The factors affecting the adhesive strength of corrugated boxes are not only present in the carton production process, but also in the carton inspection process. Because the adhesive strength of the carton is high or low, it must be shown by the test results. Therefore, the influencing factors of the detection process cannot be ignored.
1. Sample sampling, pretreatment conditions and the impact of the test environment, according to the requirements of the "procedure", the test sample box should be randomly selected. The performance inspection sample box shall be drawn from the sample box that has passed the inspection of appearance. The 12 samples taken shall be representative. They shall be cut from different parts of the three sample boxes and shall be prepared for each of the six surface inspection blocks. Distinguish the mark, not easy to figure out, only saw the sample from one or two pieces of cardboard, the "Protocol" also stipulates that the sample must be pretreated in 23 ± 2 °C, relative temperature 50 ± 5% environment 24h, and in this condition Under the test.
GB6544 stipulates that after the constant temperature and humidity treatment of the sample, the moisture content should be between 10 ± 2%, if these precautions, conditions and the environment can not meet the standard requirements will affect the accuracy of the adhesive strength test results.
2. The selection of the peeling frame has a great influence on the bond strength value at the time of testing. At present, the peeling rack used by the laboratory to detect the adhesive strength of the carton has two forms: one is a comb stripping rack manufactured by a company in Changzhou (TPN-2 type The stripping rack must be restructured to meet the requirements of the "Regulations"); the other is a stripping rack (WZL-1 type) manufactured by a factory in Sichuan.
As far as the impact of the two on the adhesive strength test results, the former type A and C type pins are too thick, and when the holes are inserted into the corrugated hole, artificial cracks are generated at different levels on the bonded part where the sample is to be tested. Followed by some of the pins will produce bending deformation after a period of time, not parallel to the pressure of the plate surface, so that the sample in the 25mm width direction of unilateral uneven peeling phenomenon.
The latter has a thinner pin diameter (A楞φ3mm, B, C楞φ2mm). After the sample is inserted into the borehole, the pin end is supported so that the pin is not easily deformed after being forced. Therefore, the latter can better overcome the defects of the former.
Sometimes the same batch of samples, using the above two kinds of stripping rack test comparison, the former test of the adhesive strength value than the latter's lower 5 to 10%, if the pin deformation is large, the result is greater. Therefore, regardless of which type of stripping frame is used, the deformation of its pins must be prevented.
3. When the test results are converted, the effect of the number of turns on the sample on the bond strength value is stipulated in the “Regulations†5.2.7. The test and calculation methods are performed according to GB6548, while the 6.4 results in GB6548 are incorrect. That is, A=F/S, A-bonding strength, N/m (precisely N/m楞), maximum force required when F-samples are all separated, N; S-sample area, cm2 . Obviously, the units on both sides of the equation do not match, that is, N/m楞≠N/cm2, and the concept does not hold.
The “Regulations†did not give correct calculation formulas. Actually, people perform calculations according to the methods described in some books or training courses. For example, in “Corrugated Paper Box Test Methodâ€, the bond strength formula is: A= F/0.025 × number of turns, or A, F notes in the same as in GB6548, number of turns on a sample. Therefore, there are two cases of the number of corrugations: one is to take the number of full (complete) turns on the sample; the other is to take only the actual number of peeled turns in the sample.
In the same sample, the number of turns of the latter will be one to two less than the former, which means that when the same test value is converted to the bond strength value, it will be larger due to different values ​​of the number of turns. The difference is directly related to the evaluation of the bonding strength of a batch of carton.