Question

Why silk is a strong fibre?

Answer 1

Silk is extremely strong— the strongest natural fiber known to man, one filament of silk is stronger then a comparable filament of steel!
Silk is the strongest natural fiber and is very strong in terms of tensile strength, meaning it can withstand a lot of pulling type pressure without breaking.

Inorder to understand why silk is strong,we need to go to melecular level.
Silk emitted by the silkworm consists of two main proteins, sericin and fibroin.
Fibroin is made up of the amino acids.Since amino acid molecule forms chains with different molecules,the structure of silk is like a network.
Hydrogen bonds form between chains, and side chains form above and below the plane of the hydrogen bond network.Since hydrogen bonds are one of the strongest chemical bond,this make the silk structure more strong to tensile force.
This tensile strength is due to the many interceded hydrogen bonds, and when stretched the force is applied to these numerous bonds and they do not break.