Compression testing is a useful tool to measure performance. It must protect products throughout their entire cycle from the manufacturing plant to the consumer’s hands without over-specification.
Packaging as a protector
During product development, the packaging will be chosen for its ability to protect, preserve and promote. Promotion is typically through colour, shape, and branding. Preservation can be tested through shelf-life trials and on evaluation of the suitability of the packaging to the food. However, when considering how the packaging will aid protection, the movement of the product through the distribution chain must be taken into account. There are several tests that are employed by packaging manufacturers during the design and manufacture of packaging to test its ‘fitness for its purpose. These tests can also be used by food manufacturers and independent test houses as investigatory tools as part of research into packaging performance. One of the tests commonly used in the packaging industry is compression testing.
The resistance to the compressive force applied to a board container is related to a number of factors. Strength properties increase with thickness but can be reduced by an increase in moisture content. All paper and board products will seek to achieve moisture content in equilibrium with ambient conditions. This is known as hypersensitivity. With corrugated containers, the board type and flute type will also influence the strength properties. Corrugated board samples range from the single face (comprised of the one-liner and one flute layer) to triple wall (made up of four liners and three flute layers) with strength increasing respectively. Flutes provide rigidity and can make the board more economical. The flute profile will affect strength; higher flutes (B flutes) provide a physically stronger stack with softer cushioning characteristics. Lower, more dense flutes (E flutes) provide greater flat crush resistance, smoother print surfaces, and crisper score lines. The most common flute type used in the UK is ‘B’.
More and more companies are looking to include higher proportions of recycled content in their packaging, but this too can affect strength. Flute manufactured from the recycled board is used for general performance but when more strength is required or the packaging is to be stored in humid conditions, it is recommended to use virgin material. It is understood that products manufactured from a high content of recycled material boards tend to have an unpredictable structure and inferior functional properties to virgin-based fiber boards.
Compression testing can be a useful tool to measure the performance of packaging. It ensures that products are protected without the packaging being over-specified and therefore unnecessarily expensive. There is hard evidence that performance is linked to the strength properties of a material. In the case of board packaging, strength is increased with thickness, flute type, and the origin of the material. Compression testing can help food and packaging manufacturers select the best packaging for the job. This test can also be used to evaluate the performance of metals, glass, plastic, and composite containers.