Moisture and gas barrier: when is it really necessary

The question about moisture and gas barriers often comes from two opposing directions: one side worries that the packaging does not adequately protect the product, while the other side is concerned about paying for features they do not need. Both concerns are valid. Sinh Vũ starts not from materials but from a simpler question: what causes your product to fail?

Two different problems.

Oxygen barrier and moisture barrier are two distinct functions. A material strong in one aspect may not be strong in the other, which is why modern packaging films often combine multiple layers to address both.

• Gas barrier (primarily oxygen): necessary when oxygen is the culprit, meaning products are prone to spoilage, discoloration, or loss of aroma, such as roasted coffee, oily seeds, ready-to-eat snacks, or pharmaceuticals.
• Moisture barrier: necessary when moisture is the culprit, meaning products absorb moisture, losing crispness or clumping, such as snacks, flour, seasoning powders, or salt.
• Need both: many products are sensitive to oxygen and moisture, especially when they have a long shelf life or pass through various climates in the export chain.

The two technical indicators you will encounter when working with the printer are OTR (oxygen transmission rate) and WVTR (water vapor transmission rate). Both are measured in units transmitted through the membrane over a period of time: the lower the number, the better the membrane blocks.

When to choose which level

Note: OTR figures classify high, medium, and low levels in technical documents always come with specific measurement conditions regarding temperature and relative humidity. Sinh Vũ does not commit to a specific OTR or WVTR for the print batch; that responsibility lies with the printer to confirm based on actual materials. Sinh Vũ's role is to finalize the functional requirements so that the brief for printing does not need to be redone.

The subtle point about EVOH and moisture

EVOH (ethylene vinyl alcohol) is a very strong oxygen barrier material, commonly found in multilayer film structures for oxygen-sensitive foods. However, one important point to note is that EVOH is sensitive to moisture. When exposed to moisture, its oxygen barrier capability significantly decreases. Therefore, in structures using EVOH, a moisture barrier layer must be included to protect both sides of the EVOH layer.

This is a typical example of the layering principle: it’s not about choosing a single material that does everything well, but rather layering materials so that each layer performs its specific function.

A material that is strong in blocking air may not be strong in blocking moisture. Layering is the only way to address both issues simultaneously.

Teinnovations, Barrier Packaging Tradeoffs

Common errors

• Invest in high barriers for products that don't need them: inflating packaging costs, unable to recoup value because the product sells before the barriers take effect.
• Remove barriers to save costs: Products decline quickly, customer complaints arise, leading to returns or loss of reputation, making actual costs higher than the initial savings.
• Confusing moisture barriers with gas barriers: Choosing the wrong strong film, for example, selecting a moisture barrier that is good for products damaged by oxygen, results in continued damage.
• Only focus on the main material, ignoring the layered structure: especially when using EVOH without a protective moisture barrier, the actual effectiveness is lower than theoretical.

Sinh Vũ's viewpoint

Sinh Vũ begins with the question of degradation mechanisms: does the product degrade due to oxygen, moisture, light, or a combination of these factors? Then, two additional questions are asked: what is the target shelf life, and what environments does the product pass through from storage to the consumer's hands? Only when both pieces of information are available can the actual barrier level be determined.

From there, Sinh Vũ works with partner printers to finalize the membrane structure that meets the requirements. Sinh Vũ does not provide technical certification, nor does it commit to specific OTR or WVTR numbers for a print run. That responsibility lies with the material supplier and the printer. Sinh Vũ's role is to translate product protection requirements into a clear technical brief to avoid backtracking in the process.