How to determine the front and back of paper and p

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How to measure the front and back sides of paper and paperboard

paper has two surfaces, one side of paper (copper or polyester) that is pasted to the zero adjustment of the paper machine with respect to various types of experimental machines is the reverse side, and the other direction is the front side. The reverse side is always rougher because of the pattern printed by paper; The reverse side of the paper is loose and the front side is tight. The difference in smoothness between two sides of a paper is generally called the difference between two sides of a paper. It is customary to inspect both positive and negative aspects of physical and optical properties. If only one side is inspected, it must be stated which side is inspected. When using paper, we should consider the problem of the reverse side. If we only print on one side of the paper, we can get the best effect on the front side, which also has 14 years of successful experience in China. All kinds of paper have a certain degree of difference on both sides. The front side of the paper is smoother than the back side, and has a finer organization. The difference between the two sides is due to the actual difference in the fiber structure of the two sides. The front side of the dry paper has a high content of fillers, adhesives, pigments and fine fibers, while the reverse side makes the finishing and reflectance of both sides of the paper different, forming the difference in optical properties of both sides of the paper. Therefore, the quarterly protection of the pressure testing machine is more obvious in terms of thick paper

in general, there are more thick fibers on the back of the paper. The whiteness of the reverse side of white paper is sometimes higher than that of the front side, because a large number of small fibers with low whiteness are excluded from the side on the reverse side of the paper. The sizing degree of paper is often different on both sides, mainly because the amount of rosin on both sides of the paper is different. Generally, the positive sizing test of the paper is effective, because the sizing material is retained more, while the negative sizing test is less effective, because the sizing material is retained less. The paper used on both sides (i.e. front and back) refers to the paper that can be used on both sides at the same time or without obvious characteristics on both sides. Such as writing paper, relief printing paper, typing paper, etc. Copy paper is also double-sided light paper. Because there is no significant difference between the front and back, you can use the front or back, but only one side is used. The paper used on one side means that there is a significant difference in the smoothness of the front and back sides. Such as glossy paper, poster paper, single-sided offset paper, single-sided paint printing paper, etc. These single-sided glossy papers can only be used on the front because of their high smoothness and gloss on the front, and there are significant differences between the front and back

the determination method of the front and back sides of paper and paperboard is briefly described as follows:

1 Fold a test piece by visual method, observe the relative smoothness of one side, and you can often recognize the side from the diamond indentation of papermaking. When taking it, place it horizontally, so that the person's light is at an angle of 45 ° to the paper, and the line of sight is at an angle of 45 ° to the paper, and observe the marks on the paper. You can also observe the paper surface under the microscope to help identify the surface

2. Wetting method water or dilute hydrogen oxidation tensile testing machine Trouser tear method is a kind of test method for the tear resistance of plastic films and thin sheets. Dip the paper surface with sodium solution, drain the excess liquid, place it for a few minutes, and observe both sides. If there is a clear mark, it is the opposite side

3. Tear method hold the test piece with one hand so that the longitudinal direction is parallel to the line of sight and level with the surface of the test piece, and pull the paper upward with the other hand, so as to tear it longitudinally first. Then gradually turn the direction of tearing the paper sideways, tear it to the outside of the paper, and turn over the paper. In this way, on the other side, tear the paper according to the above method, and compare the paper wool on two tear lines. The paper wool on one line is more obvious than that on the other. Especially at the curve where the longitudinal direction turns to the transverse direction, the paper wool is obviously flat. When face up. The burr of paper is even worse

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