ABSTRACT
Section III is authored by Dr. Makio Hasuike, Hiroshima Research and Development Center, Mitsubishi Heavy Industries Ltd., Hiroshima, Japan.
IV. Dimensional Characterization of Fibers 950 A. Fiber Length 951 B. Fiber Curl and Kink 969
V. Other Dimensional Parameters Used to Characterize Fiber Raw Materials and Fiber Networks 975
VI. Dimensional Characterization of Shives, Slivers, and Fines 994 A. Shives and Slivers 994 B. Fines 995
References 1002
I. INTRODUCTION
A quantitative knowledge of the geometric structure of paper and board is funda mental to the understanding of why these materials possess the properties they exhibit and how those properties are changed when the structure changes. In this chapter, some of the methods used to determine several important structural para meters are described and the principles behind these testing methods are discussed. The internal structural parameters that are the most important depend on whether one considers a relatively dense, highly bonded material such as linerboard or a low density material such as tissue, whether one is primarily interested in mechanical or other physical properties, and, within either of these last two categories, what type of physical (e.g., opacity or absorbency) or mechanical (e.g., elastic properties or prop erties at failure) characteristics are of particular interest. Perkins [152,153] identified the network parameters that are considered in theories relating to mechanical prop erties as follows:
1. Fiber length (including length/width and length/thickness ratios) and its distribution
2. Fiber curliness and kink 3. Fiber segment length (distance between bond centroids along a fiber) 4. Fiber cross-sectional shape (includes area, width, wall thickness, degree
of collapse, aspect ratio); characteristics of the distribution of these quantities
5. Mechanical properties of fibers 6. Size and mechanical nature of the fiber-fiber bond area 7. Percentage of the fiber surface bonded to other fibers (relative bonded area) 8. Fiber orientation distribution 9. Sheet density and uniformity; distribution of mass
10. Sheet shrinkage strains
For testing related to other (physical or mechanical) properties, one may need information regarding some or all of the above parameters plus additional informa tion on other properties such as
11. Basic weight (grammage) 12. Moisture content 13. Apparent fiber density
14. Proportions of cell wall layers (compound middle lamella, SI, S2, S3) 15. Filament winding angles (microfibril angles) 16. Conformation of molecular components 17. Surface charges 18. Internal surface volume (including pore size distribution) 19. Electrical conductivity and dielectric constant 20. Acoustical conductivity 21. Indices of refraction
The above list, by no means complete, includes many items that are considered in detail in other chapters. In this chapter we concentrate on methods for ascertaining some important parameters related to internal structural geometry. Special attention will be given to item 8, fiber orientation distribution, because the amount of pre viously published information available in the paper testing literature is quite limited despite the importance of this parameter.
