Brief introduction of the production process and e

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Introduction to the production process and equipment of polypropylene film

polypropylene film is produced by blow molding, almost all of which are blow down, and the film is introduced into water for cooling. The production process is shown in the figure, which is mainly composed of extruder, head, cooling water ring, traction roller, drying device and coiling device

there are no special requirements for the screw design of the extruder. The sudden change and gradual change compression screws can be used. Based on the principle of obtaining the melt with uniform pressure and temperature, their diameter is 30 ~ 65mm. The length diameter ratio l/d is greater than that of the screw used for polyethylene cans, which is generally 20 ~ 26, and at least more than 20. The compression ratio is 3 ~ 4. The homogenization section should be slightly longer, that is, l1=10d, l2=4 ~ 6D, l3=9~11d

die size depends on extruder capacity and film specification. The film with different specifications can be obtained by replacing the machine head and water-cooled ring. The inflation of polypropylene film is much smaller than that of polyethylene film, generally 1 ~ 2. The structure of the die is mainly cross shaped and spiral

Cooling of the bubble tube is an important step in blowing polypropylene film. Polypropylene is a kind of high crystalline resin. The transparency and physical properties of the film are very different due to different cooling conditions after extrusion. It cools slowly to form monoclinic system with high crystallinity, spherulites increase and will dissolve into metal. The sheath is made of pc-pbt mixture makroblend with strong impact resistance into the mold. Therefore, the transparency is poor and the film is brittle; Rapid cooling, less monoclinic crystals, more hexagonal crystals, and smaller lattice, so the film is transparent. At present, the recent price of MNP powder on the platform is about $78.8, which is high and feels good

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