Polymers: Silk
A biomaterial, silk is a loosely defined material created by several different varieties of insects. The most common and well known form of silk is created by the Chinese silk moth (mulberry silkeworm, Bombyx mori) and is woven to create many different textiles.
As well as a biomaterial, silk can further be specified as a polymer, or biopolymer. It is mostly made up of proteins, the two main proteins of which are fibroin (the structural center) and sericin (the sticky material surrounding it). The proteins themselves are composed of a variety of amino acids: glycine, alanine, and serine make up over 80% of the amino acids in fibroin while glycine, serine, aspartic acid, glutamic acid, and threonine are the five main amino acids in sericin (just under 80% of the protein).
Natural silk (from the silkworm mentioned above) is an incredibly strong textile fiber, especially compared to other materials such as wool or the hair of other animals like alpacas or llamas. It is also stiffer and naturally crease-resistant. Less favorable properties of silk include the fact that it can loose its strength when wet, its (relatively) poor elasticity, and the fact that it is a poor conductor of electricity and therefore susceptible to static cling.
This form of silk has been used for thousands of years, easily dyed and with a soft texture. It was almost exclusively used for clothing and other textiles such as rugs or blankets and was once a symbol of wealth due to the labor and expense used to cultivate and weave the raw material. In modern times the uses of silk have expanded, including commercial uses such as parachutes or artillery gunpowder bags and medical uses such as surgical sutures or other applications that rely on its biocompatibility (current research suggests the sericin must be removed to ensure biocompatibility).
Sources/Further Reading: (1 - images 1 and 2) ( 2 ) (3 - image 3) (4 - image 4) ( 5 ) ( 6 )
