Corrugated
A versatile paper-based material used for sturdy packaging.
- Also Known As
- Corrugated Cardboard
- Corrugated Fiberboard
- Combined Board
Corrugated board is a sturdy packaging material made with fluted corrugated medium glued between one or two flat liners. The interior layer, called corrugated medium, is wavy to provide the cardboard its strength. Various sizes of the wave, called flutes, determine the degree of strength.
Containerboard is a type of paperboard specifically manufactured for the production of corrugated board. Different grades and basis weights of containerboard make the corrugated medium and liner. The corrugated medium gets glued to the liner using a starch-based adhesive.
By specifying the liner, flute size, corrugated medium, board construction, strength, and print, corrugated packaging can be engineered with specific properties for a variety of use cases. Thus, it is one the most versatile packaging materials available.
Liner
- Also Known As
- Linerboard
A liner is a containerboard, usually at a lower caliper of 12pt, that is used as an inner or outer facing in the manufacture of corrugated board. Traditionally, a liner containing at least 80% virgin pulp fibers is called kraft liner, and anything less is called test liner. This distinction is no longer widely used in the US as liners can have up to 100% recycled content. General rule of thumb: whiter the liner, the less recycled content it contains.
Paperboard grades used for folding cartons can be used as liner for high-graphic prints.
Flutes
- Also Known As
- Corrugation
Flutes are wave-shapped patterns and come in various sizes. The smaller the flute size, smoother printing surface and higher puncture resistance. The larger the flute size, greater the strength and better the cushioning. Flutes are measured by the number of flutes per foot of liner. A corrugated medium is the container board used to create flutes.
| Flute | Thickness | Flutes / Foot | Use Cases |
|---|---|---|---|
| F | 1/32" 0.8mm | 125 ± 4 | Shoe Boxes |
| E | 1/16" 1.6mm | 90 ± 4 | Pizza Boxes |
| B | 5/32" 3.2mm | 47 ± 3 | Mailer Boxes, POP Displays |
| C | 1/ 8" 4.0mm | 39 ± 3 | Standard Shipping Box |
| A | 3/16" 4.8mm | 33 ± 3 |
Approximately 80% of corrugated boards are C flutes. There are other flute sizes, but these are the most frequently used. Flutes were named when invented; thus, when listed alphabetically it does NOT correlate with the size of the flute.
Board Construction
Strength Test
Arguably the most important purpose for corrugated packaging is to ensure boxes can withstand handling during shipping and transportation. There are two tests, Edge Crust Test and Mullen Test, that measure the strength and durability of a corrugated boards. Both tests tell you how much pressure your box can take before it breaks, but each test the material in a separate way.
Whichever measurement is used, the paper basis weight and flute size are the most important performance indicators.
32 ECT and 200#, comparable in strength, is the most commonly sold corrugated box. This means a "standard" box can hold up to 30-65 lbs of products, depending on how the product is packed. Below are suggested load recommendation for single wall boards.
| Load / Box | Min. ECT | Mullen Test |
|---|---|---|
| 35 lbs | 26 ECT | 150# |
| 50 lbs | 29 ECT | 175# |
| 65 lbs | 32 ECT | 200# |
| 95 lbs | 44 ECT | 275# |
| 120 lbs | 55 ECT | 350# |
Custom Printing
There are various ways to get custom artwork on corrugated boards: direct print, pre-printed liner, litho-lamination, and litho label. Given the wide range of packaging that corrugated boards produce, multiple printing options are available to make exceptional packaging.
Not all printing options are available by all manufacturers. Direct print with flexography is the most common printing method and widely available. For pre-print liner and litho-lamination, fewer manufacturers have the required machinery, which contributes to the long lead times and high MOQs.