Mechanical Greaseproof Paper Grade Selection for Bakeries and Fast Food Packaging
Optimize mechanical greaseproof paper selection by specifying 80-88 SR refining and 15000+ s Gurley porosity to secure non-PFAS grease resistance.
Surface Starch Sizing
Process Purpose
Paper machine coating applications apply film-forming biopolymers to partially dried paper webs to increase surface strength and control liquid absorption. Implementing surface starch sizing at the size press or metering size press bonds loose surface fibres and fills surface macropores on linerboard and printing paper grades. The treatment improves surface pick resistance during offset printing and reduces aqueous ink penetration.
Internal sizing additives applied at the wet end govern bulk water resistance independently of surface treatments.
Application Mechanism
Cooked corn or potato starches are applied to paper webs at concentrations between six and twelve percent solids using roll coaters. During surface starch sizing, starch molecules penetrate the top fibre layers before drying cylinders evaporate remaining moisture and form a continuous surface film. Nip pressure controls starch pick-up rates across the machine width.
Performance Limit
Starch surface films increase surface strength and printing ink holdout but do not provide high barrier resistance against water vapor or fats. Paper mills combining surface starch sizing with synthetic surface sizing agents achieve improved Cobb water absorption values on linerboard grades. Excess starch application increases sheet stiffness and reduces tear strength through matrix embrittlement.
Substrates requiring total liquid barrier performance depend on extruded polymer films or functional dispersion coatings rather than starch surface treatments.