Silver nanoparticles were produced by a chemical reduction method that reduced silver nitrate with reducing agents such as hydrazine and glucose. The silver nanoparticles were characterized with transmission electron microscope, scanning electron microscope, and optical microscope. The effects of process parameters such as the stirring speed, temperature, type of reducing agent, and dispersing agent on the particle size were studied. The particle size decreased with an increase in the stirring speed and a decrease in the process temperature. Smaller particles were formed when the silver nitrate was reduced by glucose versus those that were formed by reduction with hydrazine. Silver nanoparticles with average sizes of 10 and 35 nm, produced by reduction with hydrazine at 5 and 408C, were applied to silk by an exhaust method. Silk fabrics treated with 40 ppm silver hydrosol produced at 58C and 60 ppm silver hydrosol produced at 408C showed 100% antimicrobial activity against the gram-positive bacterium Staphylococcus aureus. The durability of the antimicrobial property of the treated silk fabric to washing was also examined and is presented.

Degumming of silk involves the cleavage of peptide bonds of sericin, either by hydrolytic or enzymatic methods, and the subsequent removal of sericin from the silk fibroin. Hydrolysis of sericin can be carried out under neutral, alkaline or acidic conditions to give four fractions, each having different properties. Boiling‐off in alkaline soap solution is the most popular degumming method. There are many qualitative methods of assessing the extent of degumming; however, quantitative methods have yet to be developed. Degumming can be carried out on yarn or fabric, in manually or mechanically operated machines. Mechanisms of degumming remain to be investigated.

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Sericin powder was prepared from a boiled solution of silk cocoons through salting-out with ammonium sulfate. The obtained sericin powder was characterized with Fourier transform infrared (FTIR), X-ray, ultraviolet (UV) absorption, and nitrogen content measurements. The aqueous sericin solution was applied onto the polyester fabric (pretreated with NaOH) along with glutaraldehyde as a crosslinking agent with a pad-dry-cure method. The processing conditions of the crosslinking agent were optimized. The presence of sericin was confirmed by the estimation of the nitrogen content and amino groups on the treated fabric. The dyeability of the treated fabric with acid and reactive dyes was studied. The performance properties, such as the moisture content, UV absorption, antistatic, crease recovery, and bending length, of the treated fabric were tested. The FTIR, X-ray, UV absorption, and nitrogen content results confirmed the purity of the sericin powder obtained with the salting-out method. The amino acid content, nitrogen content, and Kubelka Monk function (K/S) values of the sericin-treated fabric increased with an increase in the concentration of sericin in the padding liquor. The K/S value of the dyed samples was found to be linearly correlated with the number of amino groups present on the samples. There was a noticeable improvement in the moisture content and antistatic and UV absorption properties of the sericin-treated fabrics.

This article describes the recovery of silk sericin from three different degumming liquors, that is, high temperature high pressure (HTHP), alkaline, and soap plus alkali (SPA), using membrane filtration technology. The recovery of sericin by membrane technology results in the reduction of about 78-85% chemical oxygen demand as well as biological oxygen demand values in the final discharge liquor. The sericin powders produced from the purified degumming liquors have been characterized in terms of color, nitrogen content, protein content, ash content, and thermogravimetric analysis and compared. It has been found that the sericin recovered from HTHP degumming liquor has about 98% protein content as compared to that recovered from alkaline (92%) and SPA (67%) degumming liquors. The molecular weight distribution and secondary structure of the recovered sericin powders have been determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and circular dichroism (CD) spectroscopy, respectively. The molecular weight range of sericin recovered from HTHP, alkaline, and SPA degumming liquor was 20->205 kDa, 20-97 kDa, and 20-43 kDa, respectively. The secondary structure of sericin recovered from HTHP degumming showed random coil conformation with some b sheet structure. The sericin recovered from alkaline and SPA degumming liquors showed denaturation with some random coil, b sheet, and a helix conformation. The functional properties of the three different recovered sericin powder samples in terms of moisture content and ultra protection factor (UPF) have also been evaluated and compared.