Corrugated carton adhesive strength, also known as peel strength, it is a key physical quantity reflecting the quality of the corrugated board adhesive quality. Good adhesion quality can improve the physical properties of corrugated box such as compressive strength, side pressure strength and puncture strength. Therefore, the bond strength test and adhesion quality analysis become the core part of the corrugated box inspection. At present, there are a series of problems in standards, methods, and data processing in this area. The author believes that it is necessary to study, discuss and unify this understanding so as to ensure that the quality of corrugated boxes is judged correctly or not.
1. Definition of adhesive strength and calculation The adhesive strength of corrugated box refers to the maximum separating force that can be endured by the bonding surface formed by the surface paper, liner or core paper and the corrugation after the corrugated cardboard is bonded.
According to the provisions of GB6548-86, its calculation is shown in formula (1):
P=F/S (1)
Among them, P-bonding strength, N/m2;
The maximum force required to completely separate the F-sample, N;
S-sample area, m2; General S = 2.5CM x CM
(2.5CM dimension line is corrugated).
The bond strength value calculated from the formula (1) essentially means the separation force required to strip the corrugated cardboard per unit area.
According to the provisions of GB5034-85, the bond strength should be calculated as shown in formula (2): P'=F/(L,n) (2)
Among them, P'-bond strength, N/M.
L-sample specimen length, M;
n - The number of watts contained in the specimen, 楞.
The bond strength obtained by the formula (2) substantially means the separation force required to peel a single corrugated fiber in a unit length of the corrugated cardboard.
In actual tests, it was found that the same kind of corrugated cardboard with the same area was peeled off (refers to the shape, adhesive, production process, and the same paper). If the 楞 type is different, the required separation force F is different, so if according to the formula ( 1) Calculate that the resulting bond strength value P has a large gap, that is, P(A)<P(C)<P(B) for three types of A, C, and B types. The reason why the above phenomenon occurs is that the corrugated paperboards of the same type of A, C, and B are three kinds of corrugated paperboards. The density of corrugated sheets increases sequentially, and the sample area S is the same, but the number of corrugated files, n, increases sequentially, that is, corrugation. The number of binding sites between the peak and the tissue (either liner or core paper) increases gradually, so that the separation force F required for the test also increases sequentially. By comparison, F and n are roughly proportional to each other. Therefore, according to the formula (1), the bond strength is expressed in N/m2. The data lacks comparability, and it is unreasonable for different types of corrugated cardboard. In formula (2), n reflects the change of the corrugated type, F/n eliminates the influence of the change in the enthalpy type on the bond strength data, and thus the calculated bond strength is comparable to that of any enthalpy type. Sex. Therefore, the use of N/M.楞 indicates that the bond strength is more scientific and more reasonable than N/m2, which makes it easier for us to compare the bonding strength of different types of corrugated cardboard. The corrugation density and bond strength values ​​of different corrugated board are as follows: 楞 Corrugated density 楞/30CM Bond strength, N/M, 楞 (KG/10CM.楞) Bond strength N/m2 (KG/10CM)
A 34±2 5.88×102(6) 6.66×104(6.80)
C 38±2 5.88×102(6) 7.45×104(7.60)
B 50±2 5.88×102(6) 9.80×104(10.0)
2. Test principle and method The principle of bond strength testing is to insert the pin attachment between corrugated paper and paper (or paper, paper) and then apply pressure to the sample to make it move relative to it. Corrugated cardboard samples are completely separated. 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. Analysis and judgment of bonding quality Corrugated board, especially double corrugated and three corrugated corrugated board, have different layers and bonding surfaces. During the production process, the processing and conditions of different layers and bonding surfaces are used. Paper quality is often different. Therefore, there must be a gap in the bonding quality. This requires that the different bonding surfaces (single side method) or different layers (double sided method) of corrugated cardboard be peeled separately during testing, and the adhesive strength of each peeling layer is calculated and compared by formula (2). The bonding strength of the bonding surface with the lowest test value represents the bonding strength of the entire corrugated paperboard. By comparing it with the standard value, it can be determined whether the bonding 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.
4. Existing Problems 4.1. The formulation of GB 6548-86 was a decade ago. At that time, the type of corrugated box was basically Type A, but now the type of cardboard box has been diversified towards Types A, B, C or even E. Therefore, the method and unit for calculating the bond strength in this standard cannot meet the requirements for carton inspection.
