Flame-retardant treatment of wool and wool-rich blends: A study of bath composition

Elif Kaynak,Adem Mutlu,Ali Savaş Koparal,Mustafa Erdem Üreyen

doi:10.1177/1558925020922214

Abstract

Wool and wool-polyamide blended yarns (88.6% wool–11.4% polyamide 6,6 and 78.5% wool–21.5% polyamide 6,6) were knitted and the produced fabrics were treated by exhaustion method with zirconium complexes. Six different baths containing potassium hexafluorozirconate and zirconium acetate were studied. The flammability hazard was evaluated considering parameters such as the spread of flame, the heat release and the smoke release rate. Regardless of the blend composition, the untreated fabrics could not pass the vertical flammability test. 100% wool fabric could pass the vertical flammability test when treated with only 1% potassium hexafluorozirconate and 10% zirconium acetate solution. Higher compositions of metal complexes were required for the blended fabrics to pass the vertical flammability test. In the cone calorimeter test, 100% wool treated with 5% potassium hexafluorozirconate and 10% zirconium acetate solution gave the lowest peak heat release and smoke release rate values as 146.4 kW/m2 and 1.2 s−1, respectively.

Highlights

Wool and blends of wool have been traditionally used in aircraft upholstery where fire safety is a major technical challenge.[1,2,3] Wool exhibits relatively low flammability, upon heating it tends to form an expanded char which acts as a thermal barrier and protects the fabric from further damage.[4]
This study aims at investigating the effect of FR bath composition of both Zirpro and low smoke treatments on the flammability of wool furnishing fabrics
The higher percentage weight gain values were obtained for samples treated in baths containing potassium hexafluorozirconate, zirconium acetate and citric acid as the complexing agent, possibly due to the exhaustion of higher molecular weight zirconium citrate complexes onto wool

Summary

Introduction

Wool and blends of wool have been traditionally used in aircraft upholstery where fire safety is a major technical challenge.[1,2,3] Wool exhibits relatively low flammability, upon heating it tends to form an expanded char which acts as a thermal barrier and protects the fabric from further damage.[4]. Excessive stiffness and discoloration of fabrics were reported as the major drawbacks of THPC treatment.[7] The so-called Zirpro process which was developed back in 1960s has gained industrial importance since for the FR treatment of wool fabrics.

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