Date of Award

4-1978

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

Previous laboratory investigations of the effects of paper machine draw tension on paper properties have been qualitative in nature. It is the object of this study to deal with quantitative values in examining the wet press area of the paper machine. Typically, by increasing draw tension machine direction tensile is improved, while elongation and cross direction tensile degrade. The establishment of known responses in paper properties to exact units in web tension would allow a control system to operate this draw area at optimum conditions. A cantilever beam force transducer was used to directly measure web tension at specific draw location in the press section.

Two fiber furnishes were used to study the effect of fiber length and fibrilar area with sheet directionality. The higher the percentage of softwood in the furnish, the more internal bonding could be oriented. The final paper properties as the draw tension between the couch and first press were inconclusive. Further studies may help substantiate the phenomenon of improved cross direction tensile and elongation. Machine direction tensile was the most improve in the draw between the first and second press at the center of the draw tension range. A water balance around the wet press together with porosity and Canadian standard freeness tests would aid in understanding the process of directionality. The water and fibril movement with respect to each other, determines the bonding site location, within the web. Straining the web after hydrogen bonding has occurred, rapidly orients the bonds, relative to a similar draw tension while bonding is occurring. The critical tension is rapidly met after which degradation of strength is extreme.

Stabilization of the tension measuring device as recommended would provide exact figures of draw tension. The simplified web marking device would provide an easy means of measuring web elongation. Substantial gains are possible in tensile and elongation properties, justifying further study in this subject.

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