Ply adheasive strength refers to the degree of adhesion between corrugated paper sheets. Common corrugated cardboard has three layers of cardboard and five layers of cardboard. The three-layer paperboard is formed by bonding a cardboard sheet (paper) on the surface, a corrugated base paper (crepe paper) rolled into a corrugated middle layer, and a linerboard (paper) inside to form a plate shape. Five-layer paperboard is basically the same as three-layer paperboard, except that there is more wavy corrugated paper and a core paper in the middle. Whether the adhesion between the layers of paper sheets is tight and firmly affects the quality of the corrugated cardboard. Well-bonded corrugated board with smooth surface, no blistering, no wrinkle, no warping, no separation between paper sheets after processing into corrugated box, appearance stiff, good compression and cushioning performance, Effectively protect interior contents from being damaged by outside influences.
Corrugated cardboard is made by bonding paper to paper and core paper. Therefore, the state of bonding between the paper and the paper is very important. The bonding of corrugated board is not the stronger the better, but requires the right adhesive force to maintain the normal state of corrugation. If too much adhesive strength is used and excessive amounts of adhesive are used, the roof of the tile will be deformed, and thus the overall strength of the corrugated cardboard will be reduced despite the great adhesion. This requires that in the cardboard production process, grasp the adhesive strength of corrugated cardboard, combined with the actual production conditions, flexible application, reduce costs and produce greater economic benefits.
The determination of the adhesive strength of corrugated cardboard is the use of instruments to test the tightness of the bonding between corrugated paper sheets. The principle is to insert a needle-shaped attachment between the crepe paper and the face paper (or the core paper) of the corrugated cardboard sample, and then apply pressure to the attached sample attachment to make relative movement until the bonding site is separated. It uses the "Newton per square meter" (N/m2) as a measure of the strength of the bond.
The test instrument used for the determination of the adhesive strength of corrugated cardboard shall be a platen compressive strength tester. The size of the press plate shall meet the selected size of the sample so that the sample does not exceed the pressure plate, and the parallelism deviation of the press plate is not greater than 1:1000. The horizontal movement does not exceed 0.05mm, and the moving speed of the dynamic plate is 12.5±2.5mm/min. The test accessories are composed of an upper attachment and a lower attachment, and its role is to apply a uniform external force to each adhesion part of the sample. Each accessory consists of a needle part and a support part that are equidistantly inserted into the space center of the corrugated board, and the parallelism between the needle part and the support part should be less than one percent. The test method is shown in the figure. According to the different positions of the steel needles, they can be divided into two kinds of tests and two tests. The two-sided test of corrugated cardboard was first peeled off on the poor adhesion side, and the adhesive strength on the weaker side could only be measured. Therefore, the two-sided test could not fully measure the adhesive strength of corrugated paperboard, only one-side test. The adhesive strength of both sides of the corrugated cardboard was reliably measured.
The specific test method is as follows:
1. Cut 10 samples of 25mm×80mm unpressed corrugated cardboard from the sample to be tested. The direction of the corrugation is the same as that of the 25mm dimension. The edges of the specimen must be parallel, and the error must not exceed 1mm.
2. Insert the needles into the corrugation between the corrugations. When inserting the needles, do not insert each burr hole. Pay attention to the separation. When separating the crepe paper and the tissue paper, do not separate the paper or the core paper. Insert the upper and lower needles. The parts must be staggered, inserted evenly, and then loaded with supports.
3. Place the attachment with the sample in the center of the lower platen of the tester, start the tester, and press the attachment with the sample at a speed of 12.5±2.5 mm/min until the peak and the paper or the peak is reached. Separation from core paper or liner paper.
4. Record the value displayed on the analyzer with a reading accurate to 1N.
5. The result is expressed as follows:
A = F/S
Where A denotes the bond strength of the sample, expressed in N/m2; F denotes the force (average value) required for the sample to be separated, denoted by N; S denotes the area of ​​the sample, expressed in m 2 or cm 2 .
Several issues that should be noted when measuring the adhesive strength of corrugated cardboard:
1. The speed of the analyzer must be guaranteed to be 12.5±2.5mm/min, too fast or too slow and the speed will cause the measurement result to be different.
2. Cut the sample must be straight, the long side should be perpendicular to the direction of the corrugated.
3. Attachments must have supports, otherwise test errors may occur due to uneven pressure.
4. When inserting the needle attachment, attention must be paid to the separation site, and the adhesive strength of each part is of great significance in the application of production.
