Analysis of Corrugated Box Adhesive Strength Test and Bonding Quality (Part 2)

2. Test principle and method

The principle of bond strength test is to insert the pin attachment between the corrugated paper and the paper (or paper, paper) and then apply pressure to the sample to make it move relative to each other, resulting in complete separation of corrugated paper samples. . Currently, accessories for adhesive strength testing are unilateral and bilateral. Therefore, the test method is also divided into a single-sided method and a double-sided method.

The single-sided method inserts the upper and lower needle attachments into the same side of the single-layer corrugated sheet in sequence, and the test data reflects the adhesive strength of the bonded sheet. In the double-sided method, the upper and lower needle attachments are inserted into the opposite side of a single-layer corrugated sheet, and both sides of the same Iridium layer are peeled at the same time during the test. The side with poor adhesive strength is first separated from the peak, and the test data reflect The bonding strength of the bonding surface with poor bonding strength of the same ruthenium layer.

Comparing the two methods can be found: the single-sided method needs to peel off each combination surface of the corrugated paperboard, which is cumbersome. It is suitable to analyze the bonding strength of each bonding surface. The double-sided method is relatively simple, and it is easy to find joint surfaces with poor adhesive strength, but it does not reflect the adhesive strength of each joint surface. It is often used to analyze and determine whether the adhesive quality of the entire corrugated cardboard is acceptable.

In addition, in actual tests, it was found that whether the single-sided or double-sided tests are used, the number of genuinely peeled corrugated sheets is at most n-1, that is, at least one peak at the edge of the specimen is only subjected to unidirectional tension. The effect is unbalanced and therefore often cannot be stripped.

3. Bond quality analysis and judgment

Corrugated paperboards, especially double corrugated and three- corrugated corrugated paperboards, have different corrugated layers and bonding surfaces. During the production process, the processing and conditions of different corrugated layers and bonding surfaces are often different, so the quality of paper is often different. There must be a gap in quality.

This requires separate peeling of the corrugated board (single-side method) or different layers (double-side method) of the corrugated board during the test. The bond strengths of the individual peeling layers are calculated and compared by Equation (2). The adhesive strength of the bonding surface with the lowest test value represents the adhesive strength of the entire corrugated cardboard. By comparing it with the standard value, it can be judged whether the adhesive strength of the corrugated cardboard box meets the specified requirements.

However, the bond strength value meets the standard requirements and does not mean that the corrugated paperboard has a good bond quality. During the test, attention should also be paid to observe the amount of glue, the width of the glue, the degree of penetration of the adhesive, the shape of the corrugated fiber, and the condition of the napped paper. Comprehensive analysis of the above phenomena and test data to correctly evaluate the quality of the bond.

Practice has proved that: excessively high bond strength does not represent a good bond quality, because the extremely high bond strength, often due to the large amount of glue, glue is too wide, even adhesive into the crucible, causing deformation of the corrugated, Corrugated board is not even, so that the pressure resistance of corrugated board is reduced. Therefore, good bonding quality requires not only that the bonding strength meets the specified requirements, but also that the amount of glue is low, the area of ​​the glue is suitable, and the corrugated paperboard has a good structure.

In addition, when the test bond strength value is low and the release layer paper fiber separation rate is high, the low test data may reflect the fiber binding force of the paper at the time of the test and does not necessarily mean the adhesive quality and the bonding process. There are problems with the production process, which is especially important for production companies. (To be continued)