Extrusion coating is a process that applies a thin layer of plastic to materials like paper, textiles, and aluminum foil. The plastic is injected into a slot mold and extruded onto the receiving material, then cooled and compressed. This process creates durable and high-quality products used in everyday applications like packaging. The plastics used are thermoplastic resins, which offer a range of beneficial characteristics like moisture resistance and heat sealing potential. Extrusion coating offers advantages like fast line speeds and variable coating thicknesses, and can create different textures and finishes.
Extrusion coating is a process used to coat materials with a thin layer of plastic using heat and pressure. This process is used to improve the durability and surface quality of paper, textiles, aluminum foil and other plastic products. The coating is applied by pressure injection of molten plastic into a slot mold which extrudes a thin plastic membrane onto a movable sheet of receiving material. The combination is then cooled and compressed to form the final product. Depending on the specific requirements of the job, extrusion coating can be used to coat both sides of the product or also to produce laminates.
Plastic coated products made using extrusion coating techniques are found in a large number of everyday applications. These include coated board and paper products, coated fabrics used for fertilizer bags and a range of packaging materials for chemicals, food and pharmaceuticals. These plastic coatings can be used for purely aesthetic purposes, to increase the life and quality of surface finishes and to produce aseptic packaging materials for sensitive or perishable products.
The extrusion coating process consists of a system of heating and pressurizing the granular plastic similar to that used in injection molding. This feeds a constant stream of pressurized molten plastic to an extrusion head fitted with a narrow slot die. The die extrudes a thin film of plastic onto the substrate or recipient material when pulled from a roll. The coated substrate then passes between a nip roller and a water-cooled chill roller. These two rollers ensure that the plastic coating is of the correct thickness and is cooled to solidify and adhere properly to the substrate.
The plastics used for extrusion coating are thermoplastic resins, such as polyethylene, polypropylene and ethylene vinyl acetate. They enable the substrates used to coat a wide variety of beneficial characteristics, greatly expanding the scope of their use. These include resistance to moisture, a hygienic contact barrier for products, low product mass loss and heat sealing potential. Extrusion coating offers many advantages over other processes, including simple double-sided coating, fast line speeds, solvent and adhesive free coating, and variable coating thicknesses.
The extruded coating processes are flexible and allow for a range of user-defined coating textures and finishes. Substrates can be coated on both sides with ease and laminates consisting of alternating layers of different substrate materials and plastics are possible. The surfaces of the chill rolls can also be textured or embossed to give the coating a matte, glossy or decorative finish.
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