5. As a result of the adhesive strength measured using the unsupported (comb) attachment, some may be the tensile strength of the corrugated paper.
The adhesive strength of corrugated board is one of the physical properties of corrugated board. Different from other physical properties of corrugated board, it can better reflect the problems in the production process. Bursting strength and puncture strength are the main indicators of corrugated board. They reflect the physical strength of raw materials and the side pressure strength represents load. These have little relationship with the production process. The corrugated board adhesive strength reflects the tightness of the adhesion between corrugated paperboard sheets. We know that corrugated cardboard is a plate formed by bonding cardboard and corrugated paper processed into corrugated corrugated wads. The processing of corrugated paper into waves is a production process. Bonding linerboard paper and corrugated corrugated paper is also a production process. It can be seen from this that the relationship between the adhesive strength of corrugated cardboard and the production process is very close. In the past, when we measured the physical strength of corrugated board, we often neglected the determination of bond strength. From the standpoint of using corrugated cardboard as a packaging material, it is possible to do so because we consider more of its protective function for the interior goods. However, it is obviously incorrect to ignore the measurement of adhesive strength from the point of view of the production process.
In the production practice, we found that there are mainly the following factors that affect the adhesive strength of corrugated board:
One is the quality of the adhesive. This is the most direct and most direct factor that affects the adhesive strength of corrugated board. Adhesive is made of starch or polyvinyl alcohol and other viscous substances and other chemical substances. Its formulation, production process, and water ratio play a decisive role in the adhesion between sheets. Paste making mistakes lead to instability of paste viscosity. Many carton manufacturers choose adhesives as the main task of QC group activities in the selection of quality control points.
The second is the quality of paper. In addition to the binder as an intermediate medium for bonding, the quality of the paper also has a certain influence on the bonding. The quality of the paper should mainly pay attention to paper moisture, sizing, smoothness (roughness) and so on.
The third is the production environment factor. The environment is too humid, and the initial adhesion speed between the sheets is too slow. When entering the next process, the separation is easy to occur; the environment is dry, the adhesive loses moisture too quickly, the paper sheet has not fully absorbed the adhesive, and also affects the adhesion. strength.
The fourth is equipment and processing factors. Such as corrugated nicks, the surface is not easy to cause local adhesion, uneven roller pressure or lack of speed can affect the quality of corrugated board adhesive quality.
The fifth is the shape factor. Different cocoons have different bonding areas. Within a certain length, the greater the number of turns, the greater the bond area and the greater the strength of the bond.
Sixth, human factors. The amount of paste used in the production depends on the speed of bonding to adjust the amount of paste.
The determination of the adhesive strength of corrugated board can not only understand the quality of corrugated board, but also can be used to control the quality of corrugated board production. When it is found that the adhesive strength of corrugated cardboard is insufficient, it can be analyzed to find out the unfavorable factors to overcome. Among the factors analyzed above, the key is the adhesive. If the paper, environment, shape and other factors change, the adhesive formulation should also be changed accordingly in order to produce a good adhesive corrugated board. Through the determination of the adhesive strength of corrugated board, we can grasp the changes in the bonding quality of corrugated board and timely adjust the preparation of adhesives, so as to achieve the purpose of reducing consumption, increasing output and quality, and enabling production to enter a virtuous cycle. If it is an equipment factor, it is necessary to repair the equipment in time. If it is the impact of speed, it should be adjusted to the appropriate speed. By measuring the strength of the bonding parts of the corrugated board, it is possible to promptly and clearly indicate on which stage a poor adhesion occurs, so that the workshop can timely adjust the production process and improve the process.
By measuring the adhesive strength of corrugated board, we can compare and understand the adhesive effect of different adhesives. At present, a variety of domestic adhesives emerge in an endless stream, and the inventor of each type of adhesive claims that its invention is of high quality and low cost. By testing the sample, you can compare its advantages and disadvantages, and select the most suitable adhesive for your factory. At this time, improving the process, using new materials, and saving costs have great benefits.
In short, in the production process of corrugated paperboard, strengthening the testing of its adhesive strength can timely and accurately obtain relevant information in production. It is very beneficial to use this information to guide production, improve processes, and improve product quality. . This article briefly discusses the determination of the adhesive strength of corrugated board and its application in production. Each company can flexibly use it in combination with the actual situation of the company, and it will be able to produce greater benefits.