Extrusion coating is defined as a process which is used to coat the thermoplastic material onto a substrate like paperboard aluminum foil, woven fabric, paper, PET, BOPP film etc. Most commonly used resins in this process are various polyolefin such as ethylene vinyl acetate copolymers, polyethylene, ionomers, and polypropylene. For instance, extrusion coated film manufacturer use this process is for improving the features of paper by coating it with polyethylene, making it a better water resistant.
Process of Extrusion Coating
It includes coating of a substrate with precisely metered film of molten plastic. The thin extruded molten film is pulled down onto a substrate and then into the nip which is amidst the pressure rolls and chill roll, below the die. A specific amount of pressure is there in between these two rolls which forces the plastic onto the surface. This surface moves at a speed which is faster as compared to the extruded film and the drawing of film onto the desired thickness. This entire process includes- Extruder, Die, Chrome Plated Chilled Roll, Back Up Roll, and Winders / Unwinders.
Advantages of Extrusion Coating
As a process-
Process of Extrusion Coating
It includes coating of a substrate with precisely metered film of molten plastic. The thin extruded molten film is pulled down onto a substrate and then into the nip which is amidst the pressure rolls and chill roll, below the die. A specific amount of pressure is there in between these two rolls which forces the plastic onto the surface. This surface moves at a speed which is faster as compared to the extruded film and the drawing of film onto the desired thickness. This entire process includes- Extruder, Die, Chrome Plated Chilled Roll, Back Up Roll, and Winders / Unwinders.
Advantages of Extrusion Coating
As a process-
- • Double sided coating to achieve desired properties
- • Solvent / adhesive free
- • Thickness of the coating varies depending on the end use
- • Higher line speeds
- • Provides moisture barrier
- • Avoid direct contact of content to the substrate
- • Provide heat seal-able characteristics
- • Reduces loss of content
Factors Influencing Coating Performance
In the extrusion coating process, various resins is used by the extrusion coated film manufacturers and the entire processing is dependent on various factors that are as follows:
- • Melt Temperature
- • Die Gap
- • Air Gap
- • Chilled Roll Temperature
The resins must have some special characteristics like higher melt index (to ensure better adhesion), free from additives, and ideal amount of antioxidants for extrusion coating. In addition to these, some other characteristics should also be present in the resins; these are reduced neck-in properties and good adhesion to substrate at higher line speeds.