4.2, according to the provisions of GB-6548: F is the separation force required for the sample is completely separated, n is the number of turns contained in the sample, and due to the limitations of the test means, the actual test is stripped open the number of turns is at most n- 1. This has little effect on the situation where the bond strength value is very high or obviously unsatisfactory, but it has an essential effect on the case where the bond strength is between the pass and fail edges. Therefore, I think that the formula (2) should be revised to P'=F/L.(n-1) is more scientific.
4.3, subjective judgments during the test, only to make a combination of peeling off the surface or layer, so that the test results lack comprehensiveness.
4.4. Although attention was paid to peeling between different bonding surfaces or layers, the weighted average of the test data of the peeling surfaces resulted in a lack of scientific results. In fact, only the test data of the same peeling surface could be weighted and averaged.
4.5 Since bonding strength is expressed in units of N/m2 or kg/10m2, it is easy to understand, so it has long been used in production and testing. However, if no 楞 type is specified, the test data loses comparability. In addition, many people mistakenly believe that the kg/10m2 and kg/10m. are two equivalent units, and compare the test value in kg/10m2 with the standard value in kg/10m. .
4.6, confusing the concept of the relationship between adhesive strength and adhesive quality, focusing on the judgment of whether the adhesive strength is acceptable, and ignoring the in-depth observation of the peeled sample, mistakenly believe that the higher the adhesive strength, the adhesive The better the quality, the lack of a comprehensive understanding of the various factors affecting the bonding quality, which is detrimental to the improvement of the bonding process and the improvement of the bonding quality. Therefore, the key to the above problems is the standard aging of the bond strength measurement method, and other relevant standards are not uniform. Therefore, it is necessary to revise the standards related to bond strength testing.
Conclusion In the production of corrugated boxes, adhesives, amount of glue, corrugating rolls, corrugated shapes, production processes, and paper quality all have an influence on the bond strength value and bond quality. Therefore, we are conducting corrugated carton inspections. At the same time, we must ensure that the test method is correct, the determination criteria are clear, and on the basis of the correct judgment of whether the adhesive strength is qualified, discover and analyze the influence of various factors on the bond quality, in order to guide the corrugated box manufacturers to improve the adhesive quality of the carton. In order to ensure the safe transportation of their loaded goods.
1. Definition of adhesive strength and calculation The adhesive strength of corrugated box refers to the maximum separating force that can be endured by the bonding surface formed by the surface paper, liner or core paper and the corrugation after the corrugated cardboard is bonded.
According to the provisions of GB6548-86, its calculation is shown in formula (1):
P=F/S (1)
Among them, P-bonding strength, N/m2;
The maximum force required to completely separate the F-sample, N;
S-sample area, m2; General S = 2.5CM x CM
(2.5CM dimension line is corrugated).
The bond strength value calculated from the formula (1) essentially means the separation force required to strip the corrugated cardboard per unit area.
According to the provisions of GB5034-85, the bond strength should be calculated as shown in formula (2): P'=F/(L,n) (2)
Among them, P'-bond strength, N/M.
L-sample specimen length, M;
n - The number of watts contained in the specimen, 楞.
The bond strength obtained by the formula (2) substantially means the separation force required to peel a single corrugated fiber in a unit length of the corrugated cardboard.
