Co-extrusion (COEX) film plastic packaging bags have become a cornerstone in the modern flexible packaging industry due to their superior performance in preserving product freshness and extending shelf life. In this article, we explore the structural composition of COEX films and reveal key techniques to enhance their barrier performance.
Layer Structure Design
The structure of COEX films typically includes multiple layers, each designed to fulfill specific functional requirements:

• Outer Layer: Provides mechanical strength and printability.

• Core Layer(s): Typically responsible for barrier performance enhancement, this layer may include materials such as EVOH or nylon for gas impermeability.

• Inner Layer: Offers sealability and compatibility with various packaging machines.

The multilayer structure allows manufacturers to optimize each layer based on desired properties, such as oxygen resistance, moisture barrier, and thermal stability.
Optimizing Oxygen Barrier Property
One of the most critical aspects of high-performance packaging is the ability to block oxygen infiltration. Materials like EVOH and PVDC are commonly used for their excellent oxygen barrier property. Key optimization strategies include:

• Layer Thickness Adjustment: Increasing the proportion of EVOH in the core layer can significantly improve the overall oxygen barrier.

• Tie Layers Application: These layers ensure adhesion between incompatible materials, such as EVOH and polyethylene.

Packaging Material Compatibility
To ensure efficient manufacturing and reliable sealing, packaging material compatibility must be carefully considered. Not all materials bond well under co-extrusion; therefore:

• Use of Compatibilizers: These additives enhance interlayer adhesion.

• Processing Temperature Control: Maintaining ideal temperatures during extrusion minimizes layer separation and defects.

Mechanical and Optical Properties
While optimizing barrier properties, it's essential not to compromise on mechanical strength and clarity. Incorporating PE or PA layers provides flexibility, puncture resistance, and transparency.
High-Barrier Flexible Packaging Applications
COEX films are widely used in:

• Food packaging: For meat, cheese, snacks, and ready meals.

• Pharmaceutical packaging: Ensuring product stability.

• Pet food and agrochemical packaging: Where high-barrier flexible packaging is essential to prevent contamination and moisture ingress.

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READ MORE:

• Balancing Performance and Sustainability in COEX Packaging Film Development

• Designing High-Barrier Flexible Packaging for Modern Supply Chains

• Engineering Compatibility in Co-extruded Packaging Films for Maximum Barrier Effectiveness