The strength of the paper is extremely important for printing and, above all, for further processing. To ensure smooth production, our papers are subjected to different tests to ensure that the paper meets the high requirements placed on it.
Strength is mainly influenced by the type of fibre and the alignment of the fibres in the microstructure of the paper. Chemical pulp naturally has greater strength than mechanical pulp. Depending on how strongly the fibres are aligned, the paper has different strength characteristics in the running direction and crosswise to it.
Tensile strength + tension length
The tensile strength is the maximum tension that a sheet of paper can withstand before breaking. It also indicates factors such as fibre strength, fibre length and fibre bonding. The tensile strength depends on the direction of the fibre and is greater in longitudinal direction than in lateral direction. The tensile strength can be used to determine how resistant paper is to a web break - an important feature of printing paper rolls.
The tear strength of paper is the average force required for a cut in a sheet of paper to propagate, i.e. to continue to tear. The tear strength depends on the direction of the fibre and is greater in lateral direction than in longitudinal direction. Tear strength is an important factor in web offset printing and when producing perforated papers and continuous office papers.
Scott bond strength
The resistance of a paper to the application of force vertically to the surface of the paper (Z direction) is referred to as the Scott bond strength. Scott bond strength is influenced by thickness, filler content and the type of fibre used.
Scott bond strength is an important parameter for heatset and sheet-fed offset printing in particular and for further processing. Insufficient Scott bond strength causes the paper to split along its thickness behind the nip because of adhesion to the surface of the rubber blanket. The use of high tack printing inks increases this phenomenon.
Stiffness describes the properties of paper in the elastic range. It indicates the material's resistance to deformation through external force. Paper has a higher bending stiffness in the direction of the fibre than in lateral direction. To ensure that a book opens correctly, the paper fibres must run parallel to the spine of the book.