Unit 2 - Lecture 9 Topic 1

Question 1

Sericulture:

Answer 1

The production of cultivated silk created by the silk moth, Bombyx mori which feeds on mulberry leaves. When its larvae spin cocoons to pupate, their silk is harvested from the cocoon.

Question 2

Fibroin:

Answer 2

The strands of silk extruding from silkworms.

Question 3

Sericin:

Answer 3

A water-soluble protein that coats silk. This is removed in the cultivation process through ‘degumming.’

Question 4

Reeling:

Answer 4

The unrolling of silk cocoons.

Question 5

Throwing:

Answer 5

The making of silk yarns.

Question 6

Raw silk composure:

Answer 6

Two filaments adhered together
with sericin.

Question 7

Degummed:

Answer 7

Silk is cultivated through ‘degumming, ‘ which removes sericin and separates the raw filament.

Question 8

Wild and Tussah Silk:

Answer 8

Most wild silk is in staple form, but Tussah can be found in filament form.

Question 9

Dupioni Silk:

Answer 9

When two cultivated silkworms spin their cocoons together.

Question 10

Weighted Silk:

Answer 10

The addition of metallic salts onto silk.

Question 11

What is the length of silk?

Answer 11

Silk is the only natural filament fibre with around 900 metres of usable silk filament per
cocoon.

Question 12

What is the diameter of silk?

Answer 12

Silk has a fine diameter (12-30 μm) that is uneven along the length.

Question 13

What are the colour properties of silk?

Answer 13

Cultivated silk is translucent and white while wild silk tends to be tan.

Question 14

What is the shape and contour of cultivated silk?

Answer 14

Cultivated silk has a triangular cross-section with rounded corners and a smooth longitudinal surface.

Question 15

What is the shape and contour of Tussah silk?

Answer 15

Tussah silk is wedge-shaped in cross-section with ribbon-like striations along the length.

Question 16

What is the microstructure of cultivated silk?

Answer 16

There is no discernable microstructure. Cultivated silk is simply a fine, coagulated stream of protein polymer solution.

Question 17

What is the microstructure of wild and tussah silk?

Answer 17

This type of silk has an internal fibrillar structure, but it is not as complex as cotton or wool.

Question 18

Fibroin:

Answer 18

The protein in silk. It is made from 15-18 different amino acids. Silk doesn’t have cystine as no disulphide linkages are present in silk.

Question 19

What are the four main types of amino acids present in silk?

Answer 19

Glycine (H), alanine (CH3), serine (CH2 + OH), and Tyrosine (CH2 + Benzene + OH). These first three amino acids make up around 86% of the fibre. They are small and not bulky.

Question 20

Is silk crystalline?

Answer 20

Silk is a highly crystalline fibre: 60-70% crystalline and 30-40% amorphous.

Question 21

How are molecules arranged in silk?

Answer 21

Silk molecules are arranged in a parallel, sheet-like configuration. The silk polypeptide chains are fully extended in a beta (β)-sheet conformation.

Question 22

What intermolecular forces are present in silk?

Answer 22

Silk has hydrogen bonding, van der Waals, and some ionic bonding.

Question 23

Is silk polymerized?

Answer 23

Silk has a high degree of polymerization.

Question 24

Is silk orientated?

Answer 24

Silk has a high orientation.

Question 25

How would you expect wool and silk to compare for strength based on their structures?

Answer 25

Silk is stronger than wool because silk is more crystalline and has greater orientation.

Question 26

How would you expect wool and silk to compare for moisture absorbency based on their structures?

Answer 26

Silk is less absorbent than wool because silk is more crystalline.

Question 27

How would you expect wool and silk to compare for resiliency based on their structures?

Answer 27

Silk is less resilient than wool because the sheet-like polymer arrangement is already fully extended, and wool has disulphide bonds that take wool back to its original position.