Strong insect-resist property and wash-durability exhibited by wool fabric sustainably treated with a natural diterpenoid and a synthetic pyrethroid under subcritical CO₂

To conserve wool textiles from insect attack, they are frequently treated with emulsions of natural and synthetic pyrethroid in an aqueous medium. Although the treatment is highly effective, it produces toxic effluent. In this work, insect-resist wool fabrics were produced by treating them with a natural diterpene (totarol), and a synthetic pyrethroid (permethrin) in a subcritical carbon dioxide (subc-CO₂) medium. The totarol treatment failed to provide any insect-resist activity but the permethrin treatment even at 0.03% on the weight of wool fiber (owf) showed excellent insect-resist properties and the mortality of the larvae was more than 98%. The wool fabrics treated with permethrin at 0.03% owf under subc-CO₂ only marginally lost insect resistance after 20 washes (equivalent to 80 domestic washes) but at 0.09% owf, still, the mortality of larvae was more than 98%. However, the fabric treated with 0.05% owf by the traditional aqueous treatment completely lost its insect-resistance property after 5 washes. The Soxhlet extraction of permethrin with dichloromethane from the treated fabric and GC-MS analysis of the extracted permethrin suggest that most of the permethrin was absorbed into the wool fiber. The developed process could be a durable and sustainable treatment for the conservation of wool textiles.