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Abstract
Silk fibre consists of two proteinous filaments known as fibroin (70%) which are cemented together and enveloped by silk proteinous glue called sericin (20- 30%). The sericin of silk gum is insoluble in water and it cannot be removed from raw silk by mere washing treatement. Therefore, the insoluble sericin has to be converted to soluble form. The process of slubilizing and removal of sericin from silk in called degumming. Degumming have the following adventages: i) improve the harsh and stiff feeling of raw silk to smooth and soft feeling, ii) improve the lustre and increase the whiteness of silk fabric, iii) facilitate the dye penetration to degummed silk fabric.
The present work focuses on: i) comparing the degumming action of conventional degumming agents versus enzymatic degumming as an eco-friendly, mild treatment, ii) finding out the proper conditions for attaining better performance properties as well as, iii) evaluating the impact of degumming step on the extent of post-dyeing with anionic dyes.
Given below are a summary and conclusions arrived from these studies.
1. Increasing succinic acid concentration up to 6 g/l results in a remarkable improvement in the extent of degumming of silk yarn.
2. The extent of degumming is determined by the type of silk substrate and follows the descending order: Silk yarn >> Raw silk fabric.
3. The extent of degumming increased considerably after the acid treatment.
4. Increasing the used anionic surfactant concentration from zero up to 2.5 g/l brings about an improvement in the extent of degumming at 100°C for 60 min. at LR I/30, regardless of the used substrate.
5. Degumming loss of treated silk yarns increased sharply, from 4.05 % up to 17.0 %, as the amount of the surfactant increased.
6. Increasing the nonionic surfactant concentration up to 2.5 g/l brings about a noticeable increase in the degumming loss of the treated raw silk fabric.
7. Increasing Protex® enzyme concentration up to 1 g/l results in a remarkable increase in the weight loss of silk yarn as well as in the weight loss of silk fabric.
8. Increasing Alkalase enzyme concentration up to 1 g/l brings about a dramatic increase in the extent of degumming.
9. The extent of degumming is determined by the nature of the enzyme, i.e. Alkalase > Protex” Multiplus L>> None.
10. Prolonging the treatment time has a positive impact on the extent of degumming.
11.Raising the treatment temperature from 80°C up to 100°C for 60 min. results in a significant improvement in the extent of
12. pH 10 acts in favor of enhancing the performance and catalytic activity of the used enzymes.
13.Increasing LR up to 1/40 is accompanied by a slight improvement in the degumming efficiency, irrespective of the used enzyme.
14.The degumming loss is determined by the kind of
degumming agent and follow the decreasing order: Alkalase enzyme > Protex® enzyme > Monochloroacetic acid ≈ Succinic acid ≈ Nonionic surfactant.,
15.As the weight loss increased the degummed fabric samples become softer and thus fabric stiffness decreased.
16. The K/S values of such dyeings are better with than without degumming.
17. The K/S as well as fastness properties of the obtained dyeing are determined by the nature of the anionic dye stuff.