Rapid permanent setting of wool fabrics by conductive heat transfer

High levels (50–70%) of permanent set were obtained when wet pure wool fabric was heated rapidly to 110–130°C for up to 1 minute under conditions that limit the evaporation of water. If the final regain of the fabric after treatment was less than 34%, lower levels of permanent set were generally observed. If the initial regain was less than 34%, permanent set levels were invariably <20% and the specimens were usually damaged by scorching due to the low heat capacity and poor thermal conductivity of wool compared with water. This result precludes the use of a rapid chemical-free permanent setting process based on conductive heat transfer at the dry finishing stage. Under more severe conditions (higher temperatures or longer pressing times) significant shrinkage, yellowing and fabric damage due to supercontraction were observed. The high level of permanent set obtained in this study suggests that the performance of continuous crabbing machines could be improved by optimizing the treatment conditions without the need for chemical setting agents.