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The structure of wool fibres

The most profound thing to reflect on is that nature is by far the most sophisticated designer. Functional complexity is built into each individual wool fibre, ranking superior to anything we can try and engineer in a lab!

Wool is one of the oldest fibers known to humankind, with evidence of its use dating back to the Bronze Age. The unique properties of wool make it an excellent material for a wide range of products, from high end apparel to fire-resistant products and heavy-duty carpets!

structure of wool

Discover how wool’s unique structure creates its many properties.

 

Cuticle Scales

The outermost layer of the wool fiber is called the cuticle. Wool fibres have a unique surface structure of overlapping cuticle cells known as scales.

The cuticle cells anchor the fibre into the sheep’s skin just as human hair does. The cuticle cells provide a tough exterior, protecting the fibre from damage. The cells have a waxy coating, making the wool water repellent whilst tiny pores in the cuticle cells allow water vapour to pass through the wool fibre, making wool comfortable to wear in all climates.

The scales overlap like tiles on a roof. The exposed edges of the cells point towards the tip of the fibre, creating a jagged edge. This helps expel dirt and gives it the ability to felt.

Wool felts when the fibres are aligned in opposite direction, and they become entangled. This can be useful in outdoor apparel and upholstery fabrics and but also occurs inconveniently when wool clothing is over-laundered.

 

Cortex

The cortex is the middle layer of the wool fiber and is responsible for most of its mechanical properties.

it is made up of long, twisted chains of keratin, which give the fiber its strength and elasticity. The cortex is highly organized and contains many small, air-filled spaces that help to trap heat and insulate the body. The thickness and density of the cortex can vary depending on the breed of sheep, and this can affect the overall quality and characteristics of the wool.

 

The difference between the para-cortical and ortho-cortical cells

A wool fibre is made up of two main types of cells in the cortex: ortho-cortical and para-cortical, and each has a slightly different chemical composition. In finer micron wools, these cells are arranged in two distinct halves. In coarser wool, the arrangement is less distinct.

This difference in cell types, placed side by side, is what creates wools natural crimp. This is because the two cell types expand at different rates when they absorb moisture, causing the fibre to bend. Therefore, crimp is directly related to fibre diameter.

The crimp in wool fibres makes it soft and springy to touch. It also adds bulk and traps a large volume of air between the fibres, giving it good insulation properties.

 

Matrix

The matrix consists of high sulfur proteins. This makes wool absorbent because sulfur atoms attract water molecules. Wool can absorb up to 30% of its weight in water and can also absorb without feeling wet. and retain large amounts of dye. This additional moisture content also helps wool resist static and is what causes wool to be low agnition temperature, delivery safer clothing and interiors.

 

Helical coil

The helical coil, which is surrounded by the matrix, is tightly coiled structure that forms naturally in the fibers of wool.

The helical structure of wool fibers also makes them more durable and resistant to breakage. The coils help to distribute stress and tension across the fibre, making it less likely to snap or fray. This is why wool is often used in clothing and other textiles that require strength and resilience.

It is a fundamental aspect of the fibre’s unique properties and versatility. It is an important consideration for textile manufacturers, scientists, and environmentalists who are interested in understanding and harnessing the benefits of this natural material.