Meaning
Coating processes depend on the continuous displacement of air by a liquid film on a moving substrate. Dynamic wetting failure occurs when the substrate speed exceeds a critical limit, causing air to be trapped between the liquid and the solid surface. This phenomenon creates voids and uneven film thickness that ruin the coating quality.
Velocity Boundary
Industrial coating lines seek to maximize line speed to achieve high throughput. Encountering dynamic wetting failure during high-speed runs indicates that the surface tension or viscosity of the liquid is incorrectly balanced for the target rate. Running pilot trials on narrow webs often fails to predict this failure because edge effects differ on wider production lines.
Wetting Audit
Identifying the onset of air entrainment requires inspecting the coated substrate using high-speed optical scanners or laser reflection sensors. Measuring the contact angle under dynamic conditions provides a baseline for safe operating speeds.
Throughput Loss
Pushing line speeds beyond the dynamic wetting limit without adjusting the coating formulation leads to massive scrap generation. Entire rolls of paper or polymer film must be discarded if the adhesive layer contains microscopic air pockets. The cost of solvent recycling and raw material waste heavily damages the production economics.
