Fibres and bonding Bonding between cellulosic fibres (i.e. inter-fibre bonding) and its relationship to the mechanical and optical properties of paper was studied intensively in the 1950s and 1960s. Many results published in those years still have great value. Extensive literature reviews are available that provide more detailed information than what we can give here.1,2,3
Internal stresses in paper sheet Deformations in the internal structure of fibres and bonds explain qualitatively the changes caused by drying in the microscopic and macroscopic properties of paper. Such deformations are seldom directly observable. Therefore, concepts such as internal stresses, dried-in stresses, or dried-in strains often find use in explaining the effects of drying
Mechanical properties of dry fibres The mechanical properties of single dry fibres have also been the subject of considerable study, despite the tedious measurements involved. As an example, Figure 1 illustrates the wide distribution of tensile strength values. The high variability arises from the biological raw material and from the nonuniformity of pulping processes. In
Mechanical properties of wet fibres The properties of wet fibres significantly affect the structure of the fibre network and the bonding potential of fibres, whereas the properties of dry fibres contribute, together with bonding, to the strength of the dry fibre network. The network structure of paper depends on the dimensions and conformability of wet
The effects of pulping on fibres In addition to the type of raw material, pulping, bleaching and beating have crucial effects on the pulp properties. Two basic classes are chemical pulp and mechanical pulp, as illustrated in Figure 1. In making chemical pulp, wood is disintegrated chemically into fibres by cooking wood chips into kraft
Raw material effects on fibres Paper usually consists of wood fibres, though non-wood fibres can be important locally. In specialty papers, non-wood fibres have global use. Fibre properties vary considerably with the wood species (Figure 1) and growth site and with the pulping and papermaking treatments that the fibres undergo. Because of the stochastic nature
Fibres and bonds The properties of paper are determined by the properties of the various particles that it consists of and by the conditions during papermaking. Fibres, pulp fines and fillers are the most typical particles used in papermaking. Web forming conditions affect the orientation of fibres, and web dewatering conditions affect the z-directional distribution
Effect of binder latex on printability of paper and board Printing is usually the final application of graphical papers before they are delivered to the ultimate consumer. The demands of the printer determine what paper quality is all about. Different printing techniques require different quality parameters. In the following, offset printing — divided into heat set
Impact of latex on the paper coating process and paper quality Influence of latex on the coating colour In the preparation of coating colours latex gets into contact with other dispersed systems (mainly pigment slurries) and dissolved materials (e.g. carboxy methyl cellulose (CMC), starch, synthetic thickeners, dispersants). Although rheology additives play the main role in
Properties of styrene-acrylic and styrene butadiene-latexes The glass transition temperature (Tg) of styrene-acrylic and styrene butadiene copolymers can be varied within a wide range by changing the ratio of hard monomer (styrene) and soft monomer (butadiene respectively n-butylacrylate). Papers for rotogravure printing require a very flexible coating layer, which can easily adapt to the surface
