In roll-to-roll processing, there is very confusion when it comes to “fluid coating” and “extrusion coating”. Both the terms are used if you are dealing with Paper Extrusion Coating Laminating Machine. These terms fluid coating and extrusion coating, both refer to applying a fluid to a substrate. To understand the difference between them, these are discussed separately in the following:
The fluid in a fluid coating operation can be heated or room temperature. The fluid is pushed from a fluid tank to the covering head and distributed across the substrate. Then the fluid is healed through the application of some energy type, such as ultraviolet light, oven heat, etc. The ultimate construction is a cured fluid in a coating application either on a film, paper, or foil. It is just like a roll of tape
The fluid in the case of the extrusion coating application is an extruded polymer. The pellets of this polymer in an extruder are compounded and handled to the extrusion coating die. The extrusion die in the coating is placed above a substrate and the polymer fluid is cast onto the film, paper, or any foil to form a thick film. This coating is just like wax-coated paper.
The main difference between fluid coating and extrusion coating begins at the handling of the raw material. In the fluid coating operation, the liquid is pumped. On the other hand, when it comes to extrusion coating operation, the liquid is compounded. In a fluid coating operation, the liquids can profit from compounding elements to transport in an extruder before the coating head. In the process of the lamination layers, the difference is cleared. In this process, you have a multilayered package that starts with a substrate of paper, then the second is polyethylene (PE), and the third one is the foil.
With the fluid coating, the paper is coated with adhesive, cover the foil with glue, and sandwich the polyethylene by a nip. When it comes to extrusion coating, it cast a polyethylene film to the paper and the foil directly at a nip operation. In the end, the structure is the same functionally, but the process involved is different drastically. The extrusion-coated packages have paper and foil, with the layer of polyethylene which acts as the tie-layer. Moreover, the adhesive-coated packages have paper, foil, and substrates of polyethylene, the two adhesive coverings act as two tie-layers.