What is EVOH high barrier film?
EVOH (Ethylene-Vinyl Alcohol Copolymer) is a highly regarded high-barrier material in the field of food flexible packaging, often referred to by industry professionals as the secret weapon of premium packaging. As a polymer with excellent gas barrier properties, EVOH effectively prevents the permeation of gases such as oxygen, nitrogen, and carbon dioxide, significantly extending the shelf life of food products.
In the food packaging industry,EVOH High Barrier FilmThe core value lies in its nearly perfect ability to block oxygen. Compared to traditional PE or PP films, EVOH has an oxygen transmission rate as low as 0.1–1.0 cc·20μm/m²·day·atm, which is hundreds of times lower than that of ordinary plastic films. This means food packaging bags using EVOH as a barrier layer can provide antioxidant protection for contents for several months, making them particularly suitable for oxygen-sensitive food products.
Chemical Structure and Barrier Principle of EVOH High Barrier Film
EVOH is a copolymer of ethylene and vinyl alcohol, with its molecular structure containing both hydrophobic ethylene segments and hydrophilic vinyl alcohol segments. This unique molecular structure endows EVOH with high crystallinity and a dense molecular arrangement, making it difficult for gas molecules to pass through the intermolecular gaps—this is the fundamental reason for its excellent barrier properties.
The barrier performance of EVOH is closely related to its ethylene content. Generally, lower ethylene content (such as 32% mol) results in stronger barrier performance but greater processing difficulty; higher ethylene content (such as 44% mol) leads to slightly reduced barrier performance but improved processability and flexibility.High barrier packaging materialsThe choice often requires finding a balance between barrier performance and processability.
It is worth noting that EVOH is a hydrophilic material, and its barrier properties may decrease in high humidity environments. Therefore, in practical applications, the EVOH layer is typically sandwiched between hydrophobic materials such as PE and PP, forming a multi-layer composite structure. This approach utilizes EVOH’s excellent barrier properties while protecting it from direct exposure to moisture through an outer layer.
Main application scenarios of EVOH in food packaging
1. Meat and Seafood Packaging
Fresh meat, ready-to-eat foods, cured meats, and seafood products are highly sensitive to oxygen. Exposure to oxygen can cause fat oxidation, color changes, and microbial growth. Vacuum packaging bags or modified atmosphere packaging with an EVOH barrier layer can extend shelf life from a few days to several weeks or even months. For example, premium ham slices packaged with an EVOH layer can maintain freshness for over 45 days under refrigeration conditions.
2. Coffee and Tea Packaging
Coffee beans and ground coffee are highly sensitive to oxygen. Once exposed to oxygen, oxidation occurs, leading to the loss of aroma and deterioration of flavor. With an EVOH layer,Coffee BagCombined with a one-way exhaust valve, it prevents external oxygen from entering while allowing internal carbon dioxide to escape, making it an ideal solution for premium coffee packaging.
3. Sauce and Seasoning Packaging
Oily sauces, seasonings, and concentrated soup pouches also face oxidation issues. EVOH high barrier film can effectively prevent oil oxidation and rancidity, while preserving the original flavor of the seasonings. ManyComposite Packaging MaterialsThe three-layer structure of PE/EVOH/PE balances heat-sealing performance with barrier requirements.
4. Infant Food and Nutritional Products Packaging
Infant formula milk powder, nutritional rice cereal, and other products have extremely high requirements for packaging safety and freshness preservation. EVOH material itself meets food contact material safety standards, and when combined with aluminum foil or metallized layers, it provides comprehensive protection for these high-value products.
Comparison Analysis of EVOH with Other High Barrier Materials
| Material | Oxygen Transmission Rate | Humidity Influence | Cost | Applicable Scenarios |
|---|---|---|---|---|
| EVOH | Very low (0.1-1.0) | Affected by humidity | Mid to High | Food and Pharmaceutical Packaging |
| PVDC | Low (0.5-5.0) | Less affected by humidity | Chinese | Meat and Cheese Packaging |
| PA (Nylon) | Mid (10-50) | Relatively stable | Chinese | High-temperature steam sterilization packaging |
| Aluminum Foil | Almost Zero | Not affected | Chinese | Products requiring complete light protection |
As shown in the table, EVOH performs best in applications involving dry food and moderate humidity, making it an ideal choice for packaging projects that require high transparency and excellent barrier properties.
Structural Design and Process Key Points of EVOH Packaging
Typical EVOH composite film structures usually employ a symmetrical design, such as PE/adhesive layer/EVOH/adhesive layer/PE. Adhesive layers are necessary because EVOH has poor affinity with polyolefin materials such as PE and PP, and direct lamination can lead to delamination. The adhesive layer, typically a modified polyolefin, acts as a bridge to ensure strong bonding between the layers.
In terms of process, EVOH composite films can be produced using dry lamination, extrusion lamination, or solventless lamination. Among these, solventless lamination is becoming the preferred choice for more packaging factories due to its environmental benefits. Regardless of the process used,Custom Soft PackagingPrecise control of temperature, tension, and adhesive amount during the process is essential to ensure the barrier performance of the EVOH layer is not compromised during processing.
How to Choose the Right EVOH High Barrier Packaging Solution
When selecting an EVOH high barrier packaging solution, enterprises need to consider the following factors comprehensively:
- Product Features:Water activity, fat content, and shelf life requirements for food
- Storage Conditions:Normal temperature, refrigerated or frozen storage conditions
- Packaging Form:Vacuum packaging, modified atmosphere packaging, or regular sealed packaging
- Cost Budget:The addition of EVOH will result in some increased costs, which needs to be balanced against the benefits of extended shelf life.
- Environmental Requirements:Some EVOH composite films can be designed as single-material structures, facilitating recycling.
For companies new to EVOH packaging, it is recommended to start with a small-scale trial production, validate the packaging solution through accelerated aging tests, and then proceed to full-scale production.
If you are looking for EVOH high barrier packaging solutions, welcomeContact Huashu PackagingOur professional technical team will provide a complete packaging customization service, from material selection to process optimization, based on your product characteristics.