What Is Co-extrusion Technology?

What is Co-extrusion Technology?

Extrusion is the composition of one or more than one thermoplastic in molten form to achieve a desired shape or shape. The extrusion process is important for combining different polymers and combining for certain applications. The formed merge then goes directly into a custom mold to create the desired shape.

The characteristics of co-extrusion extrusion technology uses two or more plastic materials, melt into liquid at high temperature, and enter a precision die head. The internal flow channel system is designed to combine the melt and glue, and then it is shaped by a cooling wheel. After rewinding, the base material layer and the adhesive layer are completely fused, and the body is formed.

Co-extrusion technology provides film multilayer structures with stronger interfacial properties. Since two or more plastic materials are extruded by high-temperature heating, the finished product will have different plastic functions. And the extruded adhesive film itself, which is completely fused with the base material layer and the adhesive layer, is integrally formed, and there will be no adhesive residue after long-term lamination, which is the biggest difference from the traditional coated protective film. Using co-extrusion extrusion technology, it is possible to adjust the appropriate plastic composition formula according to product functions or customer needs and does not require a secondary coating to process adhesive materials, to reduce costs and simplify the process.

The purpose of co-extrusion is to obtain a film with various characteristics combined into one, and the film cannot be realized by a single-layer structure, it is necessary to use co-extrusion technology to make it. The film and the adhesive layer are integrally formed, so there will be no adhesive residue in high temperatures and high humidity. The solvent-free production process is in line with green environmental protection. It has excellent characteristics of impact resistance, acid and alkali resistance, and strong surface protection. Various formulations can be prepared and easily customized.

• Physical properties.
• Mechanical properties.
• Transparency.
• Barrier properties.
• The processing performance is improved.
• Lower cost.

What are the Advantages of Using Co-extrusion Technology?

1. Physical properties / mechanical properties:
   
   • Increase hardness through polymer selection.
   • Reduced hardness to improve thermoforming properties.
   • Use high-strength raw materials to reduce film thickness without losing key properties.
   • Increased tensile strength and improved shear resistance.
   • Use multiple thin layers to improve thermal performance.
   • High-temperature resistance.
   • Low-temperature flexibility.
   • Controllable shrinkage.
   • Stress retention.
2. Surface properties:
   
   • Improve heat-sealing performance.
   • Flame resistant.
   • Anti-fog feature.
   • Oxygen getter.
   • Obtain different levels of slip and surface tension.
3. Optical characteristics:
   
   • Increase the gloss of the film with a clear outer layer.
   • Use other materials as outer layers to reduce surface haze caused by LLDPE.
   • Transparency.
   • Increase haze with less filler.
   • UV filtering and anti-fog properties.
4. Reduce costs:
   
   • No need to use secondary coating process, reduce expenses.
   • It is possible to develop composite films with various characteristics, which are easy to customize and save development time.

What are the Applications of Co-extruded Films?

• High barrier film for food packaging.
• Process protective film.
• Optical protective film.
• High transparent film for automatic packaging.
• Construction and agricultural film.
• Special medicine packaging.
• Shrink and wrap the film.
• Process-grade films for printing, lamination, and coating.

What is the Structure of Co-extrusion Products?

The reason for doing this is to produce a structure in laminated form with layers. Each layer plays an important role in improving product efficiency. Since they are coextruded, they can include more than two layers, and in some cases multiple layers. Each layer has a different function, adding to the functionality and complexity of the extruded structure.

When the composition consists of more layers, the structure is rather complex. While the primary function is to add functionality to the final product, they can help bind different layers adjacent to the initial structure, which contributes to overall compatibility.

What is the Co-extrusion Film Process?

The co-extruded film is generally divided into the casting method and the blown film method according to the current process.

Casting method:
The cast film is very transparent in appearance and soft to the touch. The thickness of the film is detected with a thickness gauge, and the thickness tolerance can reach ±2%, while the thickness tolerance of the multi-layer co-extruded film is generally within ±8%. In recent years, with the continuous improvement of technology, the thickness tolerance of film extrusion equipment with nine layers or more has been greatly improved, and the thickness of the product can be comparable to that of cast products. However, no matter what kind of film is produced, if you observe the surface of the film, you will generally find fine film lines. The film line direction of the cast film is completely parallel to the winding direction, while the film line direction of the blown film product is not parallel to the winding direction. The top is reciprocated from side to side, like a spindle, to avoid the formation of elastic edges.

Blown film method:
The common methods of blowing film are the up blowing, down blowing, two-bubble method, and three-bubble method. The blown film product is air-cooled, so the transparency is poor and the hand feel is hard. The down-blowing, two-bubble, and three-bubble products use water cooling, and the transparency of the film can be comparable to that of cast film. Among them, the two-foam method and the three-foam method produce heat-shrinkable films. The inflation ratio and the traction ratio are generally above 3. It is difficult to stretch the film by pulling the film vertically and horizontally by hand. Throw it in boiling water and the shrinkage is huge. The two-foam method generally produces POF film, which is commonly used in the packaging of barreled instant noodles. The film produced by the three-bubble method is used in the packaging of meat products.

What are the Process Characteristics of the Co-extrusion Film?

Multilayer co-extruded films are divided into the following two categories:

• High temperature and high barrier tensile structure, this series of films are mainly used for the packaging of products requiring high-temperature sterilization. For example, meat products containing bone spurs, hard air-dried meat products, and all kinds of braised egg bean products that need high-temperature sterilization.
• Low temperature and high barrier type stretch film structure: PA/TIE/PAJTIE/PEPE/MPE, this series of films are used for the packaging of pasteurized low-temperature meat products, fish, aquatic products, etc.

Resin raw materials with different functions, such as PA/PE/PP/TIE/EVOH, are melt-extruded separately, merged in a die through their respective flow channels, and then combined by inflation molding and cooling. No pollution, high barrier, strong function, low cost, small capacity ratio, high strength, flexible structure design, etc., make the production process of food packaging materials pollution-free.

Nylon resin with heat resistance, oil resistance, toughness, pinhole resistance, air tightness and transparency, and polyolefin resin with excellent moisture resistance and heat-sealing properties, are concentrated in mature technology and high-precision processing technology. As a product, the product fully displays the excellent characteristics of quality preservation, freshness preservation, taste preservation, long shelf life, oil resistance, moisture resistance, high-temperature resistance (121C), and low-temperature resistance (-50C), and extremely high strength in use. Its mechanical properties, such as oxygen and water vapor barrier properties and high-temperature cooking properties, have reached the advanced level of similar foreign products, and its transparency and flexibility are unmatched by other products.