The plastic packaging bags we use are all heat-sealed, but there are many heat-sealing methods for plastic packaging bags. Common methods are manual heat-sealing, high-frequency heat-sealing, hot-plate heat-sealing, and pulse heat. Sealing method, ultrasonic heat sealing method, infrared radiation heat sealing method, hot air heat sealing method, etc. Each heat sealing method has different advantages and effects. If we want to buy the right plastic packaging bag, we can also grasp the heat sealing method. The following editor will talk to you about how many kinds of plastic packaging bag heat sealing methods?
1. The simplest heat sealing method Manual heat sealing method: commonly used for PE, PP single film heat sealing.
During heat sealing, the edge of the common electric iron blade needs to be bent into an "L" shape with the help of a heat-resistant film. The width of the blade is generally 3mm, and then the wire is connected to the voltage regulator for constant temperature control. If the film has an edge at the seal, the heat seal strength will be greater. In actual operation, it is best to lay 2 layers of fine flat cloth, and then lay a layer of khaki that is not deformable. Strengthen the structure of the pattern (which plays the role of supporting the bones and bones) to achieve the purpose of inter-molecular penetration and improve the sealing of the sealing interface.
2. High-frequency heat sealing method: the high-frequency electric field generated by the self-excited oscillator of the electron tube is used to make the plastic medium molecules generate heat, and a certain pressure is applied to achieve heat sealing.
Under the action of a high-frequency electric field, polar molecules are arranged in the opposite direction to the electrode. The positive charge in the molecule turns to the negative electrode, and the negative charge turns to the positive electrode. If the direction of the electric field changes, the charge will also change position. This displacement of charge is called "polarization". "Polarization" refers to the regular orientation of molecules. To this end, it is necessary to overcome frictional resistance and consume a certain amount of energy, and this energy consumption is converted into heat and released, which is the reason for heat generation. The hot film can be combined under the proper pressure of the bottom plate and the mold.
3. The hot plate heat sealing method of relying on external heating to achieve heat sealing: first put the two overlapping films between two heated (or one of the heated) metal plates until the surface layer is melted, and then make the melted under pressure The surfaces are quickly joined together and the pressure is maintained until it cools. The hot plate heat sealing device has a simple structure, low cost, long life, and is not easily damaged.
4. Pulse heat sealing method: First, the heat-sealed part is melted under pressure, and then cooled and released the pressure. Usually, a nickel-chromium band is used as a heating element instead of a metal plate, and instantaneous current is passed from the nickel-chromium band to heat. During operation, the overlapped plastic film is placed on the workbench, and the heating element above is pressed against the plastic film by manual or automatic control. At the same time, the current automatically flows into the nickel-chromium belt, so the strong thermal energy pulse acts on the thermal cover, which lasts for a long time. After a short time, the current is cut off by the time relay, and then it is cooled, then the pressure is removed, and then the heat seal is removed.
5. Ultrasonic heat sealing method: the main component of the heat sealing machine is a transducer, a coil is wound on the transducer, and the coil is connected to the oscillator. With the help of the magnetostrictive effect, the high-frequency current is converted into mechanical vibration. Emitted outwards, and then transmitted to the film in the form of a wave, causing an effect force inside the film, and forming a collision phenomenon of two layers of films on the vibrating interface. As the heat and temperature rise, the film is softened and melted, and the reaction force of the lower support table and the clamping force of the vibrating head make the polymer molecules on the heat sealing surface diffuse to each other. Therefore, the molecules of the heat-sealed film have a strong binding force.
In addition, there is a hot air heat sealing method. This method is to use hot air to blow it onto the surface of the plastic film for heat sealing. This method can be applied to heat sealing for heavy packaging.