Archive for the ‘Paper’ Category

Corrugated Shelf Life, Storage and Usage Temps, Toxicity?

April 9, 2019

Chris asks:

Do you have any resources for the following information regarding corrugated containers?

As the answers would appear to be specific to the material composition, these would be for plain C-Flute kraft containers.

  • Shelf Life
  • Service Temp Range
  • Storage Temp
  • Toxicity

These questions are asked quite often on Ask-Ralph. This may not be a complete answer to your question, but it is a start to the dialogue.

Corrugated under compression (loaded and stacked) ages/deteriorates at a different rate than KD boxes on a pallet. Environment, fill load, stacked load, potential crush during converting all contribute to the deterioration rate of a loaded box.

Ideally, whether loaded or stored as knock downs, corrugated should be stored at 72 degrees and 50% RH.  That’s a perfect world and few of us live in a perfect world. Any fluctuations in these conditions can reduce the fibre to fibre bonding and strength of the adhesive bond. Temperature does effect stored corrugated, but it’s the combination of temperature and humidity that has the greatest effect. High temps (90 plus degrees F) and low humidity and you’re likely to start to see score cracking and brittle paper issues. High temps and high humidity and you’re likely to start seeing bond breakdown and an increase of the compressive creep rate leading to increased chances of failure under load.

At extreme low temps and you may start to experience recharacterizations of adhesive that can lead to failures at joints and even at the liner to medium bonds. Same holds true here with humidity though it may not be as severe as with high temps.

General rule of thumb, if it is comfortable to work in, it’s probably good for corrugated. We don’t like to be hot and sweaty or numb from cold… neither does corrugated.

As far as toxicity, corrugated is considered an indirect food additive by the FDA and is detailed in 49 CFR.  Therefore, no toxicity for plain kraft. If there are inks or coatings involved, then you have to look that them on an individual basis.

Now there’s a start to the discussion. What input do our readers have?

— Ralph

Checking Moisture of Corrugated Sheets

January 31, 2018

Tim asks,

Recently we encountered corrugated sheets with dry liners and medium that created problems converting. Is there a way for us to test sheets for moisture content at our facility? If so, is there a listing of the ranges?

Moisture meters, or moisture analyzers, can be used to test the moisture content of corrugate sheets. There are a number of portable, hand-held models available. (Most look surprisingly like a taser) They are rather inexpensive (ranging from $50 to $600) and a modest range of testers with varying capabilities and features are available in this range. These units provide instant readings of paper moisture content and should meet your needs. If you purchase a meter/analyzer make sure it is suitable for measuring paper. Some of the least expensive models are only for wood or hard materials. Also check the accuracy rating of the device. If it has a .01% or .02% for paper it should do fine. The same devices may have a 1% – 3% accuracy for wood, but that won’t affect testing paper.

6 to 8 percent moisture is the sweet spot for corrugated paperboard. Below 6% and the risk of cracking scores will increase, perhaps significantly depending on the paper. If the moisture content goes above 8% you will start to see a decrease in compression strength. Reports indicate compression strength can decrease as much as 6.5% per every 1% of moisture over 8%.

Now, in your case (simple checking for machineability) moisture meters/analyzers should work fine. However, they are not the most accurate method for checking paperboard moisture. Should you ever need to certify board for food or pharmaceuticals you may want to find a testing facility that can provide results via the oven method.

– Ralph

Decoding Customer’s Specs

January 3, 2018

Richard asks,

I was a given a spec for an RSC with the paper spec’d as:

K7K 230g + 140g + 230g Kraft C/F.

I don’t know how to interpret this. I’ve reached out to our board suppliers, but I thought you may be able to shed some light. I’m assuming this is a standard way to spec board in some other part of the world.

The paperweight is the easiest to decode. To convert the paper weights from grams to #/MSF simply divide the values by 4.88 and round accordingly to match the closest available weight.

Therefore,

  • 230g = 47.13
  • 140g = 28.68

The other parts of the specification may be a code that is specific to the customers operation. The K7K probably denotes Kraft over Kraft liners and not test liner. The 7 is the caliper, 7mm or .177”. The ‘Kraft C/F’ probably denotes Kraft Corrugated Fluting.

However, that’s a lot of ‘probablies’. To be on the safe side I would try to get the customer to confirm the K7K and the C/F.

– Ralph

Dual Arch Medium

December 1, 2017

Bruce asks,

I am searching for a company that manufactures corrugated sheets with dual arch medium capability. Our location is Dalton Ohio, is there anybody you could refer me to please? I know there is a supplier in Florida that does this medium, but freight is too costly.

I have reached out to some industry contacts. I’m awaiting a phone call. Also a search within the iDirectory revealed no information.

While we’re waiting to hear back, let’s toss this one out the readers too! Is anybody near Ohio running double arch?

— Ralph