Three-layer co-extrusion blown film is an advanced plastic film production process that involves simultaneously extruding three different plastic raw materials with varying formulations or properties through three extruders. These materials are then co-extruded within the die head and blown into a film in a single process. This technology is widely used in the production of various plastic packaging bags and films, balancing performance, cost, and stability.
1,Process Principle
Three-layer co-extrusion blown film utilizes an A/B/C three-layer structure:
Layer A (outer layer): Primarily responsible for strength, printability, and abrasion resistance.
Layer B (middle layer): Serves to enhance mechanical properties, barrier properties, or reduce costs.
Layer C (inner layer): Emphasizes heat sealing performance, flexibility, and food contact safety.
The three molten plastics are combined into a single unit within the co-extrusion die head, then blown, cooled, stretched, and wound to form a uniform film.
2,Common Material Configurations
LDPE / LLDPE: Good flexibility and heat-sealing performance
HDPE: High stiffness and strength
mPE (Metallocene Polyethylene): High strength and toughness
Recycled material (middle layer): Reduces costs and is more environmentally friendly
Can be flexibly combined according to product use, such as:
Outer layer of virgin material + middle layer of reinforced or recycled material + inner layer of food-grade virgin material
3, Main Features
Stable structure: Layers are tightly bonded and not easy to delaminate
Customizable performance: Strength, toughness, heat sealing, and barrier properties can be optimized separately
More uniform thickness: Precise film thickness control and high quality consistency
Controllable cost: Functional materials or recycled materials can be reasonably used in the middle layer
4,Technical Advantages
Balanced strength and toughness: More tear-resistant and puncture-resistant than single-layer film
Better heat-sealing performance: Secure sealing, suitable for automatic packaging
Better printing effect: The outer layer can be optimized for printing
Environmental protection and economy: Reduces raw material costs while ensuring quality
Suitable for various bag types: Flat bags, vest bags, self-sealing bags, gusseted bags, etc.
5,Typical Application Areas
Food packaging bags (frozen food, daily necessities food packaging)
Tissue and sanitary product outer packaging bags
Courier bags, mailing bags
Industrial packaging bags, liner bags
Supermarket shopping bags, garbage bags
6,Comparison with Single-Layer/Double-Layer Blown Film
Item | Single-Layer Blown Film | Double-Layer Blown Film | Three-Layer Co-extrusion Blown Film
Performance | Single | Improved | Optimal overall performance
Structure | Simple | Relatively stable | Stable and customizable
Cost | Low | Medium | High cost-effectiveness
Application Range | Limited | Wider | Widest
Three-layer co-extrusion blown film is a mature industrialized process that balances performance, cost, and stability. It is particularly suitable for the production of plastic packaging bags with high requirements for strength, sealing, appearance, and consistency, and is one of the mainstream technologies in the current plastic flexible packaging industry.
