In different packaging publications, many people in the industry have expressed their opinions on the adhesive strength of corrugated cardboard and have benefited greatly from it. During the years of packaging inspection work, we have some understanding and understanding of the bond strength measurement method and product standard on the bond strength index specification, write it out to communicate with peers, in order to make the bond strength test result more scientific, accurate.
(a) The discussion of the definition of the adhesive strength of corrugated board is defined in the national standard GB/T 6548-1998: the needle attachment is inserted between the crepe paper and the facial tissue of the specimen (or between the core papers), and then the insertion test is performed. The needle-like attachment exerts pressure so that it moves relatively until it is separated by the separated portion.
The Swedish Packaging Research Institute's determination of the adhesive strength of corrugated cardboard refers to the use of certain equipment to determine the adhesive strength between the inner face of the corrugated cardboard and the corrugation under certain conditions. They call it the pin type adhesion test PAT. The test method is the same as our national standard.
After many years of carrying out this test, it is believed that the results obtained by the above method are, strictly speaking, referred to as inaccurate bond strengths. When the adhesive force is less than the bond strength between the paper fiber layers, it is possible that the result obtained is sticky. When the combined strength of the paper fibers is less than the bond strength, it is possible to measure the force that breaks the fiber layers. Analysis of the sample state after the test also confirmed this. Some corrugated cardboards are used to peel the corrugated and face paper (or core paper) by hand. It is also considered that the adhesiveness is good by observation and feel, but the force value measured on the press after inserting the needle attachment into the chamber is small. . The test specimens were analysed because the fibreboard of the boxboard or corrugated medium used was not well bonded and the paper fibres were separated instead of the bonded surfaces.
Therefore, we believe that this test is called "peel strength" more appropriate. The purpose of its test is to evaluate the bonding between the corrugated board structure. This can remind people to consider the problem from many aspects. Any problems with the material of the board, the quality of the bonding, etc., will affect the ability of the corrugated-top paper (or core paper) to join, which will affect other properties of the corrugated board. Such as edge pressure strength and carton box pressure and so on. Some problems, which may have been created before, may not be explicit, and various problems may arise after use or for a certain period of time.
(b) Discussion of the results expressed At present, the results of the adhesive strength of corrugated cardboard specified in our standards are expressed in three ways:
(1) A=F/l·n (N/楞·m or kgf/楞·10cm)
(2) A=F/s(N/m 2)
(3) A=F/L(N/m)
In the formula: A———adhesive strength F———the maximum force of the separation sample L———the length of the sample—the length of the sample corrugation (ie the width of the sample)
n——The number of corrugations inserted into the specimen S———The area of ​​the specimen The first type represents the maximum force required to separate the unit from the crepe and the face paper or core paper. The second and third types respectively represent the specimens of the unit area. The maximum force required for a unit length specimen. In fact both represent the force required to separate a sample of a certain size. The unit length is the unit length of a certain width, except that the width is not included in the calculation, so there is a certain conversion relationship between the two. The advantage of using these two methods to express the result is that it can intuitively provide uniform requirements for the adhesive properties of a certain size of corrugated board, no matter what type of tamper. As to how it can be achieved, it is necessary for designers to achieve this by selecting raw materials, adhesives, suitable thorium-type structures, and formulating reasonable process plans and perfect production management. However, these two methods are not uniform in operation, often the size of the sample is constant, and the number of inserted needles is different due to the difference between the corrugated cardboard type or the same type of the different types of equipment. different. Attachments with the same number of needles have different effective lengths after insertion of different types of specimens, so only the details specified in the standard are operability.
We prefer to use N/楞·m to indicate the bonding strength. From the aspect of testing, this method of expression uses no matter how big the sample is, inserting several needles, and the final result is to separate one unit from the other. The force required to express, without too much emphasis on the size of the sample, the number of accessories required. From the aspect of design packaging, such a representation method can calculate the force required to separate a crucible, so that it is easy to analyze what type of crucible a corrugated paperboard subjected to certain strength needs to be designed, and how much glue should be applied to each crucible in order to achieve the desired results. Performance and so on. From the specifications of the product standards, this expression has been used for more than ten years from GB/T5034-1985 "Corrugated Cardboard for Export Packaging" to SNT0262-1993 "Corrugated Cardboard Box for Export Commodity Packaging." During this period, whether it is the accumulation of experimental data or the use of habits, this representation is more mature than other methods. There is a certain basis for the determination of technical indicators for the formulation of product standards. In the international community, countries such as Japan also use such units to express, so there is a certain degree of comparability.
In short, regardless of which method of expression is used, in formulating product standards, it is necessary to consider how to set the indicators scientifically and rationally, so that technical indicators can guide products closer to advanced technologies without causing excessive resources. waste.
