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[YLTpacking] Reasons and solutions for low peel strength of BOPP/CPP

Reasons and solutions for the low peel strength of BOPP/CPP When BOPP/CPP is compounded without solvent, the phenomenon of low peel strength sometimes occurs. The national standard requires the peeling force to reach 0.6N/15mm. For this structure, it can reach 1.0N/15mm or more in good cases, and sometimes as low as 0.3~0.4N/15mm. At the same time, the complete transfer of ink can be easily observed. However, no delamination was found in the process of heat-sealing the bag. A common situation for this phenomenon is that the BOPP film undergoes its own interlayer peeling during the peeling process. The BOPP film is usually a multi-layer structure. When the bonding strength of the glue between BOPP and CPP is greater than the bonding strength between the different layers of the BOPP film itself, the film will be separated in the weaker place. The measured peel strength at this time is actually not. The bond strength of glue, but the interlayer peel strength of BOPP. This phenomenon can be verified by staining the peeled membranes. There is a glue dye that can dye polyurethane materials and show red, while for films, nylon is khaki, and other films are not. This stain is often used to determine which side of the substrate the glue is on. For the BOPP/CPP composite film, the film is peeled off without breaking the BOPP, and dyed with a dye under certain conditions, the result is that there is no color development on both sides. This situation shows that the peeling place is not the interface of the glue, nor the interface after the transfer of the ink (polyurethane system), because both the glue and the polyurethane ink should show red after dyeing. In this case, the interlayer peeling occurred in BOPP, which can be verified by further experiments. The film that was dyed just now was lightly rubbed back and forth on the CPP-containing side with sandpaper, and then dyed again, and it was observed that the sanded area showed red. This is because after the sandpaper wears off a layer of OPP film, the polyurethane ink is exposed and the dyeing shows red. In addition, for this structure, the angle of the test peel force also has a great influence on the test value. Usually, during the free angle test, BOPP is easy to break, and only the highest value can be read, which can reach 2.0N/15mm or more, or even As high as 4.0N/15mm or more, which is actually the breaking strength of BOPP. At the T-type test angle, BOPP sometimes breaks, and sometimes breaks after a period of plateau value. Compared with the first two methods, 180° peeling is easier to obtain a stable reading, but BOPP is easier to completely peel off the interlayer, and the measured data in this case is low, which is the interlayer peel strength. The quality of the substrate largely determines the final peel test result of this structure. The peeling process is separated from the weakest interface. If the substrate remains unchanged, it is difficult to improve by adjusting the glue or ink. For example, the same BOPP/CPP compound will get similar results whether it is dry compounding or solvent-free compounding. For more detailed knowledge of flexible packaging, please go to: http://www.yltpacking.com

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