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The three elements of heat sealing bag making
Traditionally we call heat sealing temperature, heat sealing time, heat sealing pressure for heat sealing bag making three elements.
1. Heat sealing temperature
The effect of heat sealing temperature is to make glue layer heated to an ideal state of viscous flow.
Due to determine the melting point of polymer is not, is a melting temperature range, i.e. there is a temperature between solid phase liquid region, when heated to the temperature area, membrane into the molten state. Polymer viscous flow temperature and decomposition temperature of the heat sealing lower limit and upper limit, the size of the viscous flow temperature and decomposition temperature difference value is an important factor to measure the heat sealing is difficult.
Heat sealing temperature is according to the characteristics of heat sealing materials, film thickness, the number of hot heat sealing pressure and heat sealing area size and Settings. Same parts stamping pressure increase, the temperature can be appropriately reduced, heat sealing area is large, the temperature can be slightly higher.
In the process of heat sealing compound bag, heat sealing temperature on heat sealing strength most directly, the influence of melting temperature of various materials, directly determine the minimum heat sealing temperature compound bag. In the actual production process, heat sealing temperature heat sealing pressure, bag making machine speed and complex factors such as the thickness of the base material, so the actual heat sealing temperature tend to be higher than the melting temperature of the heat sealing materials. If the heat sealing temperature is lower than the heat sealing material softening point, no matter how to increase the pressure or extend the time of heat sealing, all can't make real sealing heat sealing layer. In general, with the increase of heat sealing temperature, heat sealing strength also increases, but at a certain temperature, the strength will not increase (see figure 1) the relationship between heat sealing strength and temperature. If heat sealing temperature is too high, easy to damage the welding heat sealing materials, the melt extrusion "root" phenomenon, greatly reduces the sealing heat sealing strength and impact resistance performance of the compound bag.
Heat sealing time of 2.
Heat sealing time refers to the time duration of the film in a hot sword, it is also affecting the heat seal strength and the appearance of a key factor. The same heat sealing temperature and pressure, heat sealing time is long, the heat sealing layer fusion, more fully combined with stronger. But the heat sealing time is too long, easy to cause heat sealing seam wrinkle deformation, affect the flatness and appearance; Heat sealing time is too long, at the same time also can cause macromolecular decomposition, worsen the sealing interface sealing performance.
In general heat sealing time is mainly determined by the speed of bag making machine. The old bag making machine, adjust the heat sealing time only by changing the speed of bag making machine, to extend the time of heat sealing, it must sacrifice the production efficiency. At home and abroad in recent years, bag making machine manufacturers use independent variable frequency motor control heat sealing knife down and feed technology, enables bag making machine without changing bag making speed under the condition of independent adjust heat sealing time or in control under the condition of invariable heat sealing time independent adjust the bag making speed, greatly facilitate the bag making machine operation and quality control, improves the production efficiency of bag making machine.
3. Heat sealing pressure
The function of heat sealing pressure is to have been under a state of viscous flow of polymer resin film on the heat sealing interface between effective molecular mutual penetration, diffusion, so as to achieve a certain heat sealing effect.
To achieve the ideal heat sealing strength, must be the appropriate pressure. For general thin medicine packaging, hot sealing pressure to at least 20 N/cm2, and with the increase of total thickness of composite film or heat sealing width increases, the required pressure should also be increased accordingly. Jorge sealing pressure is insufficient, between two layers of plastic film heat sealing material is difficult to achieve the real joint and mutual fusion, lead to local heat sealing, or difficult to eliminate the heat sealing layer in the air, in the virtual or uneven.
But when the heat sealing pressure is too large will produce the phenomenon of molten material extrusion, squeeze out some of the heat sealing material, the weld edge forming half cut off state, and the weld crisp, influence the heat sealing effect, reduces the heat sealing strength. After the general heat sealing, the sealing parts strength losses shall not be greater than 10% ~ 10%.
The change in pressure can change the heat sealing properties. Obviously, the greater the pressure, heat sealing time required or heat sealing temperature can be reduced, but at the same time the heat sealing range will be narrowed. Practice is can adjust the pressure, the use of high temperature operation, to increase production by reducing heat sealing time, but control is difficult to operate, and must be especially careful, lest produce negative effects.
Composite membrane materials themselves
In addition to the three elements of heat sealing bag making a greater influence on the process parameters on the bag, the performance of the composite material is also the most direct impact on the technical specifications of the heat sealing bag making equipment operation parameters in the process of the bag and one of the important factors.
Dongguan RUIZHE packing products co., LTD., founded in 1998, is committed to the production of soft rubber products: PVC (material can pass EN - 71, ROHS, REACH 15 p, 6 p, such as testing standard), TPU, OPP compound bag, etc. Welcome to inquire