Investigation of the CMP Pulp Yield Variations on Its Strength and Optical Properties

In this research, the chemimechanical pulps (CMP) with different yields were prepared by using the mixtures of constant raw materials comprising Iranian hardwood species such as hornbeam (44%), poplar (31%), maple (15%) and salix (10%). This research was aiming to study CMP pulp properties variations in yields lower than standard limit (85%). Four different yields (84, 80, 73 and 67%) were achieved by changing the cooking parameters including temperature, time and cooking liquor consumption ratio,. Freeness of the pulp, strength and optical properties of the 60 g/m2 handsheets were measured. . The results showed that the initial freeness was reduced with 17 unit reduction in CMP pulp yield, while all strength properties including tear, burst and tensile indices were increased to 42, 100 and 29 percent, respectively. The Brightness and opacity of the obtained pulp was reduced with reduction of yields and with 17 unit reduction in CMP pulp yield (from 84 to 67 percent), the brightness about nine percent and the opacity less than one percent were decreased.