Corrugated Sheet

The strength of a corrugated box starts with its material. A corrugated sheet consists of two major components - linerboard and medium. Linerboard is the flat paper that covers both sides of the sheet and the medium is the "fluted" or arched paper found between both liners. The flute, when anchored to the linerboards with a starched-based adhesive, resists bending and pressure from all directions. When placed vertically on its ends, the flutes form vertical columns, capable of supporting considerable amounts of weight.

Flutes

The “Flute” describes the structure of the wave shaped medium liner material between two liners that makes up a board’s corrugation. Flutes come in five basic sizes, known as flute profile. The most common are "B-Flute"(used for die-cut boxes) and "C-Flute (used for RSCs). B-flute is compressed and appears thinner. However, it is made with more paper to provide stronger side wall protection from blows and punctures. C-flute is taller, with more air space, but offers enhanced stacking strength. For excellent graphic reproduction, consider E-flute.

When you are choosing a box for your project, using the right flute is an important factor. The following are the three basic flutes and their advantages:

Corrugated Fibreboards

We manufacture two basic types of corrugated fibreboards: Single Wall and Double Wall

These fibreboards are built from a combination of flutes. Each one having their individual strengths and advantages to your demand and specifications.

Mullen Test

The Mullen test or the Bursting Test is a measurement of box strength. It measures the resistance to rupture in pounds per square inch (psi). Linerboard constitutes bulk of the bursting strength of a corrugated sheet. The basis weight of the paper as measured in lbs/1000 sq. ft. directly impacts paper strength. Another alternate rule for box strength, which measures the characteristics of stacking strength of a box is the Edge Crush.

Edge Crush

Edge Crush (ECT) measures the ability of combined board to sustain a top-to-bottom load. The strength is directly related to the compression strength of both the liners and medium. Box compression strength is the maximum load a given box can stand for a moment. Stacking strength is the maximum load a box can stand throughout the distribution cycle. This means that the bottom box must support the top load over a period of time in which it may be exposed to fluctuations in temperature and humidity as well as other factors that impact performance such as handling, pallet patterns, pallet deck board spacing, and overhang.

The following chart shows Bursting Test and Edge Crush Test performance standards of corrugated box liners based on the combined weight of a box and its contents.

It is important to understand that whichever measurement you prefer to use to measure box strength, basis weight and flute size are the two most important for the best box performance and raw material quality.

When designing a packaging solution, the best designers begin with the end in mind. Every packaged product has its own unique set of problems to solve. These include physical characteristics of the product, the mode in which the package will be shipped or stored, and the functions the package will be asked to perform.

Burst strength is more relevant when product containment or puncture resistance is the main concern. ECT is more relevant when stacking strength is the main concern.