Page 208 - Handbook of Properties of Textile and Technical Fibres

Engineering properties of spider 6

silk

Frank K. Ko, Lynn Y. Wan
University of British Columbia, Vancouver, Canada

6.1 Introduction

In spite of the progress made in recent years in polymeric fiber science and technolo-
gies, the search for a truly strong and tough fiber continues. Most manmade fibers
exhibit either high tensile strength and stiffness or low strength and high extensibility.
Therefore strength and toughness are usually considered mutually exclusive properties
for materials. The answer may be found from spider silk that has long been recognized
as the wonder fiber for its unique combination of high strength and rupture elongation.
The excellent combination of strength and toughness of the silk from Nephila clavipes
has long been by the South Sea Islanders who use the silk to make various kinds of
bags and fishing nets (Levi et al., 1968). The strength of spider dragline silk is approx-
imately 4 GPa that is comparable to one of the high-performance synthetic fibresd
Kevlar. The elongation at break of dragline silk is up to 35%, which is much higher
5
than that of Kevlar (merely 5%). The energy to break can reach 1 10 J/kg in
4
dragline silk, more than three times that of Kevlar (3 10 J/kg) and other industrial
fibers (Rising et al., 2005).
Considering the remarkable mechanochemical properties of spider silk and fueled
by the recent progress in biotechnology, there is a revival of interest in using spider silk
as a model for the engineering of high-energy absorption fibers (Kaplan et al., 1994).
In order to obtain realistic blue prints for ideal strong and high-energy absorption fibers
there is a need for a thorough understanding of the structure of dragline silk and precise
characterization of the engineering properties of spider silk.
There is a wealth of information on the biochemical and behavioral aspects of
orb weaver spiders, which can be found in the book by Witt et al. (2012).Studies
on the fine structure, chemical composition, synthesis, and silk spinning have
already been reported in 1960s by Friedrick (Friedric and Langer, 1969), Peakall
(Peakall, 1964, 1969), Lucas (Lucas et al., 1960), Warwicker (Warwicker, 1960),
Levi (Levi et al., 1968), Zemlin (Zemlin, 1968), Marples (Marples, 1967), Wilson
(Wilson, 1962a,b, 1969) and more recently by Vollrath et al. (Vollrath et al., 1998;
Knight and Vollrath, 1999, 2002; Vollrath and Knight, 1999, 2001; Vollrath, 2000;
Shao et al., 2003; Liu et al., 2005a; Vollrath and Porter, 2006; David and Fritz,
2009). The morphology and molecular structure of spider silk have been widely
investigated by microscopy, polarized light microscopy (Gosline et al., 1986;
Blackledge et al., 2005), scanning electron microscopy (Vollrath et al., 1996),
atomic force microscopy (Li et al., 1994; Slotta et al., 2007), X-ray diffraction

Handbook of Properties of Textile and Technical Fibres. https://doi.org/10.1016/B978-0-08-101272-7.00006-7
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