi bers at a consistency of 10% (total mass of fi bers þ water = 300 g). Because the suspen- sion obtained after disintegration was too dilute for this purpose, excess water was removed using vacuum fi ltration, and the fi ltered pulp was diluted with water to make a total of 300 g. The mixture was then evenly distributed along the walls of the PFI mill ’ s bowl. The mill was operated for a total of either 1000 or 2000 revolutions to obtain two different levels of re fi ning, indicated by “ R ” (re fi ned) and “ R þ ” (heavily re fi ned), respectively. 2.1.4. Stock Suspension After disintegration, and optional re fi ning, water was added to the pulp (containing 30 g of original dry fi bers) to make a 10 kg suspension (consistency = wt%of fi bers = 0.3%) of fi bers in water.
2.1.5. Freeness Measurement
Freeness is a measure of how quickly water drains from a dilute suspension of pulp, and is affected by surface and swelling char- acteristics of fi bers. [42] Freeness was measured using a Canadian Standard Freeness (CSF) instrument in accordance with the TAPPI test method T-227. [42] One liter of the 0.3% consistency stock suspension prepared above was drained through the instru- ment ’ s screen and the volume of the fi ltered water was noted. This volume, after correction using a supplied temperature- volume chart, was noted as the CSF of the pulp.
2.1.6. Making Handsheets
Figure 1. Procedure for making handsheets in lab, closely following TAPPI ’ s test methods.
As expected, 1 L of stock produces a handsheet that ultimately weighs 3 g after water is drained and the fi ber web is dried. The amount of stock suspension used was adjusted to produce a handsheet weighing either 1, 3, or 5 g. A standard papermaking apparatus consists of a tank fi tted with a metal screen at the
Paper. TAPPI ’ s test method T-205 was followed for the produc- tion of handsheets. [36] A procedural schematic is shown in Figure 1 with the process parameters shown.
2400589 (3 of 10)
Phys. Status Solidi B 2025 , 2400589
© 2025 The Author(s). physica status solidi (b) basic solid state physics published by Wiley-VCH GmbH
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