Thermal Evaporation
Radiation heat transfer accelerates liquid vehicle removal from aqueous coatings and flexographic inks positioned on moving paperboard webs. Electromagnetic emitters placed directly after coating stations generate radiant energy in short or medium wavelengths to excite water molecules within wet films. On packaging press lines, inline infrared drying raises film temperature rapidly to initiate rapid phase changes without overheating underlying cellulose fibres.
The operational boundary ends where coating moisture reaches solid equilibrium, beyond which added radiant energy causes thermal blistering.
Wavelength Matching
Medium-wave emitters match the absorption peak of water, maximizing thermal energy absorption while preventing surface skinning. Short-wave systems penetrate deeper into thick liquid coatings, heating the substrate interface to drive water upward through the film. Air extraction knives situated beside emitter banks strip saturated boundary air, maintaining moisture gradients necessary for continuous mass transfer.
Insufficient air movement leaves vaporized water near the sheet surface, retarding evaporation and wasting electrical energy. Temperature sensors continuously feed web thermal data back to power controllers, adjusting emitter output as press speeds fluctuate.
Substrate Response
Excess radiant heat dries paperboard fibers prematurely, causing edge curling and dimensional instability during subsequent die-cutting steps. Controlled thermal application preserves board moisture balance, ensuring flat sheets for smooth downstream converting.
