Phase Transition
The irreversible thermal disruption of semi-crystalline polysaccharide granules suspended in an aqueous carrier yields a cohesive, viscous adhesive matrix. Corrugator single-facers and paper mill wet ends induce starch gelatinization to convert native corn, wheat or tapioca starch slurries into functional bonding agents. The hydrothermal conversion initiates only within an exact temperature and moisture window, unwinding amylose and amylopectin molecules into surrounding liquid.
Dry thermal processing without excess moisture fails to trigger this conversion, causing molecular degradation instead of hydration swelling.
Bonding Thermodynamics
Raw starch granules absorb ambient water within the carrier suspension while corrugator steam chests apply conductive heat. As temperature climbs past the thermal threshold, water molecules break intermolecular hydrogen bonds inside the starch granule matrices. Individual granules swell rapidly, consuming surrounding free liquid and drastically increasing slurry viscosity along the fluting tips.
Dissolved amylose chains leach into the aqueous matrix, penetrating into porous outer linerboard cellulose networks. Compression rolls force the swelling paste into intimate contact with paper fibers before heat drives off water to complete crystallization. Deficient thermal input produces green bond failures, letting linerboards delaminate cleanly without fiber tear.
Excessive early temperatures trigger premature thickening in distribution pans, starving applicator rolls of uniform glue volume.
Thermal Window
Gelatinization onset requires wet fluting tip temperatures between sixty-five and seventy-two degrees Celsius, depending on the chemical modification and botanical source of the base starch. Incomplete thermal activation yields unbonded corrugated board flutes that peel without tearing structural liner fibers.
