Study Unit 3.3 Secondary Properties

Question 1

The secondary properties

Answer 1

The secondary properties of fibres relate more to the performance/use of textiles and it is these properties that consumers are usually more aware of.
Not all the fibres possess all the desired secondary properties.
Finishing processes can also affect the secondary properties of certain fibres.
These processes can introduce or improve desirable properties that are absent or present at a low level, although sometimes this can harm other inherent fibre properties.
It is also important to remember that external conditions of temperature and humidity affects a number of properties, such as strength, abrasion resistance, moisture absorption and elasticity.

Question 2

The secondary properties

Answer 2

1. Density
2. Lustre
3. Colour
4. Abrasion resistance (and pilling)
5. Elasticity
6. Moisture absorption (wicking and static)
7. Heat conductivity
8. Resiliency
9. Dimensional stability
10. Thermal
11. Resistance to chemicals, micro-organisms and insects, and stability to light

Question 3

1. Density

Answer 3

The density of a fibre is the mass per unit volume and is expressed as grams per cubic centimetre. Low density fibres can be made into thick fabrics that are more comfortable than higher density fibres made into heavy, thick fabrics.

Question 4

2. Lustre

Answer 4

The lustre of a fibre refers to the sheen, shine or gloss of a fibre and the amount of light that the fibre reflects determines it. Lustrous fibres reflect a large amount of light and the fabrics are used for formal apparel and furnishings. Matte or dull fabrics reflect little light and are used more for less-formal looks. Silk has a high lustre compared with cotton. The lustre of manufactured fibres can be varied during manufacture to give bright, semi- bright and matte fibres. Yarn and fabric structure, and finishes can increase or decrease the lustre of fibres.

Question 5

3. Colour

Answer 5

While the colour of manufactured fibres is usually white or off-white, when manufactured, the colour of natural fibres varies from white to grey, tan or black. Manufacturers can use bleaching and dyeing processes to change fibre colour.

Question 6

4. Abrasion resistance (and pilling)

Answer 6

Abrasion resistance is the ability of a fibre to withstand the rubbing or abrasion it gets in everyday use.
Thus, yarn and fabric constructions influence abrasion resistance.

Question 7

• Pilling

Answer 7

Pilling is the balling up of fibre ends on the surface of fabrics. It is also a characteristic of many strong manufactured fibres. Abrasion from normal wear and cleaning causes the fibres to unravel and the loose ends ball up on the fabric surface. Natural fibres like cotton, linen or wool may also pill at times, but the balls of fibres are usually removed during laundering because the fibres have a lower tenacity and the pills break off. Fibre length, yarn and fabric constructions also play a role in pilling.

Question 8

5. Elasticity

Answer 8

Although scientists differentiate between elongation (the ability of a fibre to be stretched) and elastic recovery (the ability of a fibre to recover from strain) to simplify matters we will refer to just the elasticity of a fibre.
This refers to a fibre’s ability to stretch when strain is applied and return to its original shape when the strain is removed.
Rubber and spandex are the two most elastic fibres.
Fabrics with poor elastic recovery tend to stretch out of shape. Fabrics with good elastic recovery generally have good resilience.
A fibre’s ability to stretch and recover with movement plays a role in the comfort of a textile.

Question 9

6. Moisture absorption (wicking and static)

Answer 9

A fibre needs good moisture absorption properties in order to accept dyes and finishes. Moisture absorption also influences comfort. It is far more comfortable to wear a natural fibre such as cotton next to the skin rather than nylon, which absorbs very little perspiration. On the other hand, nylon dries quickly after washing. Hydrophilic fibres absorb moisture readily. Hydrophobic fibres have little or no absorbency. Hygroscopic fibres absorb moisture from the air.

Question 10

• absorption

Answer 10

Absorption refers to process of fibres to take up water. It also refers to water that the surface of the fibre holds in a thin layer.

Question 11

• wicking

Answer 11

Wicking is the rapid movement of adsorbed moisture on the surface of a fibre. A fibre could have poor water absorption but could still be comfortable to wear because moisture such as perspiration is wicked away from the skin to the outside, where it rapidly evaporates. Manufactured fibres can be designed to increase their wicking ability. Blends of fibres and finishing treatments, including nano- finishes, are used to increase wicking.

Question 12

• static build up

Answer 12

Water absorption also influences the build up of static electricity in fibres. Hydrophobic fibres are more likely to develop a static charge which results in static cling and fabrics that are uncomfortable to wear in certain conditions.

Question 13

7. Heat conductivity

Answer 13

A fibre’s ability to conduct heat away from the body is known as its heat conduction property. A fibre such as wool that has poor heat conduction abilities will not move heat away from the body but retain it, and will therefore be warm to wear. A fibre, such as cotton, which has good heat conduction abilities, will be cool to wear. The way in which a yarn or fabric is constructed also has an influence on the heat conductivity. Silk has poor heat conduction abilities and should be warm to wear but a silk fabric can be so finely woven that it will be cool to wear.

Question 14

8. Resiliency

Answer 14

Resiliency is the ability of a fibre to return to shape after bending, stretching or flattening. A resilient fibre or fabric will have good crease recovery. A fibre with good resiliency, such as wool, is also a good carpet fibre choice, as the flattened carpet pile will rapidly regain its shape and restore its appearance. A resilient fabric will have good wrinkle resistance.

Question 15

9. Dimensional stability

Answer 15

Dimensional stability is the ability to retain a given size and shape through use and care. Dimensional stability includes the properties of shrinkage resistance and elastic recovery. A fabric that shrinks is smaller after laundering and it will have poor fit. Untreated wool fibres are susceptible to shrinkage during washing as a result of the scales on the surface of the fibre.

Question 16

10. Thermal

Answer 16

Thermal properties are important in determining how a fibre should be washed and ironed. Most manufactured fibres will soften and melt when exposed to heat. Fibres, such as nylon and polyester, are thermoplastic and will melt if exposed to a too hot iron. Natural fibres are not thermoplastic but they may scorch or burn when ironed at high temperatures.
A fibre’s flammability usually refers to a reaction to open flame. This property is important in fibre identification. It is also an important consideration when selecting fibres for particular end-uses such as nightwear. Finishes can be applied that reduce fibre flammability.

Question 17

11. Resistance to chemicals, micro-organisms and insects, and stability to light

Answer 17

A fibre’s ability to resist attack from chemicals, micro-organisms and insects, and its stability to light is important in the care and maintenance of the fabric, and is largely dependant on the chemical composition of the fibre. For example, wool is susceptible to attack from the larvae of clothes moths, so manufacturers need to be careful with the storage of wool garments. Also, they can apply finishes to fibres which improve a fabrics resistance to chemicals, micro-organisms and insects, and its stability to light.

Question 18

Price

Answer 18

Apart from a fibre’s primary and secondary properties, there are also economic considerations. The fibre must be available at a competitive price with a consistent supply and quality to meet demands. The cost of producing and processing the fibre must not be higher than what the consumer is willing to pay. The price of fibres vary according to a number of factors including: changes in the price of raw materials, fibre fineness, finishes applied, additives, special properties, such as high tenacity, climatic conditions, economic trends, and supply and demand factors.