Fold resistance is one of the basic mechanical properties of paper and is used to indicate the ability of the paper to resist reciprocating folding. The folding resistance of paper is the number of folds required to measure the tension of a paper after being stretched by a certain force, and then folded back and forth to break it. The number of folds indicates that the unit is double-folded. The degree of folding, according to the lateral cutting test, is the transverse folding resistance. The general head line has a higher degree of folding resistance than that of the transverse direction, which is due to the arrangement of the fibers and the large binding force of the longitudinal fibers.
The degree of folding resistance of the paper depends on the length, strength, flexibility and binding force between the fibers of the paper used for papermaking, and the long, strong and well-integrated fiber paper has a higher degree of folding resistance; When the softwood or pulp slurry is added in the softwood of coniferous wood, the folding endurance is significantly reduced. In addition, the paper's quantification, thickness, tightness, and moisture content have a large impact on the degree of folding. For the same kind of paper made from the same kind of pulp, the addition of mineral filler in the fiber material can increase the tightness, but it will greatly reduce the folding endurance of the paper; when the water content of the paper increases, the folding strength of paper with high strength will increase. However, paper with low strength will decrease.