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glossary/nssc

NSSC (neutral sulfite semichemical)

Also: NSSC, neutral sulfite semichemical, semichemical

Semichemical pulp made from hardwood with a mild sulfite pretreatment followed by mechanical refining. The standard furnish for virgin fluting.

NSSC pulping cooks hardwood chips (birch, oak) in a mild sodium sulfite solution at near-neutral pH, which softens the lignin without fully dissolving it. The softened chips are then mechanically refined. Yield is 75 to 85%, between chemical and mechanical routes.

NSSC fluting has higher stiffness and CMT than recycled fluting at equal grammage. Most European and US virgin fluting mills use NSSC. Hardwood is essential: the short, stiff hardwood fibers give the characteristic flute crush resistance.

Related
  • Kraft pulp. Chemical pulp produced by cooking wood chips with sodium hydroxide and sodium sulfide. The dominant pulp process globally.