Understand the Multi-Layer Co-Extrusion Structure of Thin Films in One Article: Why Has It Become the “Standard” for High-End Packaging?

Preface 

Vacuum-packed meat packaging for supermarkets, inner-layer film for high-temperature sterilized milk cartons, and high-barrier composite films for snacks. …… These everyday films are mostly made using “ Multi-layer co-extrusion ” Structure—within a single thin film, there may lie... 3-7 The mystery of layers made of different materials. 

Multi-layer co-extrusion technology is key to upgrading film performance, breaking the performance limitations of single-layer films. By precisely combining materials and employing integrated molding, it achieves multifunctional integration—including barrier properties, freshness preservation, temperature resistance, and easy heat sealing. This article dissects the core logic of multi-layer co-extrusion structures from the perspectives of principle, advantages, and applications. 

I. Basic Understanding: What is a multi-layer co-extruded film? 

Multilayer co-extruded film is a product formed by combining molten plastics of two or more different materials through multiple extruders within the same die. Its core characteristic is: “ Multi-layer integrated ” The molten layers are tightly bonded with no obvious interface, and their performance is superior to that of conventional dry-laminated films. 

(1) Core Principle: Multi-machine collaboration, one-step forming. 

The multi-layer co-extrusion production process can be summarized as: “ Multi-machine collaboration, one-step molding. ”：

Multiple extruders are heated and melted separately. PE 、 PP and different materials; 

The molten material is precisely layered according to a preset number of layers and thickness ratios using a co-extrusion die. 

The composite melt is cooled and shaped by blow molding or cast film processes to form a multi-layer co-extruded film. 

Compared to traditional dry lamination, multi-layer co-extrusion eliminates the need for adhesives, simplifying the process while also avoiding potential residual hazards, making it particularly well-suited for high-end packaging applications in industries such as food and pharmaceuticals. 

(2) Floor Division: 2-7 Layer-based, custom-made on demand 

There is no absolute upper limit to the number of layers in multilayer co-extruded films; commonly used in industry. 2-7 Layer, can reach special scenarios 9 Above the layer, the number of layers is determined by application requirements: 

• 2-3 Layer : Basic style, such as “PE/PP” “PE/EVOH” Meets the barrier and heat-sealing requirements for standard packaging, suitable for supermarket shopping bags and simple food packaging. 
• 4-5 Layer : Mid-to-high-end models, such as “PP/PE/EVOH/PE/PP” , add reinforcement / Functional layer that enhances temperature resistance and puncture resistance, suitable for high-temperature sterilized foods and vacuum-packed preserved products. 
• 6-7 Layer and above High-end custom-made product with optional antibacterial, light-shielding, and easy-tear layers, suitable for pharmaceuticals, infant food, and electronic component packaging. 

II. Core Advantage: Why Can Multi-layer Co-extrusion Replace Single-layer Films? 

Single-layer membranes are easily limited by materials. “ To lose sight of one thing while focusing on another. ” , such as PE The membrane has good toughness but poor barrier properties. PET The film has good barrier properties but is difficult to heat seal. Multi-layer co-extrusion can help. “ Complementary advantages ” Addressing this pain point has become the core reason for its widespread adoption. 

(1) Diversified performance, adaptable to multiple scenario requirements. 

The combination of different materials endows multilayer co-extruded films with diverse performance characteristics, making them suitable for a wide range of applications. 

• High barrier property : Join EVOH 、 PVDC or an aluminum foil layer that reduces the permeability of oxygen, carbon dioxide, and water vapor, thereby extending shelf life. Contains EVOH The oxygen permeability of the thin film layer can be lower than 1 cc/(m²·24 h·atm) It's a single layer. PE of the membrane 1/100 Above; 
• Excellent heat sealability : Inner layer uses PE 、 PP Easy-to-heat-seal materials that enable rapid sealing, offer high heat-sealing strength, and are resistant to leakage of liquids and gases. 
• Temperature and weather resistance : Outer layer uses PET 、 PA High-temperature-resistant materials that can withstand 121℃ High-temperature sterilization, suitable for canned goods and high-temperature milk packaging; 
• Customized special features Add antibacterial, antistatic, and light-shielding agents to achieve specialized functions, suitable for the pharmaceutical and electronics industries. 

(2) Costs are more controllable, and the cost-performance advantage is obvious. 

Multi-layer co-extrusion through “ Precise ingredient usage ” While ensuring performance, also control costs: 

High-priced functional materials (such as EVOH ) serves as an intermediate layer, with a thickness of only 10–20 μm The outer and inner layers use cost-effective materials. PE 、 PP Reduce the use of high-cost materials; 

The one-step molding process eliminates steps such as adhesive application and drying, thereby boosting production efficiency. 30% Above, unit costs have been reduced. 15-25% 。

(3) More safe and environmentally friendly, aligning with industry development trends. 

Under tightening environmental policies and heightened safety awareness, the environmental advantages of multi-layer co-extrusion are becoming increasingly prominent. 

