You are one of the barrier material manufactures that makes high barrier materials. Whether it’s foil lamination for pharmaceutical industry, or encapsulation barrier for OLED, your clients depend on you to provide accurate film specifications. Do you know that when writing the barrier specification, it is often limited by the sensitivity of the test method?
Take laminated foil for instance. This type of high barrier is relatively impermeable when free of defects. The tested water vapor transmission rate (WVTR) value is usually below the low-end detection limit of available instrument or method. This means you may not be accurately measure the true permeation rate due to sensitivity limits of the test method. You could end up undervalue and sell short your good barriers.
Let’s have a look at how the specification of the same foil barrier could evolve over years with the advance of technologies.
Prior to 1960, when there was no instrumental method available, WVTR was tested only with so called Cup Test, in conformance with ASTM E96. By using this test method, the WVTR specification for this foil barrier would have been written as “less than 0.5 g/(m2*day)”, which was the low detection limit of E-96 cup test.
In mid-1960’s, as infrared sensor technology became available, barrier films could be tested by instrument instead of gravimetric method. By 1990, the infrared method evolved into modulated infrared sensor technology with better precision and longer sensor life, in conformance with ASTM F1249. The same foil material was tested by using instrument, i.e. MOCON PERMATRAN-W® 3/33. The WVTR changed the specification for this barrier film from “less than 0.05 g/(m2 · day)” to “less than 0.005 g/(m2 · day)”, the low-end detection limit of F1249 method.
Today, the latest developed ultra-high barrier WVTR measurement system measures WVTR down to 0.00005 g/(m2 · day) level, allowing ultra-high barrier materials to be categorized and distinguished.
Conforming to ISO 15106-3, MOCON AQUATRAN® Model 3 uses a specially designed absolute phosphorous pent-oxide (P2O5) sensor and provides precise control of testing conditions. The same foil material is tested on this instrument, the film’s WVTR specification becomes “less than 0.00005 g/(m2 · day)”.
With the advance of technology comes more discriminating measurement, in the above case evolving over the years to become 100 times better. The specification of the exact same barrier could become 10,000 times better than it was 50 years ago - even though it is the same material. The actual barrier of the foil does not change, but each time the more sensitive test method brings the WVTR result one step closer to its true value.
Thus, the product specification is only as good
as the sensitivity of the chosen test method.
Looking back to the specifications generated by old methods, the barrier quality of your laminated foil was really undervalued.
Did you realize you may be selling your barrier short and minimizing its capability?
With new measurement technology, is it time to re-evaluate your barrier materials?
Currently, WVTR instruments are designed specifically to address each standard and are optimized for a specific analytical range. It is important to ensure you are using the appropriate WVTR measurement technique and standard for your barrier materials. By choosing the right permeation measurement equipment, you can be assured that your barriers are optimally designed, avoiding costly over- or under-packaging.
It is also important to verify your barrier properties routinely. Regular permeation QC measurements ensure your barriers continue to function properly in today’s ever-changing transportation and storage conditions.
1. ASTM International, formerly American Society for Testing and Materials, ASTM E96/E96M – 16 Standard Test Methods for Water Vapor Transmission Rate of Materials. http://www.astm.org/cgi-bin/resolver.cgi?E96E96M
2 ASTM F1249 -13 Standard Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor. https://www.astm.org/Standards/F1249.htm
3. ISO, the International Organization for Standardization, ISO 15106-3:2003 Plastics -- Film and sheeting -- Determination of water vapour transmission rate -- Part 3: Electrolytic detection sensor method. https://www.iso.org/standard/29783.html