Unit 1 - Lecture 4 Topic 2

Question 1

Mechanical Properties of Fibres:

Answer 1

Strength, initial modulus, flexibility, elongation, elastic recovery, resiliency, and abrasion resistance.

Question 2

Fibre Strength:

Answer 2

The ability to resist breaking/rupture when pulling, tearing or bursting forces are applied. Tensile strength (tenacity) is the ability to withstand a pulling force which is related to fabric structure: A resistance to ripping is called tear strength but a resistance to rupture is called bursting strength.

Question 3

Initial Modulus:

Answer 3

Initial resistance to a tensile force, which is described as a measure of fibre stiffness. Low initial modulus means that the fibre is easy to bend or stretch.

Question 4

Describe low initial modulus:

Answer 4

The fibre is easy to elongate like wool, acetate, rayon and nylon.

Question 5

Describe high initial modulus:

Answer 5

Only small amounts of extension occur when a large force is applied ton the fibres. For eg. flax, cotton, and polyester,

Question 6

Fibre Flexibility:

Answer 6

The ability of a fibre to bend related to fibre fineness and stiffness. A fibre that is not flexible is brittle (eg, glass fibre). Flexibility is related to crystallinity (e.g. highly crystalline fibres = low flexibility) As crystallinity increases strength increases and flexibility decreases (and vice versa).

Question 7

Fibre Elongation:

Answer 7

Ability of the textile to extend/stretch when a tensile force is applied. This measurement is reported as a percentage of the initial length – e.g. spandex 600%, glass 2%

Question 8

Elastic Recovery:

Answer 8

Ability of a textile to return to its original dimensions after a pulling force is applied.

Question 9

Resiliency:

Answer 9

The ability of the fibre to spring back to its natural position after distortion or compression. In relation, loft is the ability of fibres to return to original thickness after compression. Crimped fibres are generally more resilient than straight fibres. Different fibres can have different levels of resiliency.

Question 10

Order these fibres from most to least resilient:
Wool, modacrylic, polyester, silk, acrylic, flax, nylon, acetate, cotton, olefin, rayon.

Answer 10

Polyester, wool, nylon, modacrylic, acrylic, olefin, silk, acetate, cotton, rayon, flax.

Question 11

Abrasion Resistance:

Answer 11

The ability to withstand a frictional force (rubbing) applied to its surface. Flat, flex and edge abrasion can occur.

Question 12

Give an example of where flat abrasion can occur.

Answer 12

Bed sheets, carpets

Question 13

Give an example of where edge abrasion can occur and what it is.

Answer 13

When a folded edge is rubbed. Ie. edge of collar or cuffs.

Question 14

Give an example of where flex abrasion occurs and what it is.

Answer 14

This is the bending of fibres which creates internal friction. Ie. backs of knees in trousers, folding/unfolding table linens.