Date of Award
Bachelor of Science
Pulp and Paper Technology
Dr. David Peterson
The objective of this study is to compare two different pulps, a softwood kraft pulp with a groundwood pulp, to see if there is any difference in the behavior of their sheet properties as they are recycled. Neither pulp was dried before the experiment began. The pulps were each refined to three different freeness levels to determine the effect of initial freeness on recycled sheet properties. Tests for tear, tensile, zero-span tensile, opacity, brightness, scattering coefficient, absorption coefficient, and porosity were performed on the sheets in order to determine the effects of recycling on those sheet properties. A Kajaani fiber length analysis was performed after each run to determine if the fibers were being cut during recycling.
For the chemical pulp, the tensile strength was found to decrease with recycling. Tear increased and then fell as it was increased. Brightness, opacity, scattering coefficient, absorption coefficient, were relatively unaffected by recycling. The porosity increased as recycling increased.
The mechanical pulp behaved the same as the chemical pulp for tensile strength and porosity. The tear strength was unaffected by recycling, but the data for the tear strength may have been bad. The opacity and brightness fell with recycling. The scattering coefficient and absorption coefficient were unaffected by recycling.
Different pulping methods yield pulps that behave slightly different when they are recycled. It may be expedient to compare other pulping methods with the ones in this report following the same experimental design.
Smith, Heath A., "The Effects of Recycling on a Never-dried Softwood Kraft Pulp Beaten to Different Initial Freeness Levels" (1996). Paper Engineering Senior Theses. 509.