Wool’s range of desirable properties make it a valuable material for many different purposes, from high-end fashion to fire-resistant products and heavy-duty carpet. Discover how wool’s unique structure creates its many desirable properties.
Wool’s unique cellular structure gives it a number of desirable properties. Most properties are typical of all wool, but there are some differences in wool from different sheep breeds. The differences affect the appearance and feel of the wool and what it’s used for.
Wool’s surface structure
Wool fibres have a unique surface structure of overlapping scales called cuticle cells. The cuticle cells anchor the fibre in the sheep’s skin. Wool’s surface is very different to typical synthetic fibres, which have a very smooth surface.
Cuticle cells give ability to felt
Felt is created when wool fibres are agitated in water – they slip over one another and the scales interlock, preventing the fibre from returning to its original shape. The process can be controlled to create very dense fabrics such as felt and wool blanket and jacket fabric, but can also be caused unintentionally during laundering and ruin a garment.
Fibre surface is water repellent
The cuticle cells provide a tough exterior, protecting the fibre from damage. The cells have a waxy coating, making wool water repellent, but still allowing absorption of water vapour1. The water-repellent surface makes wool garments naturally shower-proof and also reduces staining because spills don’t soak in easily.
Wool’s interior structure
Interior structure creates flexibility and absorbency
The matrix also creates wool’s fire-resistant and antistatic properties.
Absorbency creates comfort
When wool absorbs moisture, it produces heat2, so if you go from a warm room into a cold, damp night wearing a wool jersey, the wool picks up water vapour from the air, keeping you warm. The reverse occurs when you go back into the warm room – the moisture in your jersey passes into the atmosphere3, cooling you down. Tiny pores in the cuticle cells allow water vapour to pass through the wool fibre. This makes wool comfortable to wear in both warm and cool conditions4.
Arrangement of interior cells creates fibre crimp
There are 2 main types of cell5 in the cortex6 – orthocortical and paracortical – and each has a slightly different chemical composition. In finer fibres, these cells are arranged in 2 distinct halves. In coarser fibres, the arrangement is less distinct.
These cells create the crimp in wool. The 2 types of cell expand differently when they absorb moisture, causing the fibre to bend. When the cells are arranged in 2 halves, there is more crimp, and the more random arrangement in coarser fibres creates less crimp, so crimp relates directly to fibre diameter.
Fibre crimp affects wool’s properties
The crimp in wool fibres makes it soft and springy to touch. It also adds bulk and traps a large volume7 of air between the fibres, giving it good insulation8 properties. Finer fibres with more crimp such as Merino create fabrics that drape better than coarser fibres.
Related content
This article is a handy curation of our resources looking at some of the innovative wool textiles being developed at AgResearch.
Useful links
What is Wool Insulation? provides an explanation of how wool’s properties make it suitable for insulating buildings from HomeQuestionsAnswered.
Find out more about wool from Britannica Kids.
The chemical and physical structure of Merino wool is a downloadable PDF with a detailed and technical account of the physical and chemical properties of Merino9 wool, from the CSIRO website.
You may also be interested in seeing the New Zealand Sheepbreeders Association website.
- water vapour: The gas phase of water.
- heat energy (heat): Heat energy: the transfer of energy in materials from the random movement of the particles in that material. The greater the random movement of particles the more heat energy the material has. Temperature is a measure of the heat energy of a material.
Heat: the flow of energy from a warm object to a cooler object. - atmosphere: 1. The layer of gas around the Earth. 2. (atm) A non-SI unit of pressure equivalent to 101.325 kPa.
- condition: An existing state or situation; a mode or state of being.
- cell: 1. Building block of the body. A human is made of millions of cells, which are adapted for different functions and can reproduce themselves exactly. 2. A simple electrolytic device that enables chemical energy to be transformed into electrical energy.
- cortex: 1. The cerebral cortex, or just cortex, is often referred to as grey matter because the nerves it is made up of lack the insulation that makes other parts of the brain appear white. It covers the outer portion of the cerebrum and cerebellum. In humans, it is 2–4 mm thick and plays a central role in many complex brain functions including memory, attention, perceptual awareness, 'thinking', language and consciousness. The cerebral cortex consists of folded bulges that create deep furrows. The folds in the brain add to its surface area and therefore increase the amount of grey matter and the quantity of information that can be processed. 2. interior of wool fibre.
- volume: 1. The quantity of space occupied by a liquid, solid or gas. Common units used to display volume include cubic metres, litres, millilitres, tablespoons and teaspoons. (Volume can refer to a large quanity of something). 2. The degree of sound intensity or audibility; loudness.
- insulation: Materials used to reduce the rate of heat transfer.
- merino: A breed of sheep that produces very fine wool.
