Viscoelastic Property Loss in Aqueous Coated Paperboard Converting
Moisture and thermal stress during converting plasticize aqueous latex coatings, reducing storage modulus and causing fold delamination unless web tension is optimized.
Chill Roll Quenching
Thermal Rate
Extrusion coating lines employ rapid thermal shock to freeze molten polyolefin resin onto paperboard substrates immediately after leaving the die gap. In chill roll quenching, temperature differential between the steel roll face and the polymer layer determines the rate of solidification and the resulting adhesion strength. The process stops governing polymer structure once the web leaves contact with the cooling drum.
High roll temperatures yield slow cooling, which promotes polymer crystallization and weakens fiber mechanical bonds.
Extrusion Boundary
Internal web tension maintains mechanical contact across the roll face to prevent air entrainment during high speed web passage. When line speeds exceed four hundred meters per minute, boundary air layers can lift the web, producing localized cooling gaps and density variations. Adjusting the air knife nip pressure eliminates boundary air entrapment and stabilizes contact.
Polymer Crystallinity
Rapid surface cooling suppresses large spherulite growth within low density polyethylene coatings, preserving film clarity and pinhole resistance. Non-uniform quenching generates residual internal stress within the extruded film, leading to curl or edge lifting on folded carton blanks. Precise temperature control of internal cooling water loops maintains uniform heat transfer across the entire roll width, protecting dimensional stability across wide paperboard webs.