Understanding High Barrier Properties in Food-Grade Plastics

As the food packaging industry evolves, there is an increasing demand for materials that not only preserve the quality of food but also extend its shelf life. High barrier properties play a crucial role in achieving this, as they help prevent the permeation of gases, moisture, and aromas that can compromise food quality. Among the various materials used in food packaging, ethylene vinyl alcohol (EVOH) and polyvinyl alcohol (PVOH) stand out for their high barrier properties. This article explores these two materials, comparing their benefits and uses in food-grade applications.

What are High Barrier Properties?

Before diving into the specifics of EVOH and PVOH, it is essential to understand what high barrier properties mean. In the context of food packaging, barrier properties refer to a material's ability to resist the passage of substances such as oxygen, carbon dioxide, and water vapor. High barrier properties are crucial for maintaining the freshness, flavor, and nutritional value of food products while extending their shelf life.

Ethylene Vinyl Alcohol (EVOH)

EVOH is a copolymer of ethylene and vinyl alcohol, recognized for its superior barrier properties against gases. It is often used as a barrier layer in multi-layer packaging structures. EVOH's effectiveness stems from its crystalline structure, which creates a dense network that inhibits the passage of gases. This material is particularly valued for its ability to preserve the aroma and taste of food products.

Advantages of EVOH in Food Packaging

1. Excellent Gas Barrier: EVOH is known for providing outstanding protection against oxygen and other gases, making it ideal for packaging oxygen-sensitive products like coffee, fresh meats, and dairy.

2. Versatility: EVOH can be co-extruded or laminated with other polymers, allowing manufacturers to tailor packaging to meet specific needs without compromising barrier performance.

3. Recyclability: Although EVOH itself is not easily recycled, its incorporation in multi-layer structures can be managed in recycling processes, especially when combined with compatible materials.

Polyvinyl Alcohol (PVOH)

PVOH is a synthetic polymer known for its excellent film-forming and adhesive properties. While not as prevalent as EVOH in food packaging, PVOH offers unique benefits in specific applications. Its high barrier properties are particularly effective in preventing the transmission of oxygen and odors.

Key Benefits of PVOH

1. Exceptional Oxygen Barrier: PVOH is particularly efficient at blocking oxygen, making it suitable for applications where oxidation is a significant concern.

2. Water Solubility: Unlike EVOH, PVOH is water-soluble, which can be advantageous or disadvantageous depending on the application. This property is beneficial for creating water-soluble pouches and films.

3. Biodegradability: PVOH’s water solubility contributes to its biodegradability, offering an environmentally friendly option for certain packaging applications.

Comparing EVOH and PVOH

While both EVOH and PVOH offer high barrier properties, their differences make them suitable for distinct applications in food-grade packaging.

1. Application Specificity: EVOH is more commonly used in traditional packaging due to its versatility and ease of processing with other polymers. PVOH, on the other hand, is selected for niche applications where water solubility is required.

2. Moisture Sensitivity: EVOH maintains its barrier properties better in humid conditions compared to PVOH, which can lose effectiveness as it absorbs moisture.

3. Environmental Impact: PVOH’s biodegradability may provide an edge in applications seeking sustainable solutions, while EVOH’s adaptability in recycling processes makes it a viable option for broader usage.

Conclusion

In the world of food-grade plastics, both EVOH and PVOH offer significant advantages due to their high barrier properties. The choice between these materials largely depends on the specific needs of the application, such as the type of food being packaged, environmental considerations, and desired shelf life. As packaging technologies continue to advance, the role of high barrier materials like EVOH and PVOH will remain critical in ensuring food safety and quality while meeting the ever-evolving demands of consumers and regulators.