The spider-‘silk’ produced by Spiderman about as thick as his arm — it’s more like ‘spider-rope’. But, does it really need to be that thick? No, says this SciAm article on the wonderful combination of mechanical properties of real spidersilk.
The different silks have unique physical properties such as strength, toughness and elasticity, but all are very strong compared to other natural and synthetic materials. … The movie Spider-Man drastically underestimates the strength of silk�real dragline silk would not need to be nearly as thick as the strands deployed by our web-swinging hero in the movie.
Here’s a quick description of what makes up one of the several forms of spidersilk:
Dragline silk is a composite material comprised of two different proteins, each containing three types of regions with distinct properties. One of these forms an amorphous (noncrystalline) matrix that is stretchable, giving the silk elasticity. When an insect strikes the web, the stretching of the matrix enables the web to absorb the kinetic energy of the insect�s flight. Embedded in the amorphous portions of both proteins are two kinds of crystalline regions that toughen the silk. Although both kinds of crystalline regions are tightly pleated and resist stretching, one of them is rigid. It is thought that the pleats of the less rigid crystalline regions not only fit into the pleats in the rigid crystals but that they also interact with the amorphous areas in the proteins, thus anchoring the rigid crystals to the matrix. The resulting composite is strong, tough, and yet elastic.