Abstract
Strongly alkaline electrolyzed water (SAEW) was prepared by electrolysis of tap water in a laboratory-made water electrolyzer. The pH of stored SAEW was stable for more than one month. The hardness of the electrolyzed water was 30% lower and the Na+ concentration was 18% higher than those of the tap water. Silkworm cocoon shells were boiled in pH 11.50 SAEW at a ratio of 1∶40∼80 (W/V) for 20 min and the sericin layers around the silk fibroin fibers were removed completely. The tensile properties and thermal decomposition temperature of a single filament of silk fibroin obtained by the SAEW method were almost the same as those for the fiber obtained by the neutral soap, and much higher than those for the fiber obtained by Na2CO3 degumming. The results demonstrate that SAEW is an environmentally friendly and pollution-free silk degumming agent that allows highly efficient, low cost recovery of sericin.
Highlights
A natural polymer of protein fibers produced by the silkworm Bombyx mori, is composed of 65,75% fibroin, 20,30% sericin and the remainder (,5%) is composed of wax, pigments, sugars and other impurities
The silkworm cocoon is composed of fibroin, a crystalline protein fiber, surrounded by layers of the protein sericin, which reinforces the cocoon structure
This is equivalent to 0.7995 g of ions present in 28 L of tap water precipitated in Strongly alkaline electrolyzed water (SAEW); 28.55 mg/L salt ions were precipitated from tap water by electrolysis
Summary
A natural polymer of protein fibers produced by the silkworm Bombyx mori, is composed of 65,75% fibroin, 20,30% sericin and the remainder (,5%) is composed of wax, pigments, sugars and other impurities. A decade ago, Kitagawa reported that acidic or alkaline electrolyzed water can be used for degumming B. mori cocoon silk [25]. Kim et al used 0.2% (W/V) sodium carbonate as the electrolyte to prepare pH 11.6 alkaline electrolyzed water for silk degumming and sericin recovery [27]. Hasegawa et al added crystalline clay mineral salts as an electrolyte into water and the resulting pH 12.0 alkaline electrolyzed water was used for the degumming of modified silk fiber and fabrics and sericin recycling [28]. Apart from the patent applications mentioned above, there is no report of the use of SAEW as a degumming/scouring agent for silk floss, silk spinning or the production of raw silk fabrics or effects on the mechanical properties of the fiber
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