Starches, Binders & Paper Bond
Hold the paper-to-core bond through the kiln — and through 30 years of service.
The interface between gypsum core and facing paper is a starch problem. Migratory pregelatinized corn starch travels with the bleed water during setting and deposits at the paper line; non-migratory starch stays in the core and builds compressive strength. Add silicone hydrophobizers, PVA and fiber for water-resistant and Type X cores.
Pregelatinized acid-thinned starches (DE 5–15) dissolve in the slurry, migrate with water, and form a film at the paper-core interface that survives kiln dehydration. STMP-crosslinked starches stay in the core and reinforce inter-crystalline bonds. Silicone emulsions (poly(methylhydrogensiloxane) or PDMS) hydrophobize the gypsum surface; VHI requires under 5% water absorption per ASTM C473.
Paper bond failures are almost always either insufficient migratory starch, kiln overdrying, or paper sizing incompatibility. We map the failure mode to the additive chain before we sell you a product.