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2 Autex Research Journal

2 2005

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Studies on structure and properties of nephila-spider silk dragline

100%

Rengasamy R. S. , Jassal M. , Rameshkumar C.

tom Vol. 5, no. 1

30--39

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.

The tensile behaviour of spider silk

100%

Van Nimmen E. , Gellynck K. , Van Langenhove L.

tom Vol. 5, no. 3

120--126

Spider silk has attracted the interest of several researchers in recent years because it displays a unique combination of high tensile strength, high breaking strain and an ultra-low weight. Hitherto, the focus has always been on dragline and viscid silk, whereas research on spider cocoon silk is limited. In order to explain the structure-property relationship of spider silk, the stress-strain behaviour of cocoon and dragline silk is compared in this study. It is shown that both fibres have completely different stress-strain behaviours.In addition, the influence of the testing speed is investigated. For cocoon silk, lower testing speeds result in lower strength, stiffness and higher post-modulus. When the stress-strain curve is simulated by an extended Maxwell model, as testing speed increases, the level of the hardening region is higher, the yield region moves to higher strains and the hardening region in the stress-strain curve becomes more horizontal. However, a speed of 20 mm/min can be considered as a saturation point where the effect of the speed decreases. The influence of the testing speed on dragline silk is clearly less pronounced than for cocoon silk. However, a more detailed study of the stress-strain curves of dragline revealed different possible shapes for the stress-strain behaviour of dragline silk.