In the bag making process of flexible packaging production, the main factors affecting the heat sealing quality are heat sealing temperature, heat sealing time and heat sealing pressure.
1. Heat sealing temperature
If the heat sealing temperature is too high, the film will overheat and decompose, the thermal deformation will increase, and the heat sealing strength will decrease; however, if the heat sealing temperature is too low, the film will not melt and the heat sealing strength will be low. The heat sealing temperature is mainly determined by the melting point of the material. The melting point of the material is high, so is the heating temperature, and vice versa. Hot plate welding is the most common method. Hot plate welding is to use electric heating method to make the welding mold reach a certain temperature, so as to melt the film under a certain pressure and weld. The three factors of heat sealing are heat sealing temperature, heat sealing pressure and heat sealing time.
The heat sealing temperature of the composite film should be determined according to the heat sealing temperature of the inner heat sealing layer material. However, it should be noted that the heat sealing temperature should not be higher than the setting temperature of the outer layer of plastic film, which will damage the heat setting of the outer bi-directional tensile film, thus causing the pocket to shrink after heat sealing. However, the higher the heat sealing temperature is, the better the heat sealing strength is. The lowest heat sealing temperature should be above the softening point of the inner layer material, and the best temperature should be 15-30 ℃ above the melting temperature, but lower than the decomposition temperature.
2. Heat sealing time
The heat sealing time is usually between 0.5 and 1 second. When welding the hot plate, a piece of high temperature resistant silicon cloth should be padded on the hot plate, and the high temperature resistant silicon cloth should be fixed on the heat sealing frame of the bag making machine with screws. The heating time is related to the thickness and temperature of heat sealing material. If the thickness of the material is large and the heat sealing temperature is low, the heating time should be appropriately prolonged; otherwise, the heating time should be shortened. For the heat shrinkable film and the final stretching film, the heating time should be shortened as far as possible in order to reduce the shrinkage deformation during heat sealing. For thermosensitive plastics (such as PVC), the heating time should be shortened to prevent thermal decomposition.
3. Heat sealing pressure
The pressure of heat sealing is installed on the bag making machine and can be adjusted properly. If it is not adjustable, it is generally 19.6n/cm2. If the heat sealing pressure is too high, the film of the heat sealing part will be thinned and the strength will be reduced. However, the heat sealing pressure should not be too small, otherwise, the heat sealing strength will become worse because of the light pressure and the melting layer can not be fully mixed.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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