Metal Deposition
Physical vapor deposition coats packaging paper with micro-thin aluminum under high vacuum conditions. Vacuum metallization transforms ordinary folding boxboard into high barrier substrates by vaporizing elemental metal onto moving webs. Chamber pressure drops below one thousandth of a pascal before thermal boats melt the wire feed.
High-velocity vapor clouds condense instantly upon contact with chilled cooling drums. Metallized layers achieve thickness levels measured in nanometers while maintaining flexibility across paperboard fibers.
Barrier Performance
Oxygen transmission rates drop significantly once aluminum crystals seal paper porosity. Water vapor permeability decreases because metal barriers block moisture migration through cellulose networks. Surface energy increases substantially to support subsequent printing and lamination steps.
Coating adhesion depends heavily on primary corona treatments applied before deposition chambers receive the web. Pinholes degrade barrier integrity if particulate contamination remains on base paper surfaces prior to coating runs.
Thermal Reflectance
Radiant heat transfer slows down when metallic surfaces bounce thermal radiation away from packaged goods. Optical density measurements determine aluminum layer thickness through light transmission ratios across finished sheets. Converting lines monitor optical density continuously to keep barrier specifications stable throughout large production orders.
Static electricity accumulation drops during downstream handling because aluminum films dissipate surface charges rapidly. Packaging machinery runs smoothly when metallized paper maintains balanced moisture content alongside metallic coatings.
