INSTERESTING FACTS ABOUT SPIDER SILK

• Spider silk is a remarkably strong material. Its tensile strength is comparable to that of high-grade steel (1500 MPa), and about half as strong as aramid filaments, such as Twaron or Kevlar (3000 MPa). Spider silk is about a fifth of the density of steel; a strand long enough to circle the Earth would weigh less than 500 grams (18 oz).

• Spider silk is also especially ductile, able to stretch up to 1.4 times its relaxed length without breaking; this gives it a very high toughness (or work to fracture), which "equals that of commercial polyaramid (aromatic nylon) filaments, which themselves are benchmarks of modern polymer fibre technology". It can hold its strength below −40 °C.

• The strongest known spider silk is produced by the species Darwin's bark spider (Caerostris darwini): "The toughness of forcibly silked fibers averages 350 MJ/m3, with some samples reaching 520 MJ/m3.... Thus, C. darwini silk is more than twice as tough as any previously described silk, and over 10 times stronger than Kevlar."

• It has been suggested that a Boeing 747 could be stopped in flight by a single pencil-width strand and spider silk is almost as strong as Kevlar, the toughest man-made polymer. 

Mechanical Properties:

Material Strength Elasticity Energy to Break (N/m2) (%) (J/kg)

Major Amp. Silk 4 E 9 35 1 E 5Minor Amp. Silk 1 E 9 5 3 E 4Flagelliform Silk 1 E 9 200+ 1 E 5Kevlar 4 E 9 5 3 E 4Rubber 1 E 1 600 8 E 4Tendon 1 E 9 5 5 E 3

Various biological and manmade materials are listed with their strength, elasticity, and energy to break. Note the over ten-fold increase in the energy to break of MaSp1 and Flagelliform silk compared to KEVLAR. This dramatic increase is due to the elasticity of these types of spider silk.