(III) Problems in Current Standards The bond strength index specified in GB/T6544_1999 “Corrugated Cardboard†is 588 N/m. We believe that this value is set lower to insert 8 samples of Type A single corrugated cardboard. For example, dividing the 80mm specimen with 47N can reach the standard 588N/m, and reaching 588N/楞·m specified in SN/T0262-1993 can be achieved with 132N. From the actual adhesive effect, the former can not meet the requirements of use. Therefore, the relevant standards-setting department should be established to revise the indicators in the standard as soon as possible, and more tests should be carried out to confirm the indicators, and the standards should be set more reasonable.
Another problem is that the test method standards are not detailed, so that the results of the test are highly uncertain due to different laboratories, different operators, and different standards. In the adhesion strength test method, there is no provision on which adhesive surface of the test sample to measure, and each laboratory has its own different measurement method. It is understood that some use the ready-to-use insert method, which layer is inserted to measure which layer, and some layers are measured, taking the average as a result. Each method has its own drawbacks. It only measures the good side (or bad side) of the adhesive or because the result is reported as the average value. Involved in human factors, consciously select samples to achieve the desired results. Therefore, when formulating test method standards, these issues should be considered thoroughly and specified in detail in order to achieve a unified result.
(D) improvement and development of needle attachments Adhesive strength testing for the needle attachment requirements are very strict, such as the diameter of the needle, the length, the parallelism between the needle and the needle, the parallelism between the board and the board will give the test The results have an impact.
At present, the needle attachments used in our laboratories are fixed needles made in West Germany and Sweden. The advantages are that the metal material has high strength, is not easy to be deformed, and the parallelism between the pins is good, and the measured results are inaccurate. Small; its disadvantage is only applicable to a more standard type, otherwise it can not be completely inserted into the measured flaw. The other is a domestically-made adjustable pin, which has the advantage of adaptability, can be adjusted according to the measured object, but the pin is not adjusted due to frequent adjustments and the pin is not at a level. The result of the first stress is that the measured result is low. If we can combine the advantages of the two, the development of new needle attachments is a new topic.
We know that any measurement result will be subject to error from various aspects. The error of the bond strength test comes from the error of the sample size, the pin-to-needle of the pin attachment, and the parallelism error between the plate and the plate. The accuracy of the pressure tester, the temperature and humidity of the test environment, and the error caused by personnel operations. The test size specified by our country's standard is 80mm × 25mm, and these errors have no small impact on the results measured by such a small sample. In addition, the corrugated board's gluing process determines that the corrugated board's adhesiveness is not as uniform everywhere, and the small-sized test piece cannot represent the full bond quality level of the board. In the United States, with a 150 mm x 25 mm sample, the sample is enlarged, and the influence of the integrated error on it is relatively reduced, so that the inspection accuracy is relatively improved. However, if the sample is large, the specification of the corrugated fiber is strict. If the file type is not standardized, the pin cannot be completely inserted into the sample. In Japan, 85mm x 50mm specimens are used, and the effect of synthetic errors is reduced by increasing the width of the specimens. These can be used for reference.
In actual production, the bonding quality of corrugated paperboard is closely related to the quality and moisture content of the adhesive, the adhered paper, the speed of the production equipment, the ambient temperature and humidity, etc. Any problems in one of the links will cause one side of the corrugated paperboard. Or a certain part of the bond is not good. For example, corrugated paperboard produced by the production line has a different bonding quality from one side of the hot plate to the other, and the single-faced corrugated fiber produced by the single-face machine is a two-step process with core paper. The adhesive used is also different, so the same piece of corrugated paper is used. Cardboard, it may be in different parts, the quality of bonding is very different. In actual use, which part is weak and which part is destroyed first affects the quality of the entire carton. In discussing the standard issues above, we also talked about this issue. For example, it should be stated in the standard that the sample to be inspected should be as representative as possible. The inspection method should be as close as possible to the actual conditions of use. However, I think the best way to solve the problem is to develop new pin attachments, such as the use of double-sided pin attachments, which can insert the pin at the same time into the pinnacle, valley and two face paper or face and core paper. Between the pressure, which part is the weakest and which part is separated first. In practice, after corrugated cardboard is made into a packaging container, it is often damaged from the part where the internal quality is defective, so this method is the closest to the actual test method. Of course, the use of double-sided pin attachments requires a lot of work. At present, only a small number of laboratories have such pins. Therefore, it needs to be developed. The new annex also needs to conduct test verification, collect test data, determine indicators, and formulate corresponding standards to support them.
