Composite Structure
A structured packaging material consists of several plies of pulp fibers joined together during the wet forming process on the paper machine. In high performance packaging, multilayer cartonboard is engineered to maximize stiffness and thickness while minimizing overall weight. This board structure is designed to provide the physical strength required for transport.
Ply Composition
The distinct layers are formed using different types of pulp to optimize both the cost and the performance of the board. In multilayer cartonboard, the outer plies are typically made from high quality bleached chemical pulp, which provides a smooth, white surface for high resolution printing. The middle plies are composed of cheaper mechanical pulp or recycled fibers, which add thickness and stiffness without increasing the weight.
This three ply or four ply structure behaves like an I beam, where the outer layers handle the tensile and compressive forces.
Converting Efficiency
This structural design is highly valued by converters who need stiff cartons that do not bulge or crush when stacked on pallets. High stiffness is essential for automated filling lines, where cartons must be opened, packed, and sealed at high speeds without bending or jamming. By using different pulp types in each layer, manufacturers can tailor the board to specific requirements, such as moisture resistance or food contact approval.
This makes the board highly versatile for a wide range of retail packaging applications.
