The bag breaking rate is high, and the culprit is actually it.

The heat sealing temperature has the most direct influence on the heat seal strength.

The unevenness of the melting temperature of various materials directly determines the minimum heat sealing temperature of the composite bag. In the production process, due to various effects such as heat sealing pressure, bag making speed and thickness of the composite substrate, the heat sealing temperature selected in practice is usually higher than the melting temperature of the heat sealing material. The lower the pressure of the heat seal, the higher the heat sealing temperature is requested; the faster the machine speed, the thicker the surface layer data of the composite film, and the higher the heat sealing temperature requested.

If the heat sealing temperature is lower than the softening point of the heat sealing material, it is impossible to completely seal the heat sealing layer regardless of how to increase the pressure or extend the heat sealing time. However, if the heat sealing temperature is too high, it is easy to damage the heat sealing material at the welding edge and melt and extrude, resulting in a "root cutting" scene, which greatly reduces the heat sealing strength of the sealing and the impact resistance of the bag.

The variety, thickness and quality of the heat seal layer have a decisive influence on the heat seal strength

Commonly used heat sealing materials for composite packaging are CPE, CPP, EVA, hot melt adhesives and other ionic resins co-extruded or blended modified films. The thickness of the heat seal layer material is usually between 20 and 80 μm, and in particular, it is also 100 to 200 μm.

With the same heat sealing material, the heat seal strength increases as the heat seal thickness increases. The heat seal strength of the retort pouch is usually requested to be 40 to 50 Newtons, and therefore, the heat seal material thickness should be 60 to 80 μm or more.

To reach the heat seal strength of the ambition, the necessary pressure is essential

With regard to the thin and light packaging bags, the heat sealing pressure should be at least 2 kg/cm 22 and increased correspondingly with the addition of the total thickness of the composite film. If the heat sealing pressure is insufficient, it is difficult to achieve true fusion between the two layers of film, and the partial heat sealing is not good. It may be difficult to catch the bubbles trapped in the center of the weld to form a virtual weld.

Of course, the heat sealing pressure is not as large as possible. It should be done without damaging the weld edge. Because of the high heat sealing temperature, the heat sealing material of the weld edge is already in a semi-melted state, and too much pressure is easy to squeeze away. The heat sealing material makes the weld margin constitute a semi-blocking condition, the weld seam is brittle, and the heat seal strength is lowered.

If the welded joint after heat sealing is not well cooled, it will not only affect the flatness of the weld, but also have a certain influence on the heat seal strength.

The cooling process is to shape the weld just after heat sealing with a lower temperature under a certain pressure to eliminate the process of stress gathering. Therefore, the pressure is not good, the cooling water circulation is not smooth, the circulation amount is not good, the water temperature is too high, or the cooling is not timely, the cooling is poor, the heat sealing is uplifted, and the heat sealing strength is lowered.

The heat sealing time is mainly determined by the speed of the bag making machine.

Heat sealing time is also a key factor affecting weld seal strength and appearance. The same heat sealing temperature and pressure, the heat sealing time is long, the heat sealing layer is more fused, and the connection is stronger, but the heat sealing time is too long, which easily constitutes the wrinkling of the weld and affects the appearance.

The more heat seals, the higher the heat seal strength

The number of longitudinal heat seals depends on the ratio of the useful length of the longitudinal electrode to the length of the bag; the number of transverse heat seals is determined by the number of sets of the machine's transverse heat seal equipment. Outstanding heat seal, requesting heat seals at least twice. There are two sets of hot knives for a typical bag making machine, and the higher the degree of stacking of the hot knives, the better the heat sealing effect.

Composite film with the same structure and thickness, the higher the peel strength between the composite layers, the greater the heat seal strength

For products with low composite peel strength, the weld damage is usually the first layer peeling of the composite film at the weld, so that the inner heat seal layer independently receives the damage tensile force, while the surface layer data loses the reinforcing effect, and the weld heat seal The intensity is thus greatly reduced. If the composite peel strength is large, no peeling at the weld edge occurs, and the measured heat seal strength is much greater.

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