The above are some of the experiences we have done in the testing of the adhesive strength of corrugated paperboards. We hope that the inspection personnel will have some new thinking in these routine tests done every day, thus making the inspection of packing products more scientific and the data more reliable. Kang Li
(a) The discussion of the definition of the adhesive strength of corrugated board is defined in the national standard GB/T 6548-1998: the needle attachment is inserted between the crepe paper and the facial tissue of the specimen (or between the core papers), and then the insertion test is performed. The needle-like attachment exerts pressure so that it moves relatively until it is separated by the separated portion.
The Swedish Packaging Research Institute's determination of the adhesive strength of corrugated cardboard refers to the use of certain equipment to determine the adhesive strength between the inner face of the corrugated cardboard and the corrugation under certain conditions. They call it the pin type adhesion test PAT. The test method is the same as our national standard.
After many years of carrying out this test, it is believed that the results obtained by the above method are, strictly speaking, referred to as inaccurate bond strengths. When the adhesive force is less than the bond strength between the paper fiber layers, it is possible that the result obtained is sticky. When the combined strength of the paper fibers is less than the bond strength, it is possible to measure the force that breaks the fiber layers. Analysis of the sample state after the test also confirmed this. Some corrugated cardboards are used to peel the corrugated and face paper (or core paper) by hand. It is also considered that the adhesiveness is good by observation and feel, but the force value measured on the press after inserting the needle attachment into the chamber is small. . The test specimens were analysed because the fibreboard of the boxboard or corrugated medium used was not well bonded and the paper fibres were separated instead of the bonded surfaces.
Therefore, we believe that this test is called "peel strength" more appropriate. The purpose of its test is to evaluate the bonding between the corrugated board structure. This can remind people to consider the problem from many aspects. Any problems with the material of the board, the quality of the bonding, etc., will affect the ability of the corrugated-top paper (or core paper) to join, which will affect other properties of the corrugated board. Such as edge pressure strength and carton box pressure and so on. Some problems, which may have been created before, may not be explicit, and various problems may arise after use or for a certain period of time.
(b) Discussion of the results expressed At present, the results of the adhesive strength of corrugated cardboard specified in our standards are expressed in three ways:
(1) A=F/l·n (N/楞·m or kgf/楞·10cm)
(2) A=F/s(N/m 2)
(3) A=F/L(N/m)
In the formula: A———adhesive strength F———the maximum force of the separation sample L———the length of the sample—the length of the sample corrugation (ie the width of the sample)
n——The number of corrugations inserted into the specimen S———The area of ​​the specimen The first type represents the maximum force required to separate the unit from the crepe and the face paper or core paper. The second and third types respectively represent the specimens of the unit area. The maximum force required for a unit length specimen. In fact both represent the force required to separate a sample of a certain size. The unit length is the unit length of a certain width, except that the width is not included in the calculation, so there is a certain conversion relationship between the two. The advantage of using these two methods to express the result is that it can intuitively provide uniform requirements for the adhesive properties of a certain size of corrugated board, no matter what type of tamper. As to how it can be achieved, it is necessary for designers to achieve this by selecting raw materials, adhesives, suitable thorium-type structures, and formulating reasonable process plans and perfect production management. However, these two methods are not uniform in operation, often the size of the sample is constant, and the number of inserted needles is different due to the difference between the corrugated cardboard type or the same type of the different types of equipment. different. Attachments with the same number of needles have different effective lengths after insertion of different types of specimens, so only the details specified in the standard are operability.
We prefer to use N/楞·m to indicate the bonding strength. From the aspect of testing, this method of expression uses no matter how big the sample is, inserting several needles, and the final result is to separate one unit from the other. The force required to express, without too much emphasis on the size of the sample, the number of accessories required. From the aspect of design packaging, such a representation method can calculate the force required to separate a crucible, so that it is easy to analyze what type of crucible a corrugated paperboard subjected to certain strength needs to be designed, and how much glue should be applied to each crucible in order to achieve the desired results. Performance and so on. From the specifications of the product standards, this expression has been used for more than ten years from GB/T5034-1985 "Corrugated Cardboard for Export Packaging" to SNT0262-1993 "Corrugated Cardboard Box for Export Commodity Packaging." During this period, whether it is the accumulation of experimental data or the use of habits, this representation is more mature than other methods. There is a certain basis for the determination of technical indicators for the formulation of product standards. In the international community, countries such as Japan also use such units to express, so there is a certain degree of comparability.
In short, regardless of which method of expression is used, in formulating product standards, it is necessary to consider how to set the indicators scientifically and rationally, so that technical indicators can guide products closer to advanced technologies without causing excessive resources. waste.
