After the heat-sealing material is determined, the heat-sealing quality of the composite packaging bag is directly related to the heat-sealing process. Usually the main control is the temperature, pressure and time of the heat-sealing.
Heat sealing theory
composite packaging bag is heat-sealed above the heat-sealing temperature, the plastic film becomes a viscous flow state; and the heat-sealing pressure causes the interpenetrating and diffusing external power between the interface molecules of the plastic film in the viscous flow state; certain The heat sealing time will make the interface molecules of the plastic film penetrate and diffuse as soon as possible, so that the interface disappears and becomes a whole, so it has good sealing.
Heat sealing temperature
The minimum heat sealing temperature of the heat-sealing material depends on the melting temperature of the material. The heat-sealing temperature should be higher than the melting temperature of the heat-sealing material. However, how much higher than it should be considered whether the material to be sealed is a single film or a composite film, the thickness of the film, Technical indicators such as heat sealing pressure and heat sealing speed. Generally, the heat sealing pressure is high; the heat sealing speed is slow; the film thickness is large, the heat sealing temperature can be lower, and vice versa.
Heat sealing pressure
The size of the heat sealing pressure also has a great influence on the heat sealing effect. The heat sealing pressure should be appropriate. When the heat sealing pressure is too low, it is difficult for the two layers of heat sealed material to achieve true fusion, or it is difficult to catch up the gas in the middle of the seal. As a result, local leakage is caused. The heat sealing pressure is too high, and when the heat sealing temperature is slightly higher, the heat sealing knife will easily squeeze the molten material in the sealing seam during heat sealing, resulting in "hot cutting" phenomenon. If it is light, the heat sealing strength of the seal is reduced, and the impact strength of the seal is reduced. Generally, the heat sealing temperature is high; the heat sealing speed is slow; the film material is thinner, and the heat sealing pressure can be smaller, and vice versa.
Heat sealing time
Under the same heat-seal temperature and heat-seal pressure, the longer the heat-seal time, the stronger the interface of the heat-seal layer will be. However, if the heat-seal time is too long, the resin at the seal joint will be easily oxidized, which will reduce the heat-seal effect. At the same time, if the heat sealing time is too long, it is easy to cause wrinkling and deformation of the sealing seam, which affects the appearance and causes leakage of the bag.
summary
In short, different heat sealing materials and different additives are added, as well as different treatment methods (corona, printing), etc. for the composite packaging bags of heat sealing materials, the characteristics of heat sealing materials are different. Choose carefully according to different objects to be packed and packaging process.
Temperature, pressure and time are the three important parameters to determine the heat sealing process. It should be properly determined according to the different heat sealing materials and packaging processes of the composite packaging bag to obtain the best heat sealing effect.
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