Date of Award

6-1961

Degree Name

Bachelor of Science

Department

Pulp and Paper Technology

First Advisor

Dr. Robert A. Diehm

Abstract

Since so many of today's papers are used for applications which require a low hygroexpansivity this property of paper is becoming increasingly important. There are many different types of paper which must be stable against changes in dimensions. Papers used in such diverse applications as recording charts, punch cards, paper recording tapes, and packaging boxes all must be stable against dimensional changes in order to function properly in their usage. In the area of printing papers there is a big demand for dimensionally stable paper. Because offset paper is repeatedly exposed to a wet blanket during the color printing process it must be especially stable. If there is any change in the dimensions of the paper between color applications the whole printing job will be out of register. This is a very large waste and a high added expense. The manufacture of dimensionally stable paper is, therefore, an important concern of a large segment of the paper industry.

For thesis work the author desired to work on a problem which is important to a large portion of the paper industry. The problem of hygroexpansivity met all of the author's requirements for a suitable thesis topic. It is an important problem. It is a problem which has not been solved and over which there is much controversy. It is a problem with which the author was not familiar and therefore would be very educational. Finally, it is a problem with which the author is very interested.

Since the author is interested in developments which can be used directly in production; the areas of pulp freeness and pressure of wet pressing were chosen. Both of these are variables over which the production man has some control. The pressure used on the wet presses on the paper machine can be varied over a definite range without affecting the operation of the machine. The degree of refining and the severity of refining of the stock can be controlled over a wide range. By making adjustments on these two variables, the properties of the finished sheet can be changed considerably. It is the purpose of this investigation to find if there are any methods of pressing and refining which will lead to a more stable sheet of paper.

In order to make an intelligent laboratory investigation of the problem of hygroexpansivity it was necessary to first investigate the work that has been done on the problem by others. Therefore, a survey of the literature was made to find what previous laboratory investigations had been made, and what knowledge in general was known in relation to the problem.

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