(III) Problems in Current Standards The bond strength index specified in GB/T6544_1999 “Corrugated Cardboard†is 588 N/m. We believe that this value is set lower to insert 8 samples of Type A single corrugated cardboard. For example, dividing the 80mm specimen with 47N can reach the standard 588N/m, and reaching 588N/楞·m specified in SN/T0262-1993 can be achieved with 132N. From the actual adhesive effect, the former can not meet the requirements of use. Therefore, the relevant standards-setting department should be established to revise the indicators in the standard as soon as possible, and more tests should be carried out to confirm the indicators, and the standards should be set more reasonable.
Another problem is that the test method standards are not detailed, so that the results of the test are highly uncertain due to different laboratories, different operators, and different standards. In the adhesion strength test method, there is no provision on which adhesive surface of the test sample to measure, and each laboratory has its own different measurement method. It is understood that some use the ready-to-use insert method, which layer is inserted to measure which layer, and some layers are measured, taking the average as a result. Each method has its own drawbacks. It only measures the good side (or bad side) of the adhesive or because the result is reported as the average value. Involved in human factors, consciously select samples to achieve the desired results. Therefore, when formulating test method standards, these issues should be considered thoroughly and specified in detail in order to achieve a unified result.
(D) improvement and development of needle attachments Adhesive strength testing for the needle attachment requirements are very strict, such as the diameter of the needle, the length, the parallelism between the needle and the needle, the parallelism between the board and the board will give the test The results have an impact.
At present, the needle attachments used in our laboratories are fixed needles made in West Germany and Sweden. The advantages are that the metal material has high strength, is not easy to be deformed, and the parallelism between the pins is good, and the measured results are inaccurate. Small; its disadvantage is only applicable to a more standard type, otherwise it can not be completely inserted into the measured flaw. The other is a domestically-made adjustable pin, which has the advantage of adaptability, can be adjusted according to the measured object, but the pin is not adjusted due to frequent adjustments and the pin is not at a level. The result of the first stress is that the measured result is low. If we can combine the advantages of the two, the development of new needle attachments is a new topic.
We know that any measurement result will be subject to error from various aspects. The error of the bond strength test comes from the error of the sample size, the pin-to-needle of the pin attachment, and the parallelism error between the plate and the plate. The accuracy of the pressure tester, the temperature and humidity of the test environment, and the error caused by personnel operations. The test size specified by our country's standard is 80mm × 25mm, and these errors have no small impact on the results measured by such a small sample. In addition, the corrugated board's gluing process determines that the corrugated board's adhesiveness is not as uniform everywhere, and the small-sized test piece cannot represent the full bond quality level of the board. In the United States, with a 150 mm x 25 mm sample, the sample is enlarged, and the influence of the integrated error on it is relatively reduced, so that the inspection accuracy is relatively improved. However, if the sample is large, the specification of the corrugated fiber is strict. If the file type is not standardized, the pin cannot be completely inserted into the sample. In Japan, 85mm x 50mm specimens are used, and the effect of synthetic errors is reduced by increasing the width of the specimens. These can be used for reference.
In actual production, the bonding quality of corrugated paperboard is closely related to the quality and moisture content of the adhesive, the adhered paper, the speed of the production equipment, the ambient temperature and humidity, etc. Any problems in one of the links will cause one side of the corrugated paperboard. Or a certain part of the bond is not good. For example, corrugated paperboard produced by the production line has a different bonding quality from one side of the hot plate to the other, and the single-faced corrugated fiber produced by the single-face machine is a two-step process with core paper. The adhesive used is also different, so the same piece of corrugated paper is used. Cardboard, it may be in different parts, the quality of bonding is very different. In actual use, which part is weak and which part is destroyed first affects the quality of the entire carton. In discussing the standard issues above, we also talked about this issue. For example, it should be stated in the standard that the sample to be inspected should be as representative as possible. The inspection method should be as close as possible to the actual conditions of use. However, I think the best way to solve the problem is to develop new pin attachments, such as the use of double-sided pin attachments, which can insert the pin at the same time into the pinnacle, valley and two face paper or face and core paper. Between the pressure, which part is the weakest and which part is separated first. In practice, after corrugated cardboard is made into a packaging container, it is often damaged from the part where the internal quality is defective, so this method is the closest to the actual test method. Of course, the use of double-sided pin attachments requires a lot of work. At present, only a small number of laboratories have such pins. Therefore, it needs to be developed. The new annex also needs to conduct test verification, collect test data, determine indicators, and formulate corresponding standards to support them.
The above are some of the experiences we have done in the testing of the adhesive strength of corrugated paperboards. We hope that the inspection personnel will have some new thinking in these routine tests done every day, thus making the inspection of packing products more scientific and the data more reliable. Kang Li
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