Material Composition
Packaging substrates manufactured from reclaimed secondary fibres represent a major category of sustainable materials for industrial and consumer goods. A standard recycled packaging board relies on recovered paper that is repulped and formed into a multi-ply sheet. This process yields a layered structure with shorter fibres.
Structural Strength
The reduced average fibre length in reclaimed pulp affects the mechanical properties of the finished sheet. Multiple recycling cycles degrade the bonding capability of cellulose fibres, which leads to lower tensile strength and lower bending stiffness than equivalent virgin grades. To achieve the same packaging performance, a recycled packaging board must be produced at a higher basis weight and thickness than a board made from virgin kraft pulp.
This increase in thickness helps offset the lower intrinsic strength of the recycled fibres, allowing the box to withstand stacking loads in warehouses.
Surface Finish
Secondary fibres contain remnants of ink and adhesives that can cause surface imperfections during the sheet forming process. Mills apply mineral coatings or a top layer of bleached chemical pulp to hide these contaminants and provide a uniform surface for printing. Inks printed on this surface must dry through a combination of absorption and oxidation, which can be influenced by the porosity of the underlying recycled sheet.
Starch and sizing agents are often added to the surface of the recycled packaging board to control this porosity, preventing excessive ink absorption and ensuring sharp image resolution.
