OTR, WVTR, Heat Seal Strength — How To Read An Aluminum Foil Composite Film Spec Sheet?

OTR, WVTR, Heat Seal Strength — How to Read an Aluminum Foil Composite Film Spec Sheet?

The Most Common Confusion in Procurement: So Many Parameters, Which One Matters Most?

When you receive a quotation for aluminum foil composite film, the attached spec sheet usually lists a dozen parameters: thickness, tensile strength, OTR, WVTR, heat seal strength, surface tension, coefficient of friction... For procurement managers without a materials science background, these abbreviations and numbers feel like a secret code.

The truth is: there is no single "most important" parameter — only the most suitable combination.

The core need of food packaging is freshness preservation, and the essence of freshness is controlling mass exchange — blocking external oxygen, moisture, and light from entering, while preventing internal aroma and oil from migrating out. The three-layer structure of aluminum foil composite film (PET/AL/PE) is designed precisely for this purpose. Understanding the parameters means understanding what kind of "protective shield" your food needs.

OTR : Why Does Coffee Packaging Require ≤1, While Regular Snacks Can Tolerate More?

(OTR (Oxygen Transmission Rate), measured in cm³/m²·24h·atm, represents the volume of oxygen passing through one square meter of film in 24 hours under standard temperature and humidity conditions.)

Aluminum foil composite film typically achieves OTR ≤ 0.5, thanks to the "absolute barrier" of the 6–9μm aluminum layer — theoretically near-zero OTR, with actual values mainly coming from microscopic pinholes and edge permeation in the laminate.

(Procurement Tip: If a supplier quotes OTR "≤ 1.0", it may be insufficient for coffee products; but for short-shelf-life baked goods, the difference between 0.5 and 1.0 may not justify a 20% price premium.)

WVTR : Different Considerations for Humid vs. Dry

(WVTR (Water Vapor Transmission Rate), measured in g/m²·24h, measures the film's ability to block water vapor penetration.)

Aluminum foil composite film typically achieves WVTR ≤ 1.0, with the aluminum layer playing the dominant role. However, note that PE layer thickness directly affects WVTR — PE is the main pathway for moisture transmission, and increasing PE thickness (e.g., from 60μm to 100μm) can significantly reduce WVTR.

Heat Seal Strength vs. Temperature: How Production Line Speed Affects Parameter Selection

(Heat Seal Strength, measured in N/15mm, represents the maximum tensile force the seal can withstand.)

Key Insight: Higher heat seal strength is not always better. Excessive strength requires higher temperature or longer dwell time, which leads to:

● Over-melting of the PE layer, causing thinning or pinholes

● Reduced production speed and lower throughput

● Increased energy consumption and higher costs

Conclusion: Parameters Are Tools; Needs Are the Starting Point

A spec sheet for aluminum foil composite film is not about being the most impressive — it's about being the most relevant. As a procurement decision-maker, your job is not to memorize all abbreviations, but to clearly answer three questions:

What does my food fear most? (Oxygen, water, light, oil, microbes)

What is my target shelf life? (3 months vs. 24 months make vastly different parameter demands)

What is my production line capability? (The best parameters are worthless if your line cannot achieve them)

Bring these three questions to your supplier conversations, and you'll find that professional suppliers will ask you these questions proactively — instead of just handing you a standard spec sheet.