Archive for the ‘Containerboard’ Category

Insulating Properties of Corrugated

August 15, 2019

Rich asks,

I have a question about the insulating properties of corrugated and the impact of vent holes in dairy applications. I have a dairy customer who is looking to pack sour cream in cartons. It is filled at 100 degrees F and put into 35 degree refrigeration. What is the difference in how long it will take to get down to 40 degrees if there are no vent or hand holes in an RSC against if there are some? Is there a formula that exists for the cooling time? This would be an ECT48 DW RSC. Thank you as always for your guidance.

Here is a link to a research paper (Overall Effective Thermal Resistance of Corrugated Fiberboard Containers) complied by the US Dept. of Agriculture and the Forest Products Laboratory. Pages 4 – 6 of this report contain information regarding the affect of vent holes.

The location and area of the vent holes as well as the velocity of the circulating air will also have an affect on the thermal transition time.

Would it be possible to perform an experiment using a grill or meat type thermometer to determine when the core of a loaded box with vents and a loaded box without vents reached the desired 40 degrees F?

— Ralph

Tests for Quality of Board

August 14, 2019

Harendra asks,

We are in the process of evaluating the quality of OCC grade 11 & 12. Can you suggest what specific test should be performed for quality evaluation of these two grades for production of container boardpaper?

I would suggest contacting Bill Moore at Moore Associates in Atlanta. He is an expert in this area.

Moore & Associates
Phone: (770) 518-1890
www.marecycle.com/

— Ralph

Convert European Board Specs to ECT

August 14, 2019

Jeff asks,

We have a customer that is based in Germany and is opening a branch in Tennessee.

They gave us some specs with the below board grades:

2.91BCB (alternative 2.91 AC)

2.70BC

2.91ACA

2.30BC

1.40C

We need to convert them to ECT values.

Do you have any information on how I can convert them?

 

Jeff, usually the metric equivalent to our pounds force per linear inch is expressed in kN/m but in this case I believe we are looking at kg-f/in so you need to divide their requirement by 0.038 to obtain the equivalent Imperial value. We have compiled a list of conversions that you may find helpful. (English Metric board conversions)

Conversions for grades listed above would be,

2.91BCB (alternative 2.91 AC)   — 76 ECT BCB Triplewall or AC Doublewall

2.70BC — 71 ECT BC Doublewall

2.91ACA — 76 ECT ACA Triplewall

2.30BC — 61 ECT BC Doulbewall

1.40C — 37 ECT C Singlewall

— Ralph

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