Paperboard Category
Packaging substrates manufactured specifically for conversion into corrugated shipping containers form the primary structural raw material in board converting plants. The umbrella designation containerboard covers both facing liners and fluting media used in corrugated board assembly. Heavy kraft pulps or recycled fibers provide the necessary stiffness and tensile performance for outer plies.
Semi-chemical hardwood pulps give internal fluting its compression resistance. Modern converting lines run these grades at high speeds to form rigid structural fluting architectures. The classification ends where solid bleached folding boxboard, grey chipboard, and liquid packaging substrates begin.
Component Function
Facing sheets must maintain flat geometry under ambient humidity shifts. Outer linerboard layers resist tensile forces during bending and absorb print inks without excessive show-through. Inner fluting holds opposing liner sheets at fixed spacing to maximize beam strength.
Combined containerboard structures achieve high strength-to-weight ratios compared with solid wood or plastics.
Recycled Fraction
Mixed paper waste supplies an increasing proportion of raw fiber for modern paper machines. Secondary pulping systems produce containerboard grades by fractionating waste streams and adding chemical strength agents. Short fiber content reduces tensile strength, requiring starch spraying during sheet formation.
Moisture content adjustments at the paper machine dry end prevent warp during corrugator combining operations. Converting operations adjust adhesive application rates when processing high-recycled containerboard grades.
