Corona Decay Kinetics and Solventless Adhesive Wetting in Polypropylene Lamination
Corona decay on polypropylene impairs solventless adhesive wetting, requiring in-line treatment to maintain dynamic surface energy above 40 dyn/cm.
Washburn Capillary Flow
Fibre Porosity
Fluid migration across a porous substrate depends directly upon Washburn capillary flow to drive liquid into the interstitial voids of paper and board. Pores inside a sheet act as bundles of microscopic tubes where surface tension pulls moisture inward without external pressure. Converting lines monitor this movement because rapid liquid uptake dictates how fast printing inks anchor onto offset stocks or how uniformly barrier coatings penetrate raw linerboard.
Contact angle and surface energy determine the rate of penetration once liquid touches the dry surface. Variations in refining intensity alter pore radii directly, slowing or accelerating absorption across the web.
Coating Defect
Surface absorption kinetics govern whether liquid coatings remain uniform or sink too deeply into porous paperboards. Excessively rapid liquid uptake causes binder migration toward the interior, leaving the surface starved and weak for subsequent printing passes. Converting machinery applies aqueous sizing formulations that must stay on the top layers to preserve gloss and ink holdout.
Adjusting the viscosity of the applied fluid counteracts extreme absorption rates during high speed blade coating operations. Uneven void distribution across a reel causes localized blistering when moisture evaporates irregularly from the internal structure.
Wetting Dynamics
Contact mechanics describe the interaction between liquid droplets and solid cellulose networks during converting processes. Initial spreading precedes bulk liquid uptake whenever dampening solutions contact dry paper webs on printing presses. Surfactants modify the surface tension of water based fluids to accelerate penetration into tightly calendered sheets.
High porosity allows faster adhesive penetration during corrugated box assembly, improving bond strength before green strength fails. Temperature changes alter fluid viscosity and modify the final absorption depth within packaging laminates.