Substrate Modification Procedure
Mechanical and chemical processes transform treated paperboard into functional packaging containers with specific resistance properties. Barrier board converting involves the application of polymers or aqueous coatings to a base sheet to prevent the migration of oils and moisture. These operations occur on specialized machinery that ensures the protective layer remains continuous across the entire surface.
The process concludes when the board is ready for folding and gluing into a final carton.
Application Technique
Extrusion coating and curtain coating represent the primary methods used to distribute the barrier medium onto the moving web. During barrier board converting, the temperature of the polymer must be high enough to bond with the cellulose fibres but low enough to avoid scorching the substrate. Cooling rolls then solidify the layer to prevent sticking in the finished stack.
Rollers must be calibrated to maintain a uniform thickness and the speed must remain constant because thin spots lead to pinholes that compromise the shelf life of the packaged goods. Precise tension management prevents the layers from delaminating during the rapid changes in speed required for high-volume production.
Finishing Requirement
Die cutting and creasing must be performed with specific pressure settings to avoid rupturing the protective film. If the barrier board converting step produces a brittle surface, the corners of the carton will leak.
