Material Composition
Paperboard manufactured primarily from recovered paper fibres is formed into the wave-like middle layer of corrugated shipping boxes to provide compression resistance. This recycled fluting medium utilizes old corrugated containers and mixed waste papers as its primary raw material. The sheet is engineered to maintain high stiffness and crush resistance despite the shorter fibre length of recycled pulp.
It represents a cost-effective alternative to virgin semi-chemical fluting in secondary packaging.
Mechanical Resistance
Strength of the structural board depends heavily on the resistance of the corrugated arches to flat and vertical loads. In a finished box, recycled fluting medium is evaluated using the Concora Medium Test and the Corrugated Fluting Crush test. These methods measure the ability of the formed flutes to resist collapse during handling and stacking.
Since recycled fibres have lower intrinsic bonding strength, mills often add starch or dry-strength agents to the pulp to meet specifications. This chemical treatment compensates for the shorter fibre length of the recycled furnish.
Converting Process
Corrugating machines heat and moisten the flat sheet before it passes through the corrugating rolls to shape the flutes. When processing recycled fluting medium, control of the steam showers is critical to avoid cracking the dry sheet. The formed flutes must immediately receive adhesive on their tips to bond with the linerboard.
This step completes the rigid sandwich structure.
