Polyethylene wrapping film extrusion blow molding process
Apr 28, 2019
The polyethylene wrapping film is made by extrusion blow molding. The raw material is made of polyethylene resin, and it can also be extrusion blow molded with LDPE and LLDPE mixture. The proportion of the raw material type low-density polyethylene (LLDPE) resin accounts for about 1/3.
Polyethylene coated extrusion blow molding is best to use special equipment, which is the plastic extruder. It is required to be a general-purpose screw for extruded PE material with a length to diameter ratio of 20:1 and a compression ratio of 4:1 or 3:1, in order to ensure the plasticizing quality of the raw materials, the barrel process temperature control requirement is that the screw should be controlled by water.
The polyethylene envelope forming mold should adopt a spiral core rod structure. When the screw diameter of the extruder is 90 mm, the die diameter of the molding die is 200 mm, and the die gap is about 1 mm. The inflation ratio is 2 to 3. If the special auxiliary machine is not used, the distance between the forming die and the pulling roller should be no less than 8m to ensure sufficient cooling and cooling of the thick film.
In the process of forming polyethylene film, it is necessary to control the process temperature of each section of the barrel: 130-150 °C for the feeding section, 160-190 °C for the plasticizing section, 190-210 °C for the homogenizing section; the molding die temperature is 190-200 °C. The bubble of the polyethylene coating is cooled by air cooling, and if necessary, the herringbone guide can be changed into a water-cooled herringbone guide to match the cooling of the bubble by the wind ring.
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