Wisdom For Polyethylene vol.13

13. About Gas Barrier Polyethylene Bag

2025-01-21

What are multilayer plastic bags?

Multilayer bags are made solely from polyolefin resins such as PE and PP. However, this technology also allows multilayer bags to be made from resins other than polyolefins.
Therefore, they are ideal materials when there is a requirement for oxygen barrier performance or for even greater strength and pinhole resistance.

Differences from laminated bags

Laminated bags are made by laminating prepared films with a glue or adhesive resin.
There is a wide choice of materials, and the compatibility of materials is not a primary concern.

However, in the case of co-extrusion, inflation is possible using an inflation machine, and the innermost layer resin must be a heat-sealable resin (the same applies to laminated bags), and the melting points of the resins must be relatively close.
If the melting point of the barrier resin is too high, the extrusion temperature must be adjusted to match the melting point.
The innermost layer is a heat-sealable resin, i.e., polyethylene or polypropylene. If the melting points are far apart compared to polyethylene or polypropylene, carbonization occurs and production cannot take place. This is because the temperature is too high for the extruded polyethylene or polypropylene.

Summary

Item	Multilayer poly bag	Multilayer gas barrier bag	Laminated bag
Structure	Multiple resins (PE) laminated by co-extrusion	Multilayer PE bag laminated with oxygen barrier	Different films bonded with adhesive, etc.
Typical materials	LDPE, LLDPE, HDPE	Nylon, EVOH, PE	PET, metalized aluminum film, PE, etc.
Moisture resistance	Good	Good	Good
Oxygen barrier	Low to medium	High	High
Strength & durability	High	Very high	High
Flexibility	High (Adjustable: with multilayer structure)	Medium to high (depends on materials)	Medium to low (depends on materials & adhesive)
Manufacturing method	Co-extrusion	Co-extrusion with barrier resin Multilayer forming	Lamination
Material flexibility	Limited (resins with similar melting points required)	Limited (only co-extrudable materials)	High (variety of films can be combined)
Typical applications	Food packaging, pharmaceutical packaging, industrial applications	Food and pharmaceutical packaging requiring oxygen barrier	High-performance packaging, decorative packaging
Environmental consideration (recycling)	Ongoing (research on recyclable materials)	Ongoing (barrier layer is a challenge)	Difficult (recycling is hard due to mixed materials)
Cost	Medium to low	Medium to high	High

With the development of multilayer technology, the development of polyethylene bags with properties that could not be achieved with conventional single-layer films—such as moisture resistance, strength, easy opening, slip properties, and oxygen barrier performance—has progressed.

・Multilayer polyethylene bags contribute to improved flexibility, moisture resistance, and ease of opening, and are utilized in food, pharmaceutical, and industrial applications.
・Multilayer gas barrier bags prevent oxygen permeation, extending the freshness of food.
・Laminated bags, which bond different films together, offer high freedom in the choice of materials.

Furthermore, for the purpose of reducing environmental impact, the development of multilayer films using recyclable materials is progressing, with each manufacturer incorporating proprietary technologies to continue improvements.

With the ongoing advancement of multilayer technology, it is expected that more high-performance and environmentally friendly packaging materials will become available in the future.

14. The Complaints