Co-extrusion flexible packaging production process is open, don't look pity!
Co-extruded flexible packaging materials are composed of multiple layers of plastic sheets or films, which are made by a one-step method using two or more plastic resins in a flat extrusion or inflation process. So what are the processes of co-extrusion flexible packaging production process? This article will make a detailed answer!
Co-extruded flexible packaging materials are composed of multiple layers of plastic sheets or films, which are made by a one-step method using two or more plastic resins in a flat extrusion or inflation process. The substrate of the coextruded film is never easy to separate. Each resin is melted in a separate extruder, and then the melt passes through the co-extrusion die and keeps them in uniform layers without mixing. When designing the co-extrusion process, in order to prevent layer-to-layer mixing, the rheology of the polymer should be carefully considered, especially the flow pattern and melt viscosity after the co-extrusion die is the same as the single layer material .
Because there are many materials co-extruded together, if the viscosity between the two polymers is not enough, it will affect the overall adhesion of the final product. That is, the layers may be separated under stress. In this case, it is necessary to add a third material, the adhesive layer, which is essentially a thermoplastic adhesive. By closely bonding the two materials, the adhesive layer maintains the integrity of the multilayer material. The adhesive layer must also be melted in a special extruder and fed into the die as a separate layer. Therefore, many coextruded materials have a three-layer structure, two are plastics, and the third is an adhesive layer as the first two materials. Coextruded films with more than four layers in structure are also very common. For example, if EVOH is included as a barrier layer, it must be sandwiched between two polymers to prevent moisture penetration, so the adhesive layer should be at least five-layer structure. Although the resin melt from a single extruder can feed two or more layers of a co-extruded film structure, each new type of resin in the structure must have a dedicated extruder.
Coextruded films or sheets are widely used in the packaging industry. For example, a pallet elastic outer packaging film with different adhesion characteristics on the inner and outer surfaces; snack food made of a co-extruded brown polyethylene with light protection in an inner layer and a white polyethylene with beautiful outer and inner layers Bags etc.
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