How Does Moisture Effect Recycled Containerboard

Zach asks:

Last week the president of one of our customers noticed a difference between a box made by our competitor and our box. The competitor’s box had a stamp saying it was made out of 100% recycled material and our box did not. He asked his quality control manager if the box made from recycled fibers might absorb moisture differently from a box made of primarily virgin fibers, and therefore fail sooner?
My knowledge tells me that all things being equal those recycled fibers will absorb moisture faster. But then it also has to vary depending upon the chemicals used at the mill, the basis weight of the paper, etc. This makes me very reluctant to make any claim that the mix of fibers in my boxes is inherently better. Are you aware of any studies that have addressed this issue?

Oh how I love this question and thank you for asking. I have attached two articles which will begin to address this issue for you.

First, there are just plain strength differences among the more than 100 machines that manufacture containerboard in the US. Recovered fibres are just more hydrophilic and take up and give off atmospheric moisture faster than new fibres and those containerboards which include more lignin.

Second, there is the whole issue of combining the components and converting the sheets. Corrugator efficiencies vary by 40% and converting crush can destroy 35% of the potential ECT strength. Where are your operation’s effectiveness verses your competitors? Did you discover the difference between semichemical medium and recycled medium through the use of Randy Bank’s DST? I am becoming a real believer in the value of shear testing.
— Ralph
Mullen until 1991, Then Edge Crush in 1991, Now Torsional Stiffness in 2013?

What ECT Does Not Tell Us About In-Place Box Performance?

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