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1. The heat sealing temperature has the most direct impact on the heat sealing strength.

The melting temperature of various materials directly determines the minimum heat sealing temperature of composite bags. During the production process, due to various factors such as heat sealing pressure, bag making speed, and the thickness of the composite substrate, the actual heat sealing temperature used is often higher than the melting temperature of the heat sealing material. The lower the pressure of the heat seal, the higher the required heat seal temperature; The faster the machine speed, the thicker the surface material of the composite film, and the higher the required heat sealing temperature. If the heat sealing temperature is lower than the softening point of the heat sealing material, no matter how much pressure is increased or the heat sealing time is extended, it is impossible to truly seal the heat sealing layer. However, if the heat sealing temperature is too high, it is extremely easy to damage the heat sealing material at the welding edge by melting and extrusion, resulting in a "root cutting" phenomenon, greatly reducing the heat sealing strength of the seal and the impact resistance of the bag.

2. The type, thickness, and quality of the heat sealing layer material have a decisive impact on the heat sealing strength.

The commonly used heat sealing materials for composite packaging include CPE, CPP, EVA, hot melt adhesive, and other ion type resin co extruded or blended modified films. The thickness of the heat sealing layer material is generally between 20 and 80 μ Between m, it can also reach 100-200 under special circumstances μ M's. The heat sealing strength of the same heat sealing material increases with the increase of heat sealing thickness. The heat sealing strength of steaming and boiling bags is generally required to reach 40-50 Newton, therefore, the thickness of the heat sealing material should be between 60-80 Newton μ Above m.

3. To achieve the ideal heat sealing strength, a certain amount of pressure is essential.

For lightweight packaging bags, the heat sealing pressure must reach at least 2kg/cm2, and it will increase correspondingly with the increase 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 thin films, resulting in poor local heat sealing or difficulty in removing bubbles trapped in the middle of the weld seam, resulting in false soldering; Of course, the higher the heat sealing pressure, the better. It is advisable not to damage the welding edge, because at higher heat sealing temperatures, the heat sealing material of the welding edge is already in a semi molten state. Excessive pressure can easily squeeze out some of the heat sealing material, causing the weld edge to form a semi cut state, causing the weld to become brittle and the heat sealing strength to decrease.

4. If the cooling of the weld seam after heat sealing is not good, it will not only affect the appearance flatness of the weld seam, but also have a certain impact on the heat sealing strength.

The cooling process is the process of shaping the weld seam that has just been melted and heat sealed at a lower temperature under a certain pressure to eliminate stress concentration. Therefore, insufficient pressure, poor circulation of cooling water, insufficient circulation volume, high water temperature, or untimely cooling can lead to poor cooling, warping of hot sealing edges, and reduced strength of hot sealing.

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

The heat sealing time is also a key factor affecting the sealing strength and appearance of the weld seam. At the same heat sealing temperature and pressure, if the heat sealing time is long, the heat sealing layer will fuse more fully and bond more firmly. However, if the heat sealing time is too long, it can easily cause weld wrinkling and affect the appearance.

6. The more heat sealing times, the higher the heat sealing strength.

The number of longitudinal heat seals depends on the ratio of the effective length of the longitudinal welding rod to the bag length; The number of horizontal heat sealing times is determined by the number of sets of horizontal heat sealing devices on the machine. A good heat seal requires at least two heat seals. The general bag making machine has two sets of ironing knives, and the higher the overlap of the ironing knife positions, the better the heat sealing effect

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