Mohammad Gias Uddin

The exfoliation of silk fiber is an attractive method to produce silk micro and nano fibers that retain the secondary structure of native silk. However, most fibrillation methods used to date require the use of toxic and/or expensive solvents and the use of high energy. This study describes a low cost, scalable method to produce microfibrillated silk nanofibers without the use of toxic chemicals by controlling the application of shear using commercially scalable milling and homogenization equipment. Manipulation of the degumming conditions (alkaline concentration and degumming temperature) and the shear in milling and/or homogenization enabled control over the degree of fibrillation. The microfibrillated silk was then characterized to determine structural change during processing and the stability of the resulting suspensions at different pH. Silk nanofibers obtained from milling degummed silk were characterized using atomic force microscopy. Nanofibers obtained both with and without high pressure homogenization were then used to produce silk “protein paper” through casting. Silk degumming conditions played a critical role in determining the degree of microfibrillation and the properties of the cast silk papers. The silk papers produced from homogenized nanofibers showed excellent mechanical properties, high water absorption and wicking properties. The silk papers were excellent for supporting the attachment and growth of human skin keratinocytes, demonstrating application possibilities in healthcare such as wound healing.

The effect of biopolishing treatment on color yield of cotton is of great importance to the dyers. Such treatment using cellulase has an influential role on dye ability of the fabric. Research into this area of dyeing has yielded apparently contradictory results. Cellulase treatment prior to dyeing can facilitate the dyeing process resulting in the higher color yield. However, zero impact or negative influence on the color yield of dyed fabric has also been reported. On the other hand, cellulase treatment after dyeing can be retarded by the presence of dye molecules or due to the interaction between dye molecules and cellulose. Though lots of research works have been done on bio polishing and as the application of the process in the textile industry has increased to a greater extent, the information on the effects of this process on color yield, both in cases of cellulase pre-treatment and posttreatment are absolutely necessary. Considering this the paper mainly focuses the previous works regarding the effects of cellulase action (Both before and after dyeing) on the color yield of dyed cotton.

Some common problems of textile dyeing industries include uneven or faulty dyeing and formation of color patches on the fabric surface during dyeing and downstream processing of textiles materials. Such problems in the finished quality of fabric are generally tackled through a chemical stripping process which is a common practice in dyeing industries for the deep shade batches. However, reactive dyes cannot be stripped satisfactorily from cellulosic materials due to the formation of co-valent bonds between dye and fiber. This research was undertaken using 2.5% and 5% bi-hetero reactive dyes on pretreated cotton fabric and dye stripping was carried out in alkali reductive stripping process. The aim of the work was to investigate the effects of dye stripping on the quality of cotton fabric. Strength loss, weight loss, pilling resistance and absorbency of stripped fabric were calculated. Though with the increase of concentration of stripping chemicals and temperature, stripping percentages were improved; processing damage to the fabric such as losses in strength, weight and pilling resistance ratings was found. In contrast, increased fabric absorbency was found due to stripping. This is explained that during stripping, alkaline solution as an intracrystalline swelling agent is effective in loosening the crystalline region of cotton in addition to the amorphous region. Stripping agent can also attack such crystalline region. As a result, cotton fiber can release maximum number of hydroxyl groups which previously formed covalent bonds. This is the reason behind the stripped fabric having more water absorbency.