Difference between Wool and Silk Fiber

Wool fiber: 
Wool is the natural highly crimped textile fiber obtained from sheep and other animals. Wool is the first fibers to be spun into yarn and into fabric. It’s surface consists of a series of serrated scales, which overlap each other like as scales of fish. It has a higher ignition threshold than many other fibers and is flame retardant up to 600 degree Celsius.

Silk fiber:

Silk is a natural protein fiber produced from the silk worm. It is only one continuous filament fiber among the natural fiber. It is also the most beautiful textile fiber. So, silk is called queen of fiber. 

Wool and silk fiber
Fig: Wool and silk fiber
Distinguish between Wool and Silk Fiber:
Wool is produced from fur of animals.
Silk is produced from cocoons of silkworms.
Outer Surface
Uneven scale
Very smooth, regular and fine
It is a staple fiber and is fuzzy and length is 2-8 cm
It is usually a filament and is smooth and length is 300-2000 meter
It has more amorphous areas and more absorbent.
It is very crystalline and is less absorbent.
It is more elastic and resilient.
It is less elastic and resilient.
Wool doesn’t have a shine.
Silk has a shiny, shimmery appearance.

10 µm to 20 µm
Wool keratin polymer is a helical configuration crosslink polymer.
The silk fibron polymer is a linear fibroin polymer.
Amino acid
Wool polymer is composed of twenty different amino acids.
 Silk is polymer is composed of sixteen different amino acids.
Disulphide bond
Wool contain disulphide bonds i.e. cystine.
Silk does not contain any disulphide bonds.
Polymer length
Wool polymer is shorter than the silk polymer.
Silk polymer is about as long as 140 nm.
Effect of acids
It is degraded less than silk.
It is degraded more than wool because of absence of disulphide bonds, perspiration which is acidic will cause breakdown of silk polymer.
Dimensional stability

It has four parts in its fiber structure and therefore shrinks and felts.
It is a solid fiber.
Repeating unit
Repeating unit of wool is the Peptide Bond.
Repeating unit of silk is also the Peptide Bond.
Chemical bond
Chemical bonding groupings of the wool polymer are hydrogen bonds, salt linkages, peptide and disulfide bonds etc.
Chemical bonding groupings of the silk polymer are hydrogen bonds, the carboxyl and amino groups which give rise to the salt linkages.
Attraction of polymer
Attraction between wool polymers are thought to be hydrogen bonds and Van der wall forces.
Attraction between silk polymers are thought to be hydrogen bonds.
Polymer arrangement
Keratin polymer lies in cross-linked and helical pattern.
Fibroin polymers must therefore lie closer together than this less than 0.5 nm.
Amorphous structure
Crystal structure
Hydroscopic nature

It is more absorbent.
Since it has a very crystalline polymer system, it is less absorbent than wool.
Resistant to abrasion
Resistant to sun light
Wool has good resistant against sun light.
Continuous exposure to light weakens silk faster than cotton or wool.
Thermal properties

It is less sensitive to heat.
It is more sensitive to heat.
Wool is specially used for winter clothing.
Silk is often used for formal dresses.