For plastic raw materials of different materials (such as polyethylene, polypropylene, etc.), when using the SJ film blowing machine, the following adjustments need to be made to ensure production efficiency and film quality:
1. Melt index and die adjustment
Polyethylene (PE)
Melt index (MI): The melt index of PE affects its fluidity and formability. According to the MI of PE, select the appropriate die structure and outlet size to ensure that the melt can be extruded smoothly and form a good film.
Die gap: Adjust the gap of the die to adapt to the melting characteristics of PE to ensure the uniformity of the film thickness.
Polypropylene (PP)
Melt viscosity: The melt viscosity of PP is higher, requiring higher extrusion pressure and more precise die design. The die should have a good flow channel design to reduce the resistance of the melt in the flow channel.
Die structure: Select a die structure suitable for the characteristics of PP to ensure the uniformity and transparency of the film.
2. Temperature control
Polyethylene (PE)
Heating temperature: The melt temperature of PE is usually high, and it is necessary to ensure that the heating system of the film blowing machine can reach the appropriate melt state. According to the melting characteristics of PE, gradually increase the temperature of each zone until the raw material can be evenly melted and stably extruded.
Polypropylene (PP)
Temperature setting: Although the melt temperature of PP is also high, it may be different from PE. Therefore, the heating temperature needs to be adjusted according to the specific melting characteristics of PP.
3. Extrusion speed and pressure
Polyethylene (PE)
Extrusion speed: PE usually requires a higher extrusion speed to obtain good film quality. Therefore, the extrusion speed and pressure of the extruder need to be adjusted to adapt to the extrusion characteristics of PE.
Polypropylene (PP)
Extrusion pressure: Due to the high melt viscosity of PP, a higher extrusion pressure may be required to ensure that the melt can be extruded smoothly. At the same time, the extrusion speed also needs to be adjusted to maintain a stable extrusion process.
4. Cooling system adjustment
Polyethylene (PE)
Cooling efficiency: According to the cooling characteristics of PE, adjust the cooling efficiency and air volume of the air ring to ensure that the film can be quickly cooled and shaped.
Polypropylene (PP)
Cooling control: PP crystallizes faster and requires stronger cooling capacity to control its crystallization behavior. Therefore, the cooling method and air volume of the air ring need to be adjusted to meet the cooling needs of PP.
5. Other adjustments
Bubble control: For plastic raw materials that are prone to bubble generation (such as PP), the bubble control and removal mechanism of the film blowing machine needs to be adjusted to ensure the flatness of the film surface.
Reeling adjustment: Adjust the speed and tension of the reel according to the material and thickness of the film to ensure that the film can be wound flatly and tightly on the mandrel.
