An Enzymatic Fiber Modification Method for Enhancing Tissue Properties

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Title: An Enzymatic Fiber Modification Method for Enhancing Tissue Properties
Author: Wallace, Jeff Thomas
Advisors: Dr. Joel J. Pawlak, Committee Chair
Dr. John A. Heitmann, Committee Member
Dr. Dimitris S. Argyropoulos, Committee Member
Abstract: Retail consumers of tissue products desire the highest softness at the lowest cost. The softness of a product can be broken down into two components, the bulk (i.e. structural) softness and the surface softness. Traditionally papermakers have used a variety of tools, such as refining, beating, chemical addition, etc., to enhance the softness of paper. The use of enzymatic treatment to enhance the softness of paper is less common, but offers a unique way to modify the chemical composition and ultra-structure of the papermaking fibers. Procter and Gamble has developed a patented process for enzymatically modifying and degrading cellulose fibers to produce softer tissue grade paper. The principle of this technology is that by selectively degrading a cellulose fiber, the bulk softness of the resulting fiber structure can be increased. The main goal of my research was to investigate the fundamental interactions of enzymes with cellulosic substrates in order to better understand the commercialized fiber modification process and the potential for new properties and products this technology offers. A duplication of the Procter and Gamble patented technology was carried out in the research labs using different enzyme concentrations and incubation times. From these duplication experiments, it was found that the patent claims could be reproduced in our laboratories. Furthermore, the enzyme dosage and incubation time could be optimized. An investigation into localized fiber degradation produced by the enzymatic treatment of the fibers was carried out. This investigation was broken into three parts and the first part was to characterize enzyme absorption on softwood fibers by investigating the isolation of enzyme activity to fiber defect (notch/kink) areas using microscopic and image analysis techniques. The results along with the patent duplication experiments relates back to how enzymes affect the fibers to create weaker and more compressible fibers as shown by the microscopic and the zero-span tensile strength results. The results proved that notch/dislocation areas of the fiber are more accessible areas for enzymes and degrade. The results also showed that as incubation time increased, the fibers began to break up and fragment at dislocation areas for enzyme concentrations of 0.5% and higher. The second part of the localized fiber modification study was to study enzyme attachment to softwood fibers. This was tested functionally by attempting to first absorb the enzymes onto fibers and then incubate the fibers with untreated fibers. The sheet properties of jointly incubated fibers and separately incubated fibers were compared. The results indicated that enzymes absorb and desorb from the fiber, reattaching and redistributing to other fibers. The third part of this investigation was to study the effect of enzyme treatment on wet fiber flexibility for refined softwood fibers. The effect on wet fiber flexibility relates back to how enzymes affect the compressibility, bending stiffness and modulus of the sheet as a whole, which is important for improving bulk softness. From the results, it can be concluded that enzymatic degradation affects fiber flexibility as a function of incubation time up to 4.5 hours at 0.5% enzyme concentration. Beyond this time flexibility begins to decrease due to fiber length reduction. Also, two other studies are included in the appendices sections of this thesis (Appendices F & G). The first report is a softwood fiber defects quantification and assessment study. This study attempted to create a method to quantify different types of defects (kinks, dislocations, curls, etc.). The second report is a study on pre-enzyme treatment of fibers to introduce fiber defects with Hobart kneading. It was found that Hobart kneading does not create new defects, but does enhance existing defects and also introduces curl and kink into the fiber.
Date: 2006-05-03
Degree: MS
Discipline: Wood and Paper Science

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