Unit 2 - Lecture 6 Topic 1

Question 1

How are natural cellulosic fibres classified?

Answer 1

They are classified according to the plant from which the fibres are removed. Ie. Seed hair, stem, leaf, and miscellaneous (root, bark, husk, moss).

Question 2

What do seed hair fibres do?

Answer 2

Cushion and protect seeds ie. cotton.

Question 3

What do bast fibres do?

Answer 3

Strengthen the stem of a plant ie. flax or linen.

Question 4

What do leaf fibres do?

Answer 4

Allow for pliability of leaves, ie. sisal.

Question 5

Cellulosic Fibre Properties:

Answer 5

High absorbency, heat conductivity, withstanding of high temperatures, low resiliency, good compressibility, electrical conductivity, dense fibres, sensitive to mineral acids but resisting of organic acids, prone to mildew attack, moth resistant, cricket and silverfish attracting, flammable, and moderately resistant to sunlight.

Question 6

Cellulose:

Answer 6

All cellulose fibres contain carbon, hydrogen and oxygen. The basic monomer of cellulose is where two glucose units repeat thousands of times.

Question 7

How are different cellulose properties determined?

Answer 7

The shape of the cellulose molecule, polarity, and affinity for water determine the fibre properties.

Question 8

What is the shape of cellulose?

Answer 8

Cellulose is a flat, thin, and long molecule that can pack into organized crystalline regions.

Question 9

What is the polarity of cellulose?

Answer 9

Each glucose ring has hydroxyl groups (-OH) which makes the molecule polar. Hydrogen bonds form between molecules, leading to the fabric’s high absorbency.

Question 10

How does cellulose like (or not like) water?

Answer 10

Because it is a polar molecule, cellulose forms H bonds with water, making it extremely absorbent.

Question 11

Hydroxyl Groups on Cellulose:

Answer 11

React with water, dyes, and finishes .