Fibre Grade
High yield lignocellulosic material produced through a combination of thermal and mechanical processing assisted by chemical pretreatment provides a balance between bulk and brightness. In the hierarchy of papermaking fibres, bleached chemithermomechanical pulp represents a middle ground between chemical pulps and purely mechanical varieties. It undergoes a mild chemical pretreatment, often with sodium sulfite, followed by pressurized refining to separate fibres without destroying the lignin.
The resulting pulp is then bleached to high brightness levels while maintaining the stiffness required for folding boxboard.
Material Property
Stiffness and bulk dominate the performance profile of this fibre grade. Bleached chemithermomechanical pulp creates a voluminous structure that increases the distance between the outer plies of a multi-ply board. This geometry enhances the bending resistance of the final substrate.
High freeness values in the pulp allow for rapid drainage on the wire, which supports faster machine speeds during production. The structural resilience of the individual fibres prevents the collapse of the sheet during the pressing stage of the papermaking process. This retention of volume ensures that the finished board maintains a thick caliper without a proportional increase in weight.
Industrial Application
Packaging manufacturers rely on the compressive strength of the lignin-rich fibres to maintain carton integrity. Because bleached chemithermomechanical pulp retains most of the wood substance, it offers higher yield than kraft pulp. Modern bleaching sequences using hydrogen peroxide mitigate the tendency for yellowing for most retail packaging lifecycles.
