structural & physical properties of silk

structural & physical properties of silk - AUTEX...

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AUTEX Research Journal, Vol. 5, No1, March 2005 © AUTEX 30 STUDIES ON STRUCTURE AND PROPERTIES OF NEPHILA-SPIDER SILK DRAGLINE Raju Seenivasan Rengasamy, Manjeet Jassal and Chidambaram Rameshkumar Department of Textile Technology Indian Institute of Technology, Delhi-110 016 E-mail: . . Abstract Spider dragline silk is an extremely strong biopolymer and has unique combination of desirable mechanical properties. In the present paper dragline of Golden Nephila spider was studied for dimensional, structural, physical and tensile properties. The test results established significant variability in diameter and denier of dragline filaments. The filaments possessed nearly circular cross-section and were found to be sensitive to moisture. The draglines exhibited super contraction in water. It has high strength and large elongation to break (45.9 cN/tex and 38.7 %, respectively). X-ray crystallinity of 17.5 % was obtained. The fibres were also subjected to thermo- mechanical and dynamic mechanical analysis. Key words: Spider silk, Dragline, Golden Nephila, Characterization, Mechanical properties Introduction In the world of natural fibres, spider filament has been recognized as the wonder fibre for its unique combination of high strength and elongation at break. Unlike B.Mori silk, spider silk has not been domesticated for textile applications. This is due to the difficulty in raising dense population of spiders due to their solitary and predatory nature. In addition, orb webs are not reel able as a single fibre, unlike the fibroin from the cocoon of the silk worm. Furthermore, in comparison to the silkworm cocoon silk, spider generates only small quantities of silk and function as prey capture, reproduction, vibrational sensors, safety lines and dispersion tools [1]. The spiders produce wide range of silk fibres for many different purposes with surprisingly varied mechanical properties. However, the most outstanding properties are found in the dragline and radial threads of some giant spiders such as Nephila. Although they are not as strong as some synthetic fibres such as Kevlar, but it is more elastic. This allows it to absorb more energy prior to breaking than any commonly used synthetic material. These fibres combine the advantages of a protein structure, including hydrophilic properties, biodegradability, biocompatibility with high strength and high modulus, comparable to some synthetic high performance fibres but with an extremely high extension of break [2]. Sullivan [3] cited that the breaking stress of the dragline silk for three species of spiders range from 1420 to 1550 million N/m 2 with elongation at break ranging from 16 to 30%. Together these result in a specific toughness comparable to the best synthetic material. The breaking stress of Kevlar 49, high- tenacity nylon and Carbon fibers are 2000, 1600 and 1750 million N/m 2 , with the elongation at break of
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This note was uploaded on 01/27/2012 for the course ECOLOGY 300 taught by Professor Zumdahli during the Spring '11 term at St. Mary NE.

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structural & physical properties of silk - AUTEX...

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