Efficient suppression of flammability in wool fabrics via chelation with ferric ions

[Display omitted] •Facile fabrication of flame retardant wool via chelation of ferric ions was developed.•Remarkable enhancement on flame retardancy of wool fabric was achieved.•Metal ions played a vital role in inhibiting the release of smoke for wool fabric.•A two-stage flame retardant mechanism involving the ferric ions was firstly proposed. A facile technique for the fabrication of efficient and durable flame retardant wool fabrics via chelation of ferric ions under mild conditions was developed. The data from limiting oxygen index(LOI) measurements and cone-calorimeter tests (CCT) indicated that the ferric ions not only increased the LOI value from 24.2% to 35.3%, but also decreased the peak heat-release rate and total smoke release value of the wool fabric. Notably, treated wool fabrics also maintained a high LOI value of 28.2% after 30 laundering cycles. Besides, the smoke density of the treated wool fabrics reduced by 60.7%. Moreover, the ferric ions catalyzed the formation of a carbon layer on the wool fibers at a lower temperature and were oxidized and formed a Fe2O3 layer at higher temperatures, which both acted as a protective barrier, cutting off the fuel supply, preventing further burning, and suppressing the release of volatile products.