Views: 0 Author: Site Editor Publish Time: 2023-04-11 Origin: Site
Plastics commonly used in extrusion blow molding: low-density polyethylene, high-density polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl acetate copolymer, modified polystyrene, thermoplastic engineering plastics such as polycarbonate, thermoplastic elastomer and other polymers and various blends.
Extrusion blow molding process:
1. Use an extruder to melt thermoplastics and extrude them through the die
2. Clamp the molding that reaches the specified length into the blow mold, and cut off the molding by the upper edge of the mould.
3. Depending on the air inlet on the mold leading to the compressed air, the blown type is bad
4. Keep the pressure in the mold cavity to cool the product and then open the mold to take out the product
What is multi-layer co-extrusion blow molding?
What is multi-layer co-extrusion blow molding? Multi-layer co-extrusion blow molding is to use more than two extruders, melt and plasticize the same or different plastics in different extruders, compound and extrude in the machine head to form a multi-layer concentric compound type Embryo, a technology for manufacturing hollow containers by blow molding.
The basic process principle is the same as that of single-layer product blow molding technology. It's just that the molding equipment uses multiple extruders to plasticize different types of plastics.
The technical key of multi-layer co-extrusion blow molding is to control the quality of mutual fusion and bonding between each layer of plastics. Multi-layer co-extrusion blow molding is a blow molding technology developed to meet the special requirements of certain industries such as pharmaceuticals, food and industry for packaging containers, such as air tightness and corrosion resistance. The following content can help you understand it more deeply.
Advantages of multi-layer co-extrusion blow molding
1.Multi-layer co-extrusion blow molding hollow products are extruded and blown into hollow products by several different raw materials through a multi-layer die head, so as to achieve the barrier performance of the container to carbon dioxide, oxygen or gasoline.
2.Co-extrusion blow molding is used to compound various polymers to form multi-layer containers. By combining the advantages of various polymers, the following goals can be achieved.
3.Improve the barrier performance of the container Improve the strength, stiffness, dimensional stability, transparency, softness, heat resistance, etc. of the container, change the surface properties of the container, and reduce the cost under the premise of meeting the strength or performance.
Applications of Co-Extrusion Blow Molding
(1) Agrochemical bottles
The multi-layer co-extruded high-barrier bottle (COEX) adopts the production process of multi-layer co-extruded blow molding. The multi-layer co-extruded high-barrier bottle (COEX) has good resistance to oil, fat, dilute acid, dilute alkali, and most Solvent and excellent high temperature and low temperature performance, excellent gas barrier, water, oil and odor performance and most solvents.
(2)Food and beverages.
Although the glass bottle is a permanent impermeable container, it is not limited by the August 4th disinfectant and sterile disinfectant. However, co-extruded blow-molded multi-layer bottles are not easy to break, can be extruded, light in weight, and have good impermeability; and can freely design multi-layer structures with different capacities, specifications, and complex shapes, and the combination of each layer And the thickness can also be determined independently, it is an ideal food and beverage packaging products. It can be used as packaging for ketchup, rapeseed oil, jam, milk, orange juice, carbonated drinks, beer, etc.
Multilayer co-extruded bottle products include three-layer combinations, five-layer combinations, and six-layer combinations. There are more plastic bottles with six-layer combinations of general materials. The three-layer bottle with EVOH or PA as the barrier layer has little moisture sensitivity and can be used for food packaging. The three-layer composite bottle of PE/PET/PC has transparent, high-efficiency barrier properties, excellent heat resistance and mechanical properties, and does not use bonding materials, which has attracted widespread attention.
(3)Chemical reagents. Chemical reagents are usually industrial or agricultural chemicals.
It requires that the co-extruded multi-layer product has good barrier properties, high ability to withstand internal pressure, excellent mechanical properties and the ability to withstand the swelling of the inner layer of the product by the contained chemicals. Such products are usually three-layer combination, four-layer combination, five-layer combination, six-layer combination of 5-10L barrels, plastic bottles below 1L, etc. In order to prevent chemical reagents from seeping out of the outside world, the barrier layer (PA, PAN, EVOH) is often placed on the inner wall, and the thickness of the layer should be greater than 0.1mm; HDPE is often used as the base resin, and sometimes PP can be used instead of HDPE resin in consideration of chemical compatibility.
(4) Other aspects. In terms of pharmaceutical and cosmetic packaging, products are often required to have better surface properties, such as antistatic, easy to print, high gloss, scratch resistance, etc. At this time, multi-layer products can use PA as the outer material to provide better surface properties and barrier properties. Three-layer combination and two-layer combination products of two different materials or different colors can be applied to different application occasions. For example, the combination of white/black/white can provide the anti-ultraviolet ability of the product; the combination of new material/recycled material/new material can reduce the cost of the product; the combination of coloring/natural color can make the product colored without polluting the food or pharmaceuticals, etc.