# Properties of Grey Board Paper

- May 03, 2018-

1. Quantitative

It refers to the weight of the unit area of paper, expressed in g/m2, which is the weight of one square meter format paper. The level of paper quantification determines the physical properties of the paper, such as tensile strength, tear strength, tightness, stiffness, and thickness. Therefore, according to the characteristics of the equipment, arranging the prints corresponding to their performance to be produced in order to reduce the consumption, improve the product quality and the efficiency of the equipment.

2. Thickness

It is the thickness of the paper, the unit of measurement is usually expressed in mm. Thickness is closely related to the quantitative and tightness. In general, the thickness of the paper is large and its quantification is correspondingly high, but the relationship between the two is not absolute. Some papers are thin, but their quantification is equal to or greater than that of thicker ones. This shows that the degree of tightness of the fibrous structure of the paper determines the basis weight and thickness of the paper. From the point of view of the use effect, it is very important that the paper thickness is uniform. Otherwise, it will affect the auto-feed, sizing, etc.

3. Tightness

It refers to the weight per cubic centimeter of paper, using g/cm3. The tightness of the paper is calculated from the formula and thickness according to the formula: D=G/d*1000, where: G represents the paper's ration; g is paper thickness of.

Tightness is a measure of the degree of structural compactness of the paper. If the degree of tightness is too large, the paper will be easily brittle, and the opacity and water absorption will be significantly reduced, making it difficult to dry.

It is also easy to calculate the board thickness based on the above formula. Its formula is: d = G/D.

Example: Find the thickness of 500g/m2 double grey cardboard (its tightness taboo 0.625g/cm3, which is also our common indicator). 500g/m2÷0.625g/cm3=0.0008m=0.8mm

The unit conversion of m2 and cm3 mentioned in the previous step should be remembered, otherwise it is easy to produce misunderstandings. The method is: cm3/m2=(1*0.000001)m, converted into mm is our actual thickness.

4. Stiffness

It is the performance of the paper that resists the collapse of another object, and it is also the rough appearance of paper fibrous tissue.

5. Smoothness

It refers to the degree of surface roughness of the paper, expressed in seconds and measurable. The detection principle is: the time it takes for a certain solvent's air to pass through the gap between the glass plate surface and the sample surface under a certain degree of vacuum and pressure. The smoother the paper surface, the slower the speed at which the air passes, and vice versa, the faster the air passes through.

6. Flexibility

It refers to the dimensional variation that occurs when the paper absorbs moisture or water is lost. The softer the fibrous structure of the paper, the lower the tightness, the higher the paper's stretch rate; conversely, the lower the stretch rate.

7. Water content

Water content in cardboard. Generally speaking, it is standard. Double gray board moisture content of 8-12%.

8. Vertical and horizontal

It refers to the direction in which the paper fibers are arranged. During the papermaking process, the direction of fiber running in the direction of the paper machine is the longitudinal direction of the paper. It can be identified from the sharp corners of the web marks. Vertical to the vertical direction is the horizontal direction. The vertical paper grain has small deformation value, and the horizontal paper pattern has a large amount of stretching and deformation.

9. Air permeability

In general, the thinner the paper and the lower the tightness, the greater the air permeability. The unit of air permeability is ml/mim (ml/min) or s/100 ml (second/100 ml), which means the amount of air that passes through the paper in one minute or the time required to permeate 100 ml of air.

10. Positive and negative sides

At the time of papermaking, the pulp was attached to the stencil to determine the dehydration by filtration. In this way, if one side of the net is lost due to fine fibers and fillers with water, net marks are left and the paper surface is thicker. On the other hand, there are no nets that are fine. Smooth, so that the paper forms a positive and negative surface difference, although the production has been dried, calendered, there are still differences on the positive and negative.