Date of Award

4-1996

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Dr. Raja Aravamuthan

Abstract

Through the application of enzymes, the freeness of recycled pulps can be improved; however, with the improvements in freeness, there may also be a loss of strength. As enzyme effectiveness depends on the fiber degradation and fines content of the pulp, it also. depends on the amount of recycling that the pulp has undergone.

To evaluate the relationships that exist between enzyme treatments and the number of recycles the fiber has undergone, a virgin CTMP was recycled three times. At each recycle enzymes were applied to the pulp. One leg of the experiment involved a repetitive enzyme treatment of the pulp, before each recycle.

Freeness improvements were achieved at all levels of recycling. The single enzyme treatments were the most effective at improving freeness. The biggest improvement (16.4%) was achieved with a single enzyme treatment after two recycles.

Significant losses in sheet strength were observed. Strength losses were more severe in the repeatedly enzyme treated pulps. The repeated enzyme treatment of pulp accelerates the degradation of fibers. The reduction of surface area in the fines fraction as a result of enzyme action can be attributed, in part, to the strength losses of the pulp.

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