Viscoelastic Creep Compliance and Interfacial Fracture Energy in Paperboard Laminates
Creep compliance dictates long-term carton deformation, while interfacial fracture energy governs delamination under score bending and pallet loads.
Micro Stickies Formation
Adhesive Agglomeration
Secondary fibre processing involves the aggregation of pressure sensitive materials into particles that pass through conventional cleaning screens. Micro stickies formation occurs when these small contaminants undergo cycles of shear and heat during pulping or deinking stages. Such particles often originate from hot melt adhesives or latex binders found in recycled newsprint and board stock.
The resulting debris resists standard gravity separation or centrifugal cleaning because the specific gravity of these particles remains close to that of water. Surface tension properties dictate how these residues deposit on paper machine wires or drying cylinders.
Contaminant Dynamics
Mechanical stress applied to waste paper fragments forces synthetic adhesives to break down into smaller units during the stock preparation sequence. Chemical dispersants sometimes unintentionally prevent these fragments from grouping into larger, removable masses. This process creates a distribution of microscopic tackifiers that resist removal by coarse slotted screens.
These particles travel through the whitewater system and attach to mechanical components within the papermaking machinery. Increased operating temperatures in the press section cause these remnants to soften and stick to felt surfaces. The presence of these contaminants leads to web breaks and surface defects on the finished roll.
Operational Mitigation
Effective control of these contaminants requires optimized retention chemistry and carefully calibrated pulper conditions. Targeted removal occurs when mills employ fine slotted screens or flotation cells designed specifically for low density residues. Operators monitor the frequency of machine stops and roll cleaning intervals to assess the effectiveness of these screening strategies.
Strategic selection of feedstocks reduces the total input of pressure sensitive materials into the primary pulper. High concentrations of these particles degrade the structural integrity of recycled fibre sheets over time.