CD-Laboratory for Surface Chemical and Physical Fundamentals of Paper Strength
The CD-Laboratory for surface chemical and physical fundamentals of paper strength was established in March 2007. The core area of this CD-Lab is the analysis of physicochemical properties of individual fiber - fiber bonds. Different aspects affecting the magnitude of inter fiber bond strength are investigated in a cooperative approach involving 3 university institutes, using a range of different methods. A comprehensive picture of fiber-fiber bonds ermerge from this and enhances the understanding of strength development in paper.
The results of fundamental research are directly applied by the industrial partners.
Working groups of the CD-Laboratory
Institute of Solid State Physics (TU Graz)
Institute of Physics (MU Leoben)
Institute of Paper, Pulp and Fiber Technology (TU Graz)
At the Institute of Solid State Physics the surface and the bulk chemistry of the fibers is analyzed using Attenuated Total Reflection Fourier Transform Infra Red Spectroscopy (ATR - FTIR).
In Leoben the morphology of the fiber surfce and the bond strength is examined using Atomic Force Microscopy (AFM) methods.
Institute of Paper, Pulp and Fiber Technology:
The research work of the Institute for Paper, Pulp and Fiber Technology within the CD-Lab can be devided into two parts. The first part was concerned with the development of a non-destructive method for measuring the bonded area of single fiber-to-fiber bonds. This method is based on polarized light microscopy and has been introduced by D.H. Page. The difference compared to the method of Page is that the lower fiber is dyed.
The results of investigations, using the polarized light microscopy, are compared with those of a 3-dimensional microtome serial sectioning technique (microtomy). Furthermore, the morphology of fibers and fiber-fiber crossings is examined with the help of the microtome method.
The comparision between the two different methods showed that the polarized light microscopy is asuitable tool for measuring the bonded area of single fiber-to-fiber bonds. There a two advantages using this method:
basis for specific bonding strength measurements
The second part is concerned with the development and construction of a micro bond tester.
This device enables the determination of the
single fiber tensile strength
breaking load and bonding energy of indivdual fiber-fiber crossings
bending stiffness of single fibers
These tests provide knowledge regarding fiber and bond parameters (modulus of elasticity E, breaking load F, stresses σ, etc.) which can be used as basis for network modeling. The models in turn will contribute to a better understanding of paper fracture mechanics.
Since the end of 2010 a new Module within the CD-Laboratory was launched having two objects, to get a better understanding of the bonding mechanism of viscose fibres and wood pulp fibres, and to investigate the effects of viscose fibres in paper products. Viscose fibres are synthetic fibres made from natural polymere, so one can make them with defined dimensions and cross section areas. For example, there are round fibres, flat fibres, hollow fibres and so on.
It is also feasible to add additives and therefore induce surface charges to the fibres. For this reason these fibres gives the opportunity to change specific properties of paper such as water retention value, tear resistance and breaking length.
The Lenzing module was launched to investigate the interaction between hemicelluloses (xylan) and cellulose. The analytical methods, developed within the CD-Laboratory are used to describe these interactions in more detail. Moreover, the influence of xylan on mechanical properties of the produced papers (e.g. tensile stiffness) is determined, according to the amount and quality of the added xylan samples.
The effect of six varibales (e.g. temperature and pH) is alanyzed regarding the amount of deposited xylan on the fibers. Moreover, physical properties of the xylan modified fibers are determined.
Further, the investigation of the surface texture of the fibers, before and after adsorption, is of interest to describe the mechanisms during precipitation of xylan and the distribution on the fiber surface. Therefore, a co-operation with the Montanuniversität Leoben (Institute of Physics) was launched to analyze the surface hardness by atomic force microscopy.
In addition, single fiber-fiber joints of fibers and xylan modified fibers are made to determine the bonding energy, bonding strength and bending stiffness of these joints. Thereby, the influence of xylan on the bonding mechanisms and strength properties of single fiber-fiber joints are investigated and contributes to the general acceptance of the bonding mechanisms between fibers in the paper network.
Dipl.-Ing. Dr.techn. Wolfgang Johann Fischer (Mondi Module)
Dipl.-Ing. Frederik Weber (Kelheim Module)
Dipl.-Ing. Albrecht Miletzky (Lenzing Module)
All publications can be found here.
Mondi Frantschach GmbH, Lenzing AG, Kelheim Fibres GmbH
March 2007 - February 2014