The local distribution of fillers in the z-direction of paper (PDF)

Inhaltsangabe:Introduction:
It is important to determine the distribution fillers in thickness direction of paper. However, the techniques that are available are limited in precision and accuracy. This thesis describes a new method for the determination of fillers in the z-direction of paper. The method is based on a splitting technique that offers a good reproducibility and provides good layer uniformity. The new method is used to estimate the effects of different factors of influences affecting the fillers distribution.
During sheet forming a large amount of water is removed. This dewatering process creates an irregular distribution of fillers across the thickness of the paper. Therefore, the description of the distribution of fillers in the thickness direction is critical to optimize paper properties. The techniques currently available for this kind of characterization have limitations in terms of repeatability, resolution or precision. Another limitation to currently available techniques is the lack of a good sampling area. Considering the large effect of fillers on many paper properties, the ability to measure and thus control the filler distribution in the z-direction helps to control sheet structure, reduce two-sidedness and improve paper properties such as internal bond. Inhaltsverzeichnis:Table of Contents:
Acknowledgements2
Abstract3
Index of contents4
1.Introduction6
1.1Paper structure7
1.1.1Three dimensional network8
1.1.2Formation11
1.2Fillers12
1.2.1Effects of filler loading on the properties of paper12
1.2.2The main fillers:14
1.3Retention and dewatering16
1.3.1First-pass retention and true retention17
1.3.2Agglomeration and flocculation20
1.3.3Retention fundamentals:23
1.3.4Filler distribution24
1.4Measuring filler content and distribution25
2.Materials and methods28
2.1.1Measuring filler distribution28
2.1.2The procedure of splitting33
2.1.3Acquisition of the images35
3.Results and Discussion37
3.1Settings of the scanner38
3.2Different backgrounds40
3.3Repeatability of the method42
3.4Influence of the position of filler addition43
3.5SC Paper with 42,8 % GCC53
3.6TMP - Paper 20% GCC57
3.7Fine paper with 20 % and 30 % of GCC63
3.8Different positions of adding GCC73
4.Summary83
5.Sources84
6.List of Figures86 Textprobe:Text Sample:
Chapter 1.3.4, Filler distribution:
The distribution of filler material in the paper depends on the forming process. Fillers can be entrapped mechanically into the web, [...]