Formaldehyde Curing of Zein Fibers

Abstract

Conditions necessary for the rapid formaldehyde curing of zein fibers were investigated and a continuous two-stage curing process was developed. The first stage (precuring) consists of a mild cure to introduce approximately 0.75 percent formaldehyde into the fiber and produces, after stretching, a fine-diameter fiber of exceptional strength and elasticity. The second stage (post-curing) consists of a strong cure to introduce about 3.0 percent additional formaldehyde into the stretched fiber to stabilize its length. Formaldehyde is bound under both alkaline and acid conditions, but it is only under acid conditions that any curing occurs. Ammonium salts act as catalysts for the reaction in the pH range 0 to 4 and the resulting fibers are stable to boiling in mild alkali. When cured under highly acidic conditions (below pH 0), the fibers are stable to both acid and alkaline boiling.