13 - Silk from silkworms and spiders as high-performance fibers

Abstract

Silks are of interest for their remarkable mechanical properties as well as their durability, luster, and feel. Silk fibers generated by spiders and silkworms represent the strongest natural fibers known, even rivaling synthetic high-performance fibers in terms of mechanical properties. Silk is spun by animals for various reasons, but mostly for the strength that their silk provides. Numerous silk-spinning animals like caterpillars, silkworms, and spiders exist in nature, but spider silk is the strongest of them all. The high tensile strength of spider silk rivals that of high-grade steel and aramid fibers such as Kevlar. Spider silk is also lighter than steel and elongates more than aramid. Thus spider silk seems to be the perfect candidate to replace synthetic fibers. Bombyx mori silkworm silk possesses the highest tensile strength after spider silk; silk harvesting from this highly domesticated silkworm is an easier alternative for high-performance applications. Silk fibers from spiders and silkworms could prove an effective and novel reinforcement in biocomposites. Considering the increasing renewed interest in engineering materials of natural origin, silks seem to be a strong natural fiber candidate for reinforcements in polymer composites. Silk fiber reinforcements have another benefit over plant fibers in that they can withstand bending without breaking more so than plant fibers can, improving the mechanical performance of the composite. Consequently, silk fiber reinforcements offer a unique opportunity in the production of high fiber volume fraction natural fiber composites. Not only would silk-reinforced composites be more sustainable because less energy is required to produce the fibers, but less environmentally unfriendly polymer filler would be needed. Ultimately, these composites could offer better mechanical performance too, particularly where light weight and high toughness are required, as well as sustainability. In this chapter, a detailed description of different varieties of silkworm silks and their structure, properties, and high performance applications are presented. In addition, the importance of spider silks and their characteristics and applications in the production of biocomposites and other high-performance applications are also presented.