EFFECTS OF SPINNIG AND HEAT-TREATMENT CONDITIONS ON THE CROSSLINKING OF POLY (VINYL ALCOHOL) FIBERS WITH FORMALDEHYDE

Abstract

Formation of cross-links (intermolecular formal bonds) in the heterogeneous formalization of poly (vinyl alcohol) (PVA) fibers obtained by various spinning methods and heat-treatments under various conditions was examined by means of the solubility test.
The cross-link content of the formalized products from the unoriented fibers decreases slightly with a rise in the temperature of heat-treating under constant length. For the drawn fibers the cross-link content decreases with increased draw ratio. In the drawn fibers heat-treated under the condition where small shrinkage is allowed, the cross-link content is nearly the same as that of the as-drawn fibers, but the heat-treatments with higher shrinkage ratio result in the increase of the cross-link content of the formalized products, and the cross-link content also varies with spinning conditions.
The difference of reactivity to crosslinking of PVA fibers spun and heat-treated under various conditions may be related to the facts that the rate of crosslinking, the rate of hydrolysis of the intermolecular formal bonds or the ratio of the rate of intermolecular formalization to that of overall formalization are affected by the fine structure of the samples.