Co-extruded composite die

日期:2019/5/8 8:33:31 / 阅读: / 来源:本站

Co-extruded composite die
The co-extruded composite die has multiple manifolds (multimanifold), namely MM mode and feed-block mode, ie FB mode. Generally speaking, the MM method is expensive and difficult to operate, but the thickness of each layer is excellent, and the applicable resin range is wide. It can use heat-sensitive and easily oxidatively degradable PVC and PC resin, which combines different resins in front of the lip of the die. The influence between each other is small, the thickness between the layers can be adjusted, and it is easy to produce a product with high thickness precision. The MM method is easy to use a coat hanger type or a tube type die with less resin retention, and a T-die which has a structure of 4 or more layers, and the upper limit is 5 layers.
The laminar flow of each layer can be combined in the mold, the die and the mold, and the inter-layer peeling strength is large, but the interface between the layers and the layer is easy to be unclear, and the mixing is easy to occur. Because the two different viscosity materials are mixed, the small viscosity will wrap the high viscosity material, which is called encapsulation. When the resin material with a small viscosity is inside, when the material with a large viscosity is outside, a certain distance will flow, and the position will change. That is, the viscosity will be small, and the material with high viscosity will be encapsulated in the inside. Come out, completely the opposite structure. The encapsulation phenomenon is related to the difference in melt viscosity between the two resins, and the distance between the confluence and the time of confluence. The pressure difference between the two melt streams is also related to the encapsulation phenomenon. The biggest disadvantage of the coextruded composite film for this purpose is that the interface between the layers is not clear, and the thickness of each layer cannot be precisely regulated. Since the thickness is achieved by adjusting the rotation speed of the extruder screw, the rotation speed is increased, the extrusion amount is increased, and the thickness is increased, which is obviously difficult to precisely control.
The out-of-mold compounding is completely close to the two melt materials. The airflow during inflation brings the very close materials into contact with each other. Although the encapsulation is eliminated, the peel strength between the layers is obviously better than the in-mold and the mold. The mouth compound is poor, and the die compounding is the best choice. It is close to the exit in the mold, and it can be inflated after leaving the die after the meeting. Therefore, the encapsulation is small and the peeling strength between the layers is also better. Extra-mold composite


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