Archive for the ‘Containerboard’ Category

What is the difference between ECT and ECV?

June 9, 2017

Charles asks,

What is the difference between ECT and ECV?

ECT (Edge Crush Test) is the testing method. ECV (Edge Crush Value) is the actual outcome or reported result of the Edge Crush Test. ECT is a measured in pounds per lineal inch of load bearing edge. Though it may sometimes be reported as ECV or lb/in it is typically reported or listed as an ECT value such as 23 ECT.

ETC has widely replaced the use of the Mullen test as ECT is considered by most as a more accurate test of the stacking strength of a corrugated box. It measures the edgewise compressive strength of a corrugated sample on an axis parallel to the sheet. Mullen, on the other hand, measures the bursting strength of the face of the corrugated sample, or on an axis perpendicular to the sheet.

– Ralph


Moisture Test Comparison MRA vs. non-MRA Box

May 24, 2017

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

White Linerboard Cracking at Score

March 24, 2017

Dana asks,

Regarding cracking on white liners, is there one specific liner type that will fare better than another?  Considering Kemi, Bleached White and Mottled White liners which is likely to provide the best performance and quality for rotary die-cutting with a perforation pattern of 3/8″ x 3/8″ perf-score or 1/2″ x 1/2″ perf-score.

In my experience, we have compared Mullen grades to ECT grades and understand the longer fibers to fare better than shorter fibers, but I have never before been asked this question in regards to the specific liner board color. I am curious to know if you have any data or experience related to this.

Kemi is extremely uniform and well-formed of virgin Northern European short hardwood fibres. Bleached white from the US South will be different than Canadian bleached. There is no more mottled white.  White tops can be composed of virgin or recycled fibres or a combination of both.  These are also made in the US South and Canada.

I would invest in a small microscope that you can connect to a laptop and look at the cross sections of both good and bad scores to see what is happening to the medium in both situations.  You might also consider sending samples back to your sheet feeder for flat crush testing. You may need a different medium.

Do you have the right rule and rubbering for the dies?  What does the supplier say?  If they do not know I will recommend an expert to you. Also, are your dies in good condition with no damaged rule or rubber? And don’t forget your anvil covers/blankets. Are they in good condition and do they have an even surface? It’s important that they are rotated, ground or trimmed frequently to maintain the proper anvil surface.

Cracking during the winter is often a matter of low moisture.  What combined board moisture do you have at the time of converting.  Do you know the individual containerboard temperatures at the time of combining on the corrugator?  It’s possible your supplier is ‘cooking’ the sheet on the corrugator causing it to become more brittle than desired.  Consider a Denver Moisture Analyzer somewhere in your system?  You need at least 7% moisture to have any success at scoring properly.

How is the maintenance on your presses?  Do you experience cracking more on one diecutter than another? Are there differentials between shifts?

Let me know how your investigation proceeds. I would be very interested in what you discover.

— Ralph

German to US Board Equivalents

March 22, 2017

Luke asks,

Quite often, I receive requests to spec out a box that was originally designed in Europe– most often Germany or Belgium. I have had a really hard time finding US equivalents to some of the board combinations used “over there”, both in flute and paper weights. What we struggle with most is the board codes (e.g. PLK 140/ WS 115/ TL 140 or TLW135/WS70/TL135, ZNNW43).

Is there a resource out there somewhere that I can utilize to best determine a US analog for flute combo/paper weights?

To answer your question about your specific combination above it would be coated liner 29#/ waste based 23#/Testliner 29# and test liner white 28#/waste based 14#/test liner 28#. I have no idea of the ZNNW 43 name. However, take a look at these two documents. They may give you the information you need. Alternative Requirements Table, Transport Quality Requirements.