2.5. Handsheet Formation and Paper Testing

Handsheet formation was used to prepare standard pulp sheets (200 cm²) for physical testing according to T 220 sp-16 [69]. The samples were diluted to 2000 mL (1.2%) with water and disintegrated at 3000 rpm. After that, the stock was diluted to 0.15% with water at a temperature of 22 °C. To make the sheets, the handsheet formation machine was used to turn on water, and the container was filled with water. Then, 500 mL of stock was added to gain the required consistency and rapidly allow water to move down the cylinder (in 3 ± 1 s) using rotary oscillation for stirring. Immediately after the water had drained from the handsheet, the container was opened, and the sheet was picked with blotting paper, before being dried and weighed to calculate the stock concentration.

After constructing a standard sheet for physical testing (1.22 g), the wet test sheet was placed on a clean mirror-polished plate and covered with another dried blotter ready to receive the next couch blotter and sheet. After that, the sheets were placed in the press template to conduct the first round of pressing at 50 psi for 5 min. Then, the polished plates were removed after first pressing them and placing them on another side, and 50 psi was applied for 2.5 min. Subsequently, the sheets attached to the plate were removed from the press template and placed in drying rings. The sheets were dried according to the standard conditions specified in T 402 sp-08 [70] (23 ± 1 °C and 50 ± 2% RH humidity) until equilibrium moisture was achieved, allowing the sheets to become fully dried in the ring before removing them from the plates. Pulp from standard paper sheet samples (200 cm²) and a grammage of about 60 g/m² was prepared for the determination of dry strength properties according to T 205 sp-02 [71].

The samples were conditioned at 50 ± 2% RH and 23 ± 1 °C according to T 402 sp-08 [70] for at least 4 h. Handsheets were made and their strength properties were tested according to T 220 sp-16 [69]. For the handsheets, the properties tested were the tensile index (T 494 OM-13) [72], tear index (T414 om-12) [73], burst index (T 403 OM-15) [74], and double fold number (T 511 OM-13) [75]. Analysis of the physical strength of pulp was performed according to TAPPI standard methods with standard 60 g/m² sheets.