Mechanical Properties of Silk Yarn Degummed with Several Proteases

Abstract

The silk filament spun by the silkworm (Bombyx mori) is composed of two fibroin filaments held together by a cementing layer of sericin. Fibroin and sericin account for about 75 wt% and 25 wt% of the raw silk, respectively. The degumming process consists in removing the sericin layer prior to dyeing using a solution of soap, synthetic detergents, or proteolytic enzymes. Silk yarn was degummed with different commercially available enzymes, two alkaline, a neutral, and an acidic proteases and the results were compared in terms of physical and mechanical properties. Proteases were used under optimum conditions of pH and temperature. The treatments were carried out with three different enzyme dosages, that is, 0.2, 1, and 5 U/g yarn. Soap was taken as the standard method of degumming and enzymatic treatments were compared with this method. The degree of polymerization of silk fibroin was assessed by measuring the intrinsic viscosity of the treated samples.

Key Words:

• Silk yarn
• sericin
• silk degumming
• mechanical properties
• intrinsic viscosity