What is the stretching process of a biaxially oriented film production line?
DATE：2024/11/15 10:40:31 / READ： / SOURCE：This station
The stretching process of biaxially oriented film production lines (BOPP, BOPET and other materials) is a crucial link in their production process, directly affecting the physical properties of the film and the quality of the final product. The following is a detailed process description of the stretching part in the biaxially oriented film production line:
1. Preheating
Before stretching, the film material needs to undergo preheating treatment. This process is usually carried out under the action of a heating roller or infrared heater, with the aim of bringing the film to a certain temperature, thereby reducing its viscosity and increasing its stretchability. By heating, the molecular chain structure activity of the film is enhanced, laying the foundation for subsequent stretching.
2. Longitudinal stretching
After preheating, the film enters the longitudinal stretching stage. This process is usually carried out through a specialized longitudinal stretching device between two rollers of different speeds. The film is sandwiched between rollers and then moves rapidly on one side while moving relatively slowly on the other side, causing the film to stretch along its longitudinal direction. During this process, the thickness of the film will decrease while the length will increase. Longitudinal stretching usually significantly improves the strength and toughness of the film.
3. Cooling
After the longitudinal stretching is completed, the film will go through a cooling zone to ensure that the film maintains its new shape and solidifies its molecular structure after stretching. This cooling process helps to lock the orientation state of the molecular chains and prevent the film from shrinking during subsequent processing.
4. Horizontal stretching
The cooled film will enter the transverse stretching stage. The purpose of this stage is to further enhance the mechanical properties and dimensional stability of the film. Similar to longitudinal stretching, transverse stretching also typically uses two sets of rollers at different speeds to stretch the film in the transverse direction. During the horizontal stretching process, the width of the film increases and the thickness decreases, which also enhances its strength and transparency.
5. Heat setting
After transverse stretching, the film needs to undergo heat setting treatment. This often relies on the coordination of heating and cooling rollers to maintain the orientation of the film through heating, further improving the thermal stability, dimensional accuracy, and surface properties of the film. This step is crucial for ensuring the subsequent processing and performance of the film.
6. Roll up
After heat setting, the film enters the winding process. The focus of this step is to roll the stretched film neatly, ensuring no wrinkles, bubbles or other defects. The winding method and speed should be consistent to prevent deformation or damage to the film during the winding process.
7. Quality inspection
After winding, quality inspection of the film is an indispensable step. Usually, visual inspection, thickness measurement, tensile strength testing and other methods are used to ensure that the film meets the specified technical standards.
Before stretching, the film material needs to undergo preheating treatment. This process is usually carried out under the action of a heating roller or infrared heater, with the aim of bringing the film to a certain temperature, thereby reducing its viscosity and increasing its stretchability. By heating, the molecular chain structure activity of the film is enhanced, laying the foundation for subsequent stretching.
2. Longitudinal stretching
After preheating, the film enters the longitudinal stretching stage. This process is usually carried out through a specialized longitudinal stretching device between two rollers of different speeds. The film is sandwiched between rollers and then moves rapidly on one side while moving relatively slowly on the other side, causing the film to stretch along its longitudinal direction. During this process, the thickness of the film will decrease while the length will increase. Longitudinal stretching usually significantly improves the strength and toughness of the film.
After the longitudinal stretching is completed, the film will go through a cooling zone to ensure that the film maintains its new shape and solidifies its molecular structure after stretching. This cooling process helps to lock the orientation state of the molecular chains and prevent the film from shrinking during subsequent processing.
4. Horizontal stretching
The cooled film will enter the transverse stretching stage. The purpose of this stage is to further enhance the mechanical properties and dimensional stability of the film. Similar to longitudinal stretching, transverse stretching also typically uses two sets of rollers at different speeds to stretch the film in the transverse direction. During the horizontal stretching process, the width of the film increases and the thickness decreases, which also enhances its strength and transparency.
5. Heat setting
After transverse stretching, the film needs to undergo heat setting treatment. This often relies on the coordination of heating and cooling rollers to maintain the orientation of the film through heating, further improving the thermal stability, dimensional accuracy, and surface properties of the film. This step is crucial for ensuring the subsequent processing and performance of the film.
After heat setting, the film enters the winding process. The focus of this step is to roll the stretched film neatly, ensuring no wrinkles, bubbles or other defects. The winding method and speed should be consistent to prevent deformation or damage to the film during the winding process.
7. Quality inspection
After winding, quality inspection of the film is an indispensable step. Usually, visual inspection, thickness measurement, tensile strength testing and other methods are used to ensure that the film meets the specified technical standards.
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