When producing plastic packaging bags, "middle layer", "inner layer", and "outer layer" refer to different layers in the bag structure. Plastic packaging bags with multi-layer structures can provide better performance and characteristics to meet different usage requirements.
1,Outer layer
Function: Printing performance: The outer layer is usually used for printing, and can print brand logos, instructions for use, barcodes, etc.
Protection: The outer layer protects the bag from external environmental influences such as moisture, light, and mechanical damage.
Aesthetics: Provides a smooth and beautiful surface to enhance the visual appeal of the packaging bag.
Common materials: Polyester (PET): has good printing performance and wear resistance.
Polypropylene (PP): Durable and has good transparency.
2,Middle layer
Function: Barrier performance: The middle layer mainly provides barrier properties to prevent the penetration of oxygen, moisture, odor, etc., and extend the shelf life of the contents.
Strength: Enhance the overall strength and toughness of the packaging bag to prevent tearing and puncture.
Common materials: Nylon (PA): has excellent barrier properties and mechanical strength.
Ethylene-vinyl alcohol copolymer (EVOH): has extremely high gas barrier properties.
3,Inner layer
Function: Sealing performance: The inner layer is in direct contact with the contents and must have good sealing performance to ensure the safety and leakage prevention of the contents.
Food safety: For food packaging, the inner layer needs to meet the safety standards of food contact materials and cannot contaminate food.
Common materials: Polyethylene (PE): has good sealing and flexibility and is the most commonly used inner layer material. Linear low-density polyethylene (LLDPE): Enhanced sealing and durability.
Advantages of multi-layer structure
Comprehensive performance: Through the combination of different materials, plastic packaging bags can combine the advantages of each layer of materials, such as high strength, excellent barrier properties and good printability.
Cost-effectiveness: The use of multi-layer structure can optimize the use of materials and reduce costs while maintaining performance.
Special uses: The multi-layer structure can be adjusted according to different needs, such as special functions such as anti-static and UV protection.
Practical application examples
Food packaging bags:
Outer layer: PET, providing good printing performance and wear resistance.
Middle layer: EVOH, providing high barrier properties to prevent oxygen and moisture penetration.
Inner layer: LLDPE, ensuring food contact safety and good sealing.
Express packaging bags
Outer layer: PP, providing good wear resistance and waterproofness.
Middle layer: PA, enhancing strength and tear resistance.
Inner layer: PE, ensuring that the contents are not affected by the outside world and have good sealing.
By using a multi-layer structure, plastic packaging bags can meet the needs of different application scenarios and provide excellent performance and reliability.
