Moisture Test Comparison MRA vs. non-MRA Box

Steve asks,

Would you have or could you please direct me towards any testing data/statistics on a box with MRA vs. a non-MRA box?  I would like to see what kind of improvement it shows in a moisture-related test.

The dimensions, flutes and composition range (very small to large boxes; B/C, E/B, and B flutes; 32ECT to 71ECT), and I don’t have much info on supply chain.  A customer just looking for any testing data that he can get on MRA to demonstrate that it does improve performance in moisture.

For assistance with answering this question I reached out to Clayton Clancy at Kruger. He has provided this this detailed study on stacking performance when using water-resistant adhesives, complied by the Institute of Paper Chemistry, which high-lights paperboard performance improvements when using WRA additives. He cautions that there are varying terminologies used when discussing water resistance such as (MRA, WRA and WPA), with that in mind I hope this will be helpful.

— Ralph

One Response to “Moisture Test Comparison MRA vs. non-MRA Box”

  1. Brett Kendall (@pourlefun) Says:

    A simple test to tell the difference is simply to soak sample (flutes vertical) for 24 hours in 72 degree water. Untreated starch adhesive comes apart in 20 minutes but MRA should not come apart (liner off the flute tips) by more than 0.25″ after 24 hours. With WRA or WPA levels of resin, there should be some tack remaining at the starch bond as you pull it apart.

    Let’s not forget that MRA/WRA/WPA are labels we give to the performance of the starch bond, generally indicated by the amount of wet-strength resin in the starch adhesive. These resins do not directly contribute to box strength, they simply allow the starch to keep doing its job when in high humidity. Many times I’ve heard people blame soft/collapsing boxes on the the lack of resin in the starch. If the liners and medium are stuck together, soft boxes can’t be blamed on a resin that gets no penetration into the paper.


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