In actual tests, it was found that the same kind of corrugated cardboard with the same area was peeled off (refers to the shape, adhesive, production process, and the same paper). If the 楞 type is different, the required separation force F is different, so if according to the formula ( 1) Calculate that the resulting bond strength value P has a large gap, that is, P(A)<P(C)<P(B) for three types of A, C, and B types. The reason why the above phenomenon occurs is that the corrugated paperboards of the same type of A, C, and B are three kinds of corrugated paperboards. The density of corrugated sheets increases sequentially, and the sample area S is the same, but the number of corrugated files, n, increases sequentially, that is, corrugation. The number of binding sites between the peak and the tissue (either liner or core paper) increases gradually, so that the separation force F required for the test also increases sequentially. By comparison, F and n are roughly proportional to each other. Therefore, according to the formula (1), the bond strength is expressed in N/m2. The data lacks comparability, and it is unreasonable for different types of corrugated cardboard. In formula (2), n reflects the change of the corrugated type, F/n eliminates the influence of the change in the enthalpy type on the bond strength data, and thus the calculated bond strength is comparable to that of any enthalpy type. Sex. Therefore, the use of N/M.楞 indicates that the bond strength is more scientific and more reasonable than N/m2, which makes it easier for us to compare the bonding strength of different types of corrugated cardboard. The corrugation density and bond strength values ​​of different corrugated board are as follows: 楞 Corrugated density 楞/30CM Bond strength, N/M, 楞 (KG/10CM.楞) Bond strength N/m2 (KG/10CM)
A 34±2 5.88×102(6) 6.66×104(6.80)
C 38±2 5.88×102(6) 7.45×104(7.60)
B 50±2 5.88×102(6) 9.80×104(10.0)
2. Test principle and method The principle of bond strength testing is to insert the pin attachment between corrugated paper and paper (or paper, paper) and then apply pressure to the sample to make it move relative to it. Corrugated cardboard samples are completely separated. 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. Analysis and judgment of bonding quality Corrugated board, especially double corrugated and three corrugated corrugated board, have different layers and bonding surfaces. During the production process, the processing and conditions of different layers and bonding surfaces are used. Paper quality is often different. Therefore, there must be a gap in the bonding quality. This requires that the different bonding surfaces (single side method) or different layers (double sided method) of corrugated cardboard be peeled separately during testing, and the adhesive strength of each peeling layer is calculated and compared by formula (2). The bonding strength of the bonding surface with the lowest test value represents the bonding strength of the entire corrugated paperboard. By comparing it with the standard value, it can be determined whether the bonding 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.
4. Existing Problems 4.1. The formulation of GB 6548-86 was a decade ago. At that time, the type of corrugated box was basically Type A, but now the type of cardboard box has been diversified towards Types A, B, C or even E. Therefore, the method and unit for calculating the bond strength in this standard cannot meet the requirements for carton inspection.
4.2, according to the provisions of GB-6548: F is the separation force required for the sample is completely separated, n is the number of turns contained in the sample, and due to the limitations of the test means, the actual test is stripped open the number of turns is at most n- 1. This has little effect on the situation where the bond strength value is very high or obviously unsatisfactory, but it has an essential effect on the case where the bond strength is between the pass and fail edges. Therefore, I think that the formula (2) should be revised to P'=F/L.(n-1) is more scientific.
4.3, subjective judgments during the test, only to make a combination of peeling off the surface or layer, so that the test results lack comprehensiveness.
4.4. Although attention was paid to peeling between different bonding surfaces or layers, the weighted average of the test data of the peeling surfaces resulted in a lack of scientific results. In fact, only the test data of the same peeling surface could be weighted and averaged.
4.5 Since bonding strength is expressed in units of N/m2 or kg/10m2, it is easy to understand, so it has long been used in production and testing. However, if no 楞 type is specified, the test data loses comparability. In addition, many people mistakenly believe that the kg/10m2 and kg/10m. are two equivalent units, and compare the test value in kg/10m2 with the standard value in kg/10m. .
4.6, confusing the concept of the relationship between adhesive strength and adhesive quality, focusing on the judgment of whether the adhesive strength is acceptable, and ignoring the in-depth observation of the peeled sample, mistakenly believe that the higher the adhesive strength, the adhesive The better the quality, the lack of a comprehensive understanding of the various factors affecting the bonding quality, which is detrimental to the improvement of the bonding process and the improvement of the bonding quality. Therefore, the key to the above problems is the standard aging of the bond strength measurement method, and other relevant standards are not uniform. Therefore, it is necessary to revise the standards related to bond strength testing.
Conclusion In the production of corrugated boxes, adhesives, amount of glue, corrugating rolls, corrugated shapes, production processes, and paper quality all have an influence on the bond strength value and bond quality. Therefore, we are conducting corrugated carton inspections. At the same time, we must ensure that the test method is correct, the determination criteria are clear, and on the basis of the correct judgment of whether the adhesive strength is qualified, discover and analyze the influence of various factors on the bond quality, in order to guide the corrugated box manufacturers to improve the adhesive quality of the carton. In order to ensure the safe transportation of their loaded goods.