OEM Package Small Flat Silver Zip Lock Mylar Foil Square Bottom Food Bag,

Three quality problems often appear in custom stand up pouches, which are bag leakage during use, uneven bag shape during bag making, and asymmetric bottom seal.

Leakage of Vertical Bag

The leakage of stand-up zipper pouch is mainly due to the selection of composite materials and heat seal strength. The material selection of vertical bag is very important to prevent leakage, whose purpose is to improve the peel strength between the outer layer and the middle barrier layer, the barrier layer and the heat seal layer, and the heat seal strength of the bag. Therefore, the surface tension of the composite surface of the plastic packing film must be greater than 38dyn / cm and the surface tension of the inner heat seal film must be less than 34dyn / cm. Besides, you should choose good ink, high solid content, low viscosity adhesives, and high purity organic solvents.

Heat Seal Strength

Low heat seal strength is also one of the important factors affecting the leakage of standing pouches custom, so professionals should adjust the matching relationship between heat seal temperature, heat seal pressure, and heat seal time, especially pay attention to explore the heat seal temperature of bags with different structures. Because the melting point of different kinds of plastic film is different, its heat sealing temperature is also different; the heat sealing pressure should not be too large and the heat sealing time should not be too long, so as to avoid macromolecular degradation. The heat sealing layer is sheared by the heat sealing knife in the high temperature melting state, which reduces the sealing strength. Besides, the four-layer sealing part at the bottom of the recyclable stand up pouch is the most critical part and the heat sealing temperature, pressure, and time can be determined only after full test verification.

In the actual production process, the leakage test should be carried out according to the different requirements of the contents. The most simple and practical method is to fill a certain amount of air into the bag, heat seal the bag mouth, put it into the basin containing water, and squeeze different parts of the bag by hand. If there is no bubble escaping, it means that the bag is well sealed; otherwise, the heat seal temperature and pressure of the leaking part should be adjusted in time. The custom printed stand up pouch with liquid inside should be treated more carefully.

Uneven Bag Shape

Flatness is one of the indexes to measure the appearance quality of packaging bags. In addition to material factors, the flatness of plastic standing pouch is also related to heat seal temperature, heat seal pressure, heat seal time, and cooling effect. Too high heat sealing temperature, too high heat sealing pressure, and too long heat sealing time will cause shrinkage deformation of the composite film.

Poor Symmetry

Symmetry not only affects the appearance of transparent stand up pouch but also affects its sealing performance. Improper control of the bottom material tension will cause the deformation of round holes on the bottom surface or wrinkles due to the mismatch with the main material tension, resulting in the decrease of heat seal strength. When the round hole of the bottom material is deformed, it is necessary to reduce the discharging tension properly and increase the waiting time for correction during heat sealing, so as to make the intersection of the four layers of the bag bottom fully heat sealed. The emergence of special-shaped bags and stand up zip lock bags has brought new economic growth highlights to the flexible packaging industry.

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