Q3, Q4 Permeation Newsletter

 

Challenges Developing Coated Paper as a Primary Barrier

As paper-based food packaging becomes more common, coating technologies are helping paper materials meet barrier performance requirements. These barriers help preserve food throughout distribution and use by limiting oxygen and moisture transmission. Oxygen transmission rate (OTR) affects issues such as rancidity and color change, while water vapor transmission rate (WVTR) can influence texture and microbial growth.  

Testing coated paper materials presents unique challenges because paper substrates are naturally porous. Gases can migrate through exposed substrate edges during testing, a phenomenon known as edge diffusion. This can interfere with permeation measurements and reduce test accuracy. 

Results can also be influenced by temperature, humidity, material type, thickness, time and barometric pressure. Moisture-sensitive materials require especially consistent test conditions for meaningful comparisons.

To obtain reliable data, manufacturers must use appropriate testing and sample preparation methods that minimize edge diffusion. Common approaches include masking, epoxy encapsulation, mechanical edge blocking, and edge compression techniques designed to isolate coating performance and generate accurate transmission-rate measurements.

To learn more about working with coated paper board, please visit the link below.

 

Edge Compression Cartridge Helps Minimize Edge Diffusion in Paper Barrier Testing

Permeation testing of coated paper materials can be difficult because porous paper substrates allow edge diffusion, while rough or textured surfaces can make it challenging to achieve an effective seal in the test cell. These issues can affect transmission rate measurements.

To address these challenges, AMETEK MOCON developed an Edge Compression cartridge, patented in 2022, that uses cell geometry to compress the perimeter of a sample during testing. By mechanically blocking edge pathways, the method helps create a more effective seal and reduces the influence of edge diffusion on results.

The approach offers fast sample preparation and reliable sealing, making it particularly useful for coated paper structures where coating performance must be evaluated independently from the paper substrate.

Other methods, including double masking, epoxy encapsulation, and mechanical edge blocking, can also be effective depending on the material. However, edge compression provides a streamlined process while helping improve test reliability. By minimizing edge diffusion, manufacturers can generate more representative OTR and WVTR measurements for paper-based packaging applications.

 

To learn more about permeation testing with edge compression, read our application note, "Simplified Permeation Testing for Coated Paper and Textured Films":

Which Testing Solution Is Best for Your Paper-Based Barriers?

Paper-based packaging presents unique permeation testing challenges because porous substrates can allow gases to migrate through sample edges during analysis. This edge diffusion effect can influence OTR and WVTR measurements, making proper test method selection critical. 

As barrier performance improves, edge diffusion can contribute a larger percentage of the measured transmission rate. In coated paper structures, oxygen or water vapor may travel through exposed paper edges and bypass the intended test path through the coating. Effective edge control helps ensure measured results more accurately reflect coating performance rather than permeation through the paper substrate. 

Since the coating typically provides the barrier functionality, testing methods should minimize edge permeation to accurately measure coating performance. Several approaches are commonly used: 

• Double masking offers simple sample preparation and effective sealing within the diffusion cell, though rough surfaces and thicker materials may present challenges
• Single-mask epoxy encapsulation provides complete edge protection across a wide range of material thicknesses but requires additional sample preparation time.
• Edge compression mechanically seals the sample perimeter to minimize edge diffusion while supporting efficient sample preparation (see above, Section 2).
• Mechanical edge blocking uses specialized cell design and strategic seals to isolate the test area and prevent edge diffusion (see below).

Selection of the most appropriate edge-control technique depends on material construction, thickness, surface texture, and required test precision. For coated paper structures where edge diffusion can significantly influence OTR and WVTR results, dedicated edge-blocking solutions can provide more representative measurements of coating performance.

To learn more about edge compression, read our application note, "How to Achieve More Consistent Test Results Using Edge Effect Cartridges":

 

PMMI WEBINAR

Evaluating Coating Barrier Performance for Food Packaging
Presented by Michael Kragness, Permeation Application Scientist at AMETEK MOCON  

Barrier coatings are essential for protecting packaged products and achieving target shelf life, but evaluating their performance, particularly on paper-based substrates, presents significant challenges. This session will explore the fundamentals of permeation, the movement of gas or vapor molecules through a semi-permeable barrier driven by a concentration gradient. This process underpins key metrics such as oxygen transmission rate (OTR), water vapor transmission rate (WVTR), and carbon dioxide transmission rate (CO₂TR).

Click below to access the download of this webinar.

Want to learn more? Uncover a wealth of knowledge on similar topics and industries in our Resource Library.

Follow us on LinkedIn or visit our events page to be the first to know about upcoming industry events and opportunities to learn more about our solutions.