Thermal Stress
Structural failure occurs within aqueous coating layers when ice crystal expansion generates internal pressures exceeding local cohesive bonding limits. Freeze-thaw delamination represents this specific mode of structural breakdown in paper and board manufacturing. Converting plants operating in unheated warehouse zones frequently encounter this defect during winter transport cycles.
Moisture trapped inside porous pigment matrices expands upon freezing by nearly nine percent in volume. Subsequent warming melts the ice, leaving microscopic voids that weaken adhesion between the clay coating and the underlying paperboard substrate. Subsequent processing passes force rollers across these compromised zones, causing the weakened coating layer to lift entirely off the paper surface.
Moisture Threshold
Relative humidity levels exceeding critical limits inside stacked pallets create the primary precursor for internal ice formation. Unsealed carton board edges absorb ambient atmospheric vapor rapidly during cold storage transitions. Manufacturers control this vulnerability by applying strict water resistance sizing agents at the wet end of the paper machine.
Laboratory testing subjects coated samples to repeated temperature cycling chambers to measure surface integrity loss. Quantifiable peel resistance values drop sharply once free water accumulates past specific saturation thresholds within the fibrous matrix.
Chemical Mitigation
Synthetic latex binders added to pigment formulations provide the necessary elasticity to absorb volumetric expansion stresses without fracturing. Polyvinyl alcohol additives enhance internal bond strength between mineral pigments and cellulose fibres during extreme temperature drops. Converting operations specify exact binder ratios to prevent coating separation during high speed printing press runs.
Increased binder content reduces porosity, limiting moisture ingress during exterior shipping phases. Finished folding cartons maintain structural integrity only when coating formulations balance pigment volume concentration against available binder coverage.
