Is Your Corrugated Stored Correctly?
Moisture and heat are the two environmental factors that can create the most trouble for corrugated. Warehouses are seldom climate-controlled. As temperatures rise and fall throughout the day, the humidity in the warehouse or even the trailer can fluctuate widely. Changing seasons can have an impact, too. In arid and humid climates, the relative humidity can be vastly different between them. Understanding how the environment impacts your corrugated boxes will help you make decisions to ensure your boxes don’t fail.
Other environmental factors include storage time under load, how they are placed on a pallet, and excessive handling.
Relative Humidity
There is a direct relationship between moisture and temperature when it comes to relative humidity. Humidity is the amount of water vapor present in the air. The air can only hold a specific amount of moisture, and that changes based on temperature. Relative humidity is the ratio of water vapor present in a given volume of air at a specific temperature – this is expressed as a percent. Colder temperatures hold less moisture. This is why we see dew in the evenings as it gets cooler.
Corrugated is made up of a fluted medium sandwiched between two linerboards with adhesive. These materials are hygroscopic, meaning they have an affinity for moisture. In humid environments, corrugated board soaks up moisture until it reaches an equilibrium – the point that no more moisture can be absorbed in the given temperature and humidity.
Why Moisture Should be Regulated
When corrugated sheets are made, water is used in the manufacturing processes, but the sheets are dried during the heating and curing process. The moisture content must be controlled to avoid warping, which can negatively impact box manufacturing. It can also lead to delamination, poor creasing, printing challenges, among other issues.
Even after the boxes are made, moisture needs to be maintained, or stacking strength will be diminished. Both high humidity and low humidity can create issues.
Too high and corrugated fibers can loosen, glue bonds can weaken, and delamination can occur. Too low, and the corrugated board and glue can dry out and crack.
It isn’t feasible to have a controlled environment for most, but exposing corrugated boxes to fluctuating humidity should be avoided.
Compression Strength and Environmental Multipliers
It is possible to estimate the impact that environmental factors will have on the container strength. When the compression strength is known, you can use accepted multipliers to get an estimate of safe stacking load for a group of boxes. The time boxes are stored under load impact their strength. After 90 days, a box loses 45 percent of its compression strength, and having a high relative humidity impacts it even more. The chart below from the Fibre Box Association gives the multipliers for storage under load and relative humidity under load. Notice that cyclic relative humidity increases it even more.
|
Environmental Factors |
Compression Loss |
Multipliers |
|
Storage time under load |
10 days – 37 percent loss |
0.63 |
|
30 days – 40 percent loss |
0.60 |
|
|
90 days – 45 percent loss |
0.55 |
|
| 180 days – 50 percent loss |
0.50 |
|
|
Relative humidity, under load (cyclical RH variation further increases compressive loss) |
50 % RH – 0 percent loss |
1.00 |
|
60 % RH – 10 percent loss |
0.90 |
|
|
70 % RH – 20 percent loss |
0.80 | |
| 80 % RH – 32 percent loss |
0.68 |
|
|
90 % RH – 52 percent loss |
0.48 |
|
| 100% RH – 85 Percent Loss |
0.15 |
Pallet patterns, whether columnar (aligned or misaligned) or interlocked, overhang, and the gaps between the pallet boards, and excessive handling also reduce compression strength.
|
Environmental Factors |
Compression Loss |
Multipliers |
|
| Best Case |
Worst Case |
||
| Pallet Patterns | |||
| Columnar, Aligned | Up to 8 percent loss | 1.00 | 0.92 |
| Columnar, misaligned | 10-15 percent loss | 0.90 | 0.85 |
| Interlocked | 40-60 percent loss | 0.60 | 0.40 |
| Overhang | 20-40 percent loss | 0.80 | 0.60 |
| Pallet deck board gap | 10-25 percent loss | 0.90 | 0.75 |
| Excessive handling | 10-40 percent loss | 0.90 | 0.60 |
Consider Axis Corrugated
As a privately held independent corrugator, we strive to deliver cost savings through shorter lead times and optimized packaging that best fits your needs. If you have had it with long lead times, low quality, and slow response time, give us a call and let’s get started on unfolding endless possibilities.