Tack Window
Temporal window defining the maximum duration an applied adhesive film remains sufficiently tacky and fluid to form an acceptable fiber-tearing bond upon mating. High-speed folding carton convertors monitor folder gluer open time to ensure wet glue dots wet out opposing board faces before initial compression. The parameter measures the interval between adhesive deposition from a nozzle or wheel and the instant moisture loss or cooling renders the surface inert.
Beyond this operational limit, partial skinning prevents total interfacial contact, producing weak glue joints that fail under structural box tension. The boundary applies strictly to the uncompressed state of the open blank prior to entering the compression belt.
Compression Boundary
Ambient temperature, relative humidity and board surface porosity directly alter the rate of solvent penetration into paperboard fibers. High substrate absorbency shortens the available window by drawing water rapidly out of aqueous emulsion formulations. An extended folder gluer open time accommodates long blank transfer distances on slow folding lines, preventing premature film drying before flaps overlap.
Conversely, rapid drying formulations prevent adhesive migration into unprinted reverse folds during high-speed production runs. Machine operators adjust application volumes and nozzle positioning to match line speeds with the dynamic drying rate of the selected adhesive formulation.
Setting Velocity
Excessive open durations cause adhesive squeeze-out under final compression belts, transferring wet glue onto transport ribbons and contaminating adjacent cartons. Formulations tailored for short transfer zones set rapidly, establishing structural tack within fractions of a second.
