Natural silks

This includes organic fibrous materials on a cellulose base such as paper, pressboard, cotton, cotton cloth and natural silk etc., impregnated with lacquers or immersed in an insulating liquid. The impregnation or immersion ensures that the oxygen content of the air does not affect... 

Bolting cloth (silk) Screens woven of twisted multifilament natural silk. 

In semi-cristalline polymers, rate-enhancement under stress has been frequently observed, e.g. in UV-photooxidation of Kapron, natural silk [80], polycaprolactam and polyethylene terephthalate [81]. Quantitative interpretation is, however, difficult in these systems although the overall rate is determined by the level of applied stress, other stress-dependent factors like the rate of oxygen diffusion or change in polymer morphology could occur concurrently and supersede the elementary molecular steps [82, 83], Similar experiments in the fluid state showed unequivocally that flow-induced stresses can accelerate several types of reactions, the best studied being the hydrolysis of DNA [84] and of polyacrylamide [85]. In these examples, hydrolysis involves breaking of the ester O —PO and the amide N —CO bonds. The tensile stress stretches the chain, and therefore, facilitates the... 

Catalytic asymmetric hydrogenation is a relatively developed process compared to other asymmetric processes practised today. Efforts in this direction have already been made. The first report in this respect is the use of Pd on natural silk for hydrogenating oximes and oxazolones with optical yields of about 36%. Izumi and Sachtler have shown that a Ni catalyst modified with (i ,.R)-tartaric acid can be used for the hydrogenation of methylacetoacetate to methyl-3-hydroxybutyrate. The group of Orito in Japan (1979) and Blaser and co-workers at Ciba-Geigy (1988) have reported the use of a cinchona alkaloid modified Pt/AlaO.i catalyst for the enantioselective hydrogenation of a-keto-esters such as methylpyruvate and ethylpyruvate to optically active (/f)-methylacetate and (7 )-ethylacetate. 

Braun, F. N., andViney, C. (2003). Modelling self assembly of natural silk solutions. Int.J. Biol. Macromol. 32, 59—65. 

Kerkam, K., Viney, C., Kaplan, D., and Lombardi, S. (1991). Liquid crystallinity of natural silk secretions. Nature 349, 596-598. 

Viney, C. (1997). Natural silks Archetypal supramolecular assembly of polymer fibres. Supramol. Sci. 4, 75—81. 

Hybrid polymers containing peptide blocks were also reported to mimic the /3-sheet stmctures in natural silk (Winningham and Sogah 1997 Qu et al. 2000 Rathore and Sogah 2001). 

Natural Silks. Many lepidopterous insects secrete from special glands a liquid which becomes solid in the air in the form of filaments destined for the construction of the cocoons in which the insects pass one stage of their existence. Ordinary silk is derived from Bombyx mori, and wild silk from other insects (Antheraea myliUa, A. Yama-mai), which live wild particularly in India, China and Japan. 

A portion of the sample is immersed in the cold in concentrated hydrochloric acid or in sulphuric acid of 58° Baumd ordinary non-weighted, natural silk dissolves readily, heavily weighted silk and wild natural silk more slowly artificial silks dissolve after some time, those with a gelatine basis first softening and then dissolving in about two hours. 

Mixed cotton, wool and natural silk fabric. 

Mixed fabrics containing natural silk and artificial silk based on either cellulose, or nitrocellulose or viscose. 

Where natural and artificial silks are present together, use is made of the property exhibited by 10% caustic potash solution and by Ldwe s solution, in the conditions already mentioned, of dissolving natural silk and leaving artificial silk undissolved. 

A. Mixed fabric containing cotton, wool, natural silk and artificial cellulose, nitrocellulose or viscose silk. 

If this shortened method is employed, the following rules must be followed in cotton and wool fabrics, the cotton is determined for preference as in case 1 (6) and the wool calculated by difference. In cotton and silk or wool and silk fabrics, the silk is determined for preference in the manner described in case 2 (c) and the other component calculated by difference. In cotton, wool and natural silk fabrics, the silk (2,c) and cotton (1,6) are determined for preference and the wool calculated. 

Metallisation of fibres is not only a physical process determined by absorption capacity of the fibres for the metal and diffusion capacity of the metal in the fibre structure, but also depends on chemical parameters such as chemical structure of the fibres, presence of functional groups, reactivity of the fibre and the metal, oxidation state of the metal and the presence, necessity and reactivity of supporting chemicals (e.g. reducing agent). Therefore, it was necessary first to study metallisation at different types of fibres in order to investigate which structure is most useful for further research. In this respect, viscose, cotton, natural silk and polyacrylonitrile fibres were investigated because of their different structure and properties and their availability in the New Independent States of the former Soviet Union (Uzbekistan, Kazakhstan, Kyrgyzstan). 

The results of this analysis are shown in Table 11.1. It is clear that absorption of nickel in all fibres is reasonably high, but the amount of metallic nickel is considerably higher in PAN fibres and, to a lesser extent, in natural silk. This indicates that the structure of the fibres (pore size and permeability as well as functional groups) plays an important role. Sodium dithionite and rongalite are known as good reducing agents, but their stability is fairly limited. One of their decomposition products (particularly in acidic solutions) is sulphide, which explains why an important fraction of... 

Because natural silk, as a protein fiber of animal origin, resembles wool in its chemical structure, it can be dyed with most of the classes of dyes used for wool. The choice of dyes depends essentially on the fastness properties required. 

Of great importance for the dyeing of natural silk are selected members of the class of acid wool dyes (see above). The occasionally inadequate wetfastness of these dyeings can be substantially improved by the proper aftertreatment (e.g., with potassium sodium tartrate and tannin). 

Paul van der Schoot, Nucleation and Co-Operativity in Supramolecular Polymers Michael J. McPherson, Kier James, Stuart Kyle, Stephen Parsons, and Jessica Riley, Recombinant Production of Self-Assembling Peptides Boxun Leng, Lei Huang, and Zhengzhong Shao, Inspiration from Natural Silks and Their Proteins Sally L. Gras, Surface- and Solution-Based Assembly of Amyloid Fibrils for Biomedical and Nanotechnology Applications... 

Boxun Leng, Lei Huang, and Zhengzhong Shao, Inspiration from Natural Silks and Their Proteins... 

Result The warp and filling threads are composed of natural silk, grounde with the lichen dye orchil (C.I.Natural Red 28) and dyed with madder (Rubia tintorum). 

Inspiration from Natural Silks and Their Proteins... 

In view of the various level of structural organization, it is worthwhile to draw a comparison between natural silk fibers (silkworm silk and spider silk) and man-made silk-based materials. 

The properties of natural silk are affected by numerous factors, such as nutrition, temperature, hydration state, extension rate, reeling speed (ICnight et al., 2000 Madsen et al., 1999 Riekel et al., 1999 Vollrath and ICnight, 1999 Vollrath et al., 2001), and spinning medium during the manufacture (Chen et al.,... 

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