Plastic packaging not only protects products from impact but also maintains stable quality during storage. Oxygen and moisture are two factors that directly affect product shelf life and flavor. To control them, the packaging industry relies on two important indices: OTR and WVTR. These serve as the foundation for selecting suitable materials for each application.
WHAT ARE OTR AND WVTR?
OTR stands for Oxygen Transmission Rate. It measures the rate of oxygen permeation through a plastic film under standard conditions. A lower value means higher resistance to oxidation, helping food retain color, flavor, and freshness longer.
WVTR stands for Water Vapor Transmission Rate. It is the rate at which water vapor passes through packaging. A low value indicates good moisture resistance, preventing products from absorbing water or clumping. For dry foods such as snacks, instant coffee, or powder medicine, WVTR is a critical factor.
Both indices depend on material type, film thickness, and testing conditions. Measurements are usually conducted at 23°C with humidity levels of 0% or 50%. This provides manufacturers with scientific data to choose the right materials.
TYPICAL BARRIER INDICES OF PLASTIC MATERIALS
POLYETHYLENE and POLYPROPYLENE
HDPE is known for stable moisture resistance, though its oxygen barrier is only average. LDPE is more flexible, provides decent moisture protection, but offers weak oxygen resistance. It is often combined with other layers in snack packaging. PP has low WVTR, giving better water vapor resistance than PE, making it suitable for dry foods and certain beverages.
PET và PA
PET has good oxygen barrier properties and strong mechanical strength, commonly used in carbonated drink bottles and high-quality printed packaging. PA, also known as Nylon, has strong gas barrier ability but absorbs moisture significantly, reducing effectiveness in humid environments. Therefore, PA is often laminated with PE or PP to produce vacuum-sealed bags for meat, fish, and fresh products.
EVOH, PVDC, và ALUMINUM
EVOH is considered an excellent oxygen barrier layer, frequently found in multilayer films, but it is sensitive to humidity and needs protection from PE or PP. PVDC provides outstanding resistance to both oxygen and moisture, but its high cost limits usage mainly to pharmaceuticals and premium foods. Aluminum foil is the absolute barrier, blocking oxygen and moisture entirely, and is often used in coffee, milk powder, and tablet packaging.
COMPARISON AND APPLICATION SIGNIFICANCE
No single plastic material can provide the best resistance to both oxygen and moisture. Each has specific strengths, and the choice depends on the product. Snacks require strong moisture resistance, so PE or PP is preferred. Carbonated drinks need oxygen resistance, making PET more suitable. Fresh meat and vacuum-sealed products need a combination of PA and PE.
The current trend is multilayer packaging. By combining materials such as EVOH, PET, PE, or aluminum foil, manufacturers can maximize strengths while ensuring complete protection. This approach extends shelf life while maintaining product taste and color.
VICHEM – AUTHORIZED DISTRIBUTOR OF CERTIFIED CHEMICAL ADDITIVES IN VIETNAM
Vichem is an authorized distributor of chemical additives with full legal compliance in Vietnam. We not only provide high-quality products but also deliver after-sales services that meet international standards. Our services include:
- Technical consulting: Supporting customers in selecting the right samples for intended use.
- Color testing: Vichem’s experts perform testing to ensure results meet design standards.
- Application support: Assisting customers during integration into production lines to ensure optimal performance.
For more product details, please contact us through the following channels:
📞 Hotline: 08 1790 1790
📧 Email: contact@vichem.vn
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