Views: 0 Author: Site Editor Publish Time: 2023-04-04 Origin: Site
The characteristics of multi-layer co-extrusion blow molding High-barrier hollow products of multi-layer co extrusion blow molding are extruded and blown into hollow products from several different raw materials through a composite die to achieve the barrier of the container to CO2, O2 or gasoline, etc. performance. Co-extrusion blow molding is used to compound various polymers to form multi-layer containers. Integrating the advantages of various polymers, the following goals can be achieved;
1. Improve the barrier performance of the container (such as the permeability of oxygen, carbon dioxide, moisture, fragrance and solvent);
2.Improve the strength, rigidity, dimensional stability, transparency, flexibility or heat resistance of the container;
3.Improve the surface properties of the container;
4. On the premise of satisfying the strength or performance, reduce the cost;
5.Absorb ultraviolet rays;
6.A transparent viewing zone can be formed on the opaque container to observe the height of the liquid in the container
The production of multi-layer blow-molded hollow products is mainly to meet the higher requirements of plastic packaging containers such as cosmetics and food for barrier properties, flame retardancy, weather resistance, heat resistance, internal and external dichroism and three-dimensional effects. For example, a double-layer blow-molded bottle whose outer layer is PVC and inner layer is PE. The outer layer of PVC can provide good barrier properties, rigidity, flame retardancy and weather resistance, while the inner layer of PE makes the bottle non-toxic and safe to the packaging. Excellent chemical resistance.
The types of plastics used in multi-layer blow molding containers and the necessary number of layers should be determined according to the specific requirements of their use. Of course, the more layers of the product, the more difficult it is to manufacture the parison, and the higher the production cost.
Typical applications for multilayer blow molded products are the packaging of milk, natural juices, tea, ketchup, carbonated soft drinks (CSD) and beer. For example, 3-layer containers are used for packaging UHT milk and CSD, while 6-layer containers are used for packaging of juices. The key to multi-layer blow molding is to control the melting and bonding between the resins of each layer.
The structure of multi-layer co-extrusion blow molding products
Most of the layers in the wall of multi-layer co-extruded blow molding products are various polymers, which can generally be divided into three layers (base layer, functional layer, adhesive layer)
1. The base layer; the base layer is the main body of the multi-layer composite structure, and its thickness is large, which mainly determines the strength, stiffness and dimensional stability of the product. The base layer polymers are commonly used in PE and PP, and PVC, PET, PC, PA, EVA, etc. are also used.
2. Functional layer; most of the functional layers are impermeable layers, which are used to increase the service temperature of the product and improve the appearance performance. Commonly used polymers for functional layers are EVOH, PVDF, and PAN. PA, PET, EVA are also useful.
3. Adhesive layer; when the bonding performance between the base layer and the functional layer is poor, an adhesive should be used to bond them. The bonding between the layers in the multilayer container wall is both an important point and a difficult point. Commonly used resins for bonding are; maleic anhydride, acrylic acid or acrylate graft modified PE or PP; directly synthesized polymers.