About Corrugated Packaging

The Strengths of Corrugated

The excellent rigidity and structural strength of corrugated board arise from its construction - the familiar fluting medium held between flat liners.

Recent developments in flute sizes and combinations, and the varieties of paper types and finishes have opened up a whole new range of possibilities for this versatile material.
Simplicity and integrity are the real strengths of corrugated packaging. Fluting, fixed between the inner and outer liner, gives unique cushioning characteristics and also achieves excellent rigidity and structural strength.

Over the decades, successive generations of improvement have established a range of products for different applications. Standard and non-standard categories of corrugated packaging are based on the type of flute, whether coarse, fine or extra fine and the number of fluted tiers, whether single, double or triple tiers.

The standard range includes the coarse ‘A’ and ‘C’ flute, fine ‘B’ and extra fine ‘E’ and ‘F’ flutes. The ‘B’ flute is the most widely used. It is very robust (difficult to crush) and has good compression strength. It is also compact, so less space is required during transit or storage. The ‘C’ flute is larger with greater compression strength but offers less crush resistance and requires more space.

The latest construction is the ‘N’ flute, which is 48 per cent thinner than ‘E’ fluting and 20 per cent thinner than the ‘F’ flute. This new ‘N’ flute looks set to open up a large potential market for more sophisticated packaging. The non-standard range includes mini and micro ‘F’ flutes.Flutes come in different combinations: single-face web, single-wall board with single or dual-arch fluting and double and triple walls. Double wall packaging combines ‘B’ and ‘C’ flutes, for applications where compression strength is more important than storage space. More recent innovations have combined ‘E’ and ‘F’ flutes. Triple wall is a more rigid board that provides excellent stacking strength with good shock and puncture resistance.

Just as there are different types of construction, there are many types of paper used in the components of corrugated packaging. The outer surface can be made from virgin ‘Kraft’, or more usually ‘test liner’ which is composed of recycled fibres. It can be brown or bleached white for printing, white (outside) and brown (inside) for improved economics; or be made from a mixture of recycled waste and pure wood pulp.

Fluting is made from two processes, which use different formulations of chemicals, recycled paper and starch to produce different grades of flutability.

To ensure corrugated packaging offers predicable performance, the industry has established a series of tests. These are far more numerous than you might imagine.

‘Edge Crush’ and ‘Box Compression’ determine the reliability of the packaging in stacking. Other tests such as ‘Ring Crush’ and ‘Flat Crush’ examine the structural qualities of the paper, board and complete box. Caliper and flute height measure the most important component dimensions. The ‘Mullen Burst’ test measures resistance to pressure and tearing strength. ‘Puncture Test’ measures resistance to a sharp object and ‘Slip Angle’ measures the coefficient of friction to ensure surfaces are not too slippery, ensuring reliable stacking properties during transit.Other tests measure water and moisture resistance and porosity. These relate to printing performance, the suitability for carrying fresh produce and the distortion likely to be caused by moisture. Porosity determines how well packaging can be handled by suction on vacuum fed handling equipment. Other tests explore chemical composition and more specific mechanical properties such as susceptibility to vibration.

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