Polyisocyanate Shrink‐resist Treatments for Wool: A Mechanistic Study

Abstract

The Flory‐Stockmayer approach to polymer gelation or network theory has been applied to the moisture curing of polyisocyanates used to shrink‐resist wool. This predicts that polyisocyanates of functionality f gel at an extent of reaction of(f‐l) ‐1 . This was confirmed experimentally and the relation was shown to be independent of the initial concentration of water and the presence of catalysts. The development of shrink‐resistance on wool treated with polyisocyanates has been related to their gel‐point and the extent of crosslinking after gelation. The properties of wool treated with some di‐ and tri‐functional polyisocyanates have been compared and the results interpreted using network theory and kinetic factors involved in the curing reaction. The optimum functionalities for use on wool of polyisocyanates derived from polypropylene oxide polyols and various di‐iso‐cyanates are discussed.