35—IMPROVEMENT OF THE NATURAL FLAME-RESISTANCE OF WOOL. PART IV: WOOL-RICH BLENDS WITH POLYESTER FIBRE AND NYLON

Wool-polyester-fibre and particularly wool-nylon blends show a significant negative deviation of limiting-oxygen index (LOI) from the average, calculated values. This is probably due to the higher heat of combustion and lower LOI of polyester fibre and particularly of nylon when compared with wool.

Consequently, wool-rich blends with nylon are more difficult to flame-resist-treat with metal complexes than wool-polyester-fibre blends. In the former blend, at least 75% flame-resistant wool and in the latter blend 60–90% flame-resistant wool has to be present to enable flame-resistant wool-rich blends to be obtained, the exact amount depending on the fabric construction. The hexafluorozirconate treatment is effective on blends containing at least 85% wool, whereas zirconium-tungsten complexes have to be applied for blends with lower wool contents.