Dilek YAYLALI, Canan URAZ, Esat GÜMÜŞKAYA
Table 1. Kraft pulping conditions Cooking parameters
Unit
Value
Temperature
°C
170
Pressure
bar
10 80 90
Time required to reach max temp.
min min min
Pulping time
Total pulping time
170
Na 2 S
% %
5
NaOH
15.5
Liquor/raw material
5/1
The digested materials were washed with hot water to remove the dissolved substances and black liquor. After the removal of residual chemicals, the uncooked bundles of fibre were separated from the pulp and disintegrated using a lab-type disintegrator on a lab-type screen with a 0.15 mm slot width. The sieved parts were dried to a dry matter percentage of 20 – 25%, mixed, and then placed in polyethylene bags. The bag vent was left open for 24 h to achieve moisture equilibrium. The moisture content was determined using the TAPPI T 210 standard [TAPPI T 210:2003]. The dewatered pulp was stored in a refrigerator for further studies. The pulp yield for each batch was determined using the oven-dry weight of the hemp bast fibres that were initially charged into the digester. The pulp yields were calculated using the following equation [Ruraltech 2020]: ܻ݈݅݁݀ ൌ ௪ భ ௪ మ ݔ ͳͲͲ (1) where w 1 is the oven-dry weight of the hemp bast fibre pulp and w 2 is the oven- -dry weight of the hemp bast fibres initially loaded into the digester. Beating The strength of a handsheet significantly depends on the strength and bonding capacity of the fibres. The cooked hemp bast fibres were beaten using a Hollander beater (L&W, model type: 3-1) for fibrillation. A suspension of tap water and cooked hemp bast fibre (pulp) with a consistency of 1.76% was prepared and used as the stock suspension for the blending studies. The prepared slurry was disintegrated in the raceway of the beater for 30 min before the beating motion was initiated by decreasing the distance between the beater wheel and plate. The beating degree of the pulp was determined using the Schopper Riegler-type beating degree tester (L&W, model: 2-4) and the TAPPI T 227 standard [TAPPI T 227:1999]. The beating degree was calculated as follows: ሺιሻ ൌ ሺଵି ௪௧ሻ ଵ , (2)
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