Surfactant Migration Impact on Dynamic Surface Tension in Hardwood Stock
Residual surfactant migration in hardwood stock depresses dynamic surface tension below forty millinewtons per meter, triggering jetting print defects.
Boundary Pinning Failures
Wetting Mechanism
Wetting phenomena occurring at the microstructural level describe the immobilization of a liquid droplet edge on a solid substrate during the drying or spreading process. These boundary pinning failures arise when topographical irregularities or chemical variations on the paper surface prevent the contact line from moving smoothly. Printing quality depends on a predictable expansion of the ink droplet across the fibres.
Physical Obstruction
Surface roughness often creates physical barriers that trap the advancing front of a coating or ink. When a substrate exhibits extreme peaks and valleys, the liquid cannot overcome the energy barrier required to reach the next equilibrium state, leading to boundary pinning failures. This localized stalling results in uneven ink distribution and jagged edges on printed characters.
Production Impact
High-speed printing lines suffer most from these disruptions because the window for fluid stabilization is exceptionally narrow. Substrates with poorly controlled surface energy or inconsistent sizing agents show a higher frequency of boundary pinning failures. Corrective measures involve increasing the smoothness of the base sheet or adjusting the surfactant package in the ink to modify its dynamic behavior.
Manufacturers monitor the frequency of these events to ensure that coating formulations provide a uniform wetting profile across the entire width of the web.