The evaluation of hydrogen peroxide bleaching of <i>Gonometa postica</i> silk

Abstract

The effect of hydrogen peroxide bleaching on Gonometa postica silk and the influence that temperature, pH and time duration had on hydrogen peroxide release , colour change, breaking load and stiffness were determined.

The best bleaching (81 delta E) of the Gonometa postica silk fabric was obtained with 60 minutes exposure to hydrogen peroxide at 90°C and pH 8. Bleaching lowered the strength of the Gonometa postica silk fabric 7, 6% at pH10 but 12, 8% at pH 8. Rigidity of Gonometa postica silk fabric increased as a result of bleaching at 60°C, 70°C and 90°C at pH 8 and pH 10. The bending length was the highest (5.28 cm) after bleaching at 90°C and pH 8.

Although acceptable bleaching of Gonometa postica silk fabric is reached with 60 minute exposure to hydrogen peroxide at 90°C and pH 8 or 180 minutes at 70°C at pH 8, bleaching cannot be recommended because the fabric becomes too rigid and requires a lower load to break. Gonometa postica silk fabric should be used in its natural colour or dyed in darker colours until a bleaching practice that would not cause the fabric to be harsh and stiff is developed.