Date of Award

12-1978

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

The purpose of this study was to determine the effects of certain drying variables on some physical strength properties when these variables were controlled to bring about overdrying conditions. The variables under study were contact time on the dryer can (% moisture) and different percentage hardwood-softwood compositions. From the study it was discovered that overdrying actually increases tensile values but mullen and tear values did indeed decrease.

The object of the following report was to see if there was a decrease, if any, in certain physical properties and to what degree. If overdrying a sheet actually decreases the physical properties by a very small amount the following is proposed. If one can add an extra wet press roll on the same could be obtained when entering the first dryer section. With a higher consistency going into the first dryer section (of approximately 5-10%), the amount of water to be removed would be substantially decreased. With this increase in consistency the sheet could be subjected to overdried conditions. With the sheet in an overdried state (depending of course on customer order). The initial cost of the extra wet press roll could be paid for with the energy savings obtained by running the two dryer cans steamless. Therefore, if a sheet could be overdried (without sacrificing production) and then rewetted with minimal fluctuations in physical properties an economical benefit would result.

The following is a study to see if indeed this idea could be put into practice. The results were then related to tensile, tear and mullen in an attempt to establish a relationship of overdrying to these physical characteristics. The tensile, tear and mullen were all run according to respective Tappi Standards.

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