No adhesive residue: Avoid. VOC Residue complies with food contact safety standards; 

High recyclability: Multi-layer films made from the same series of materials (such as all-polyolefins) can be recycled using a single material, thereby addressing the challenges associated with separating traditional composite films. 

Compatible with biodegradable materials: With PLA 、 PBAT Compatible with existing systems, we produce biodegradable multilayer films to support the advancement of environmental protection. 

III. Key Technology: Multi-layer Co-extrusion Structure “ Password pairing ”

The core of multi-layer co-extrusion lies in material selection; different application scenarios call for tailored structural combinations. Below are some common industry solutions: 

(1) Food Packaging Sector: Prioritize Ensuring Barrier Properties and Safety 

Food packaging has high requirements for barrier properties, temperature resistance, and heat-sealing performance. Common structures and applications: 

• General food packaging (snack bags, bread bags) ：3 Layer “PP/PE” , outer layer PP Ensures crispness and printability, inner layer PE Responsible for heat sealing; a calcium carbonate layer can be added to the intermediate layer to enhance light-blocking performance. 
• Vacuum packaging for fresh meat and cooked foods ：4 Layer PA/PE/EVOH/PE ， PA Enhance puncture resistance, EVOH Enhance barrier properties, PE Ensure heat sealing and flexibility; 
• High-temperature sterilized food packaging (high-temperature milk, canned goods) ：3 Layer “PET/PA/PP” ， PET With PA Enhance temperature resistance (can withstand) 121℃ Sterilization), PP Serve as a heat-sealing layer. 

(2) Pharmaceutical Packaging Sector: Focus on ensuring sealing performance and cleanliness. 

Pharmaceutical packaging has stringent requirements for sealing, barrier properties, and cleanliness. Common structures include: 

• Pharmaceutical packaging film (tablets, capsules) ：3 Layer “PET/AL/PE” ， PET Responsible for print protection; aluminum foil achieves high barrier properties. PE Ensure heat sealing; 
• Medical device packaging film (syringes, surgical instruments) ：3 Layer “PET/EVOH/PP” ， EVOH Ensure barrier properties, PP It is ethylene oxide sterilizable and does not release any harmful substances. 

(3) Industrial Packaging Sector: Focus on Ensuring Strength and Weather Resistance 

Industrial packaging (for electronic components and building materials) focuses on strength and weather resistance; common structures include: 

• Electronic component packaging ：3 Layer “PET/PA/PE” Add an antistatic agent to prevent static electricity from damaging components. 
• Building material packaging (profiles, boards) ：3 Layer “PP/PE/PP” , outer layer PP Improve weather resistance, intermediate PE Enhance resilience and protect building material surfaces from scratches. 

IV. Industry Challenges and Development Trends 

Multilayer co-extrusion technology boasts significant advantages, yet the industry still faces challenges. At the same time, as technology advances and demand evolves, clear development directions are emerging. 

(1) The Core Challenges Currently Faced 

• High equipment threshold The production line requires multiple high-precision extruders, specialized co-extrusion die heads, and a precise control system; the investment is higher than that of a single-layer line. 3-5 Moreover, small and medium-sized enterprises find it difficult to afford; 
• Difficult process control Different materials have significantly varying melting temperatures and flow characteristics. Achieving uniform multilayer compounding and stable molding requires extremely precise parameter control and must be performed by skilled professionals. 
• High-end materials rely on imports. High-end EVOH Special modification PA High-performance materials still rely on imports, and the stability and cost-effectiveness of domestically produced materials remain to be improved. 

(2) Future Development Trends 

• Environmental upgrade Degradable multilayer films are a key R&D focus, while simultaneously accelerating the development of the entire... PE , all PP Develop multi-layer films made of a single material to enhance recycling efficiency; 
• Intelligent manufacturing Introduce IoT and big data to enable real-time monitoring and intelligent control, coupled with online inspection equipment, to enhance quality stability and reduce defect rates. 
• Function precision : The number of customized structures tailored to specific scenarios is increasing, such as... “ Antibacterial + High barrier ” Combination to meet the precise needs of the industry; 
• Localization substitution accelerates. Domestic enterprises are stepping up R&D efforts in high-end materials and core equipment. EVOH The localization rate of key components such as co-extrusion die heads has increased, lowering the industry’s entry barriers. 

Conclusion 

Multi-layer co-extrusion structures represent a shift in the film industry from... “ Single performance ” towards “ Multifunctional integration ” An important indicator of upgrading is breaking through performance limitations via innovative material combinations and process technologies, thereby meeting the high-end demands of sectors such as food, pharmaceuticals, and industry. This represents the core direction for high-quality development in the industry. 

For membrane manufacturers, mastering this technology means enhancing their competitiveness in the high-end market. For downstream enterprises and consumers, multilayer co-extruded films offer safer, more environmentally friendly, and more practical packaging solutions. As environmental policies become stricter and technology continues to advance, the application scenarios for these films will further expand, promising a bright future ahead. 

What technical challenges have you encountered when using or procuring multilayer co-extruded films? What are your expectations for their future development? Feel free to share your thoughts in the comments!