The Unique Properties of Wool
The Unique Properties of Wool
Wool existed thousands of years ago and always will. But what makes this natural fiber so unique? And above all, how can it compete with synthetic alternatives?
Sheep’s wool was a true godsend for humankind – in the search for warming materials suitable for the production of clothing and which naturally bring desirable properties, wool was the first choice.
Numerous sheep line the green hills. You hear only their bleating and the plucking of grass. A dog guards them attentively. These are exactly the perfect conditions for our favorite renewable resource.
Sheep were among the first animals to be domesticated in Mesopotamia about 10,000 years ago. However, different societies have since attributed different values to them, and therefore they have been bred with different characteristics.
Nowadays, we can find different types of sheep and wool all over the world. This is because sheep wool, by nature, has a lot of excellent properties that synthetic fibers cannot achieve.
Wool is antibacterial, low odor, water and dirt repellent, and provides cozy warmth in winter and pleasant freshness in summer. And, of course, for excellent moisture management.
Wool is antibacterial thanks to the surface structure of wool fibers, and thus at the same time, odorless. While synthetic fibers are smooth, wool fibers have a scaly structure.
Figuratively speaking, they are reminiscent of roof tiles. For this reason, it is difficult for bacteria – and thus also unpleasant odors – to adhere to the fiber.
In addition, wool wicks moisture away quickly so that less sweat accumulates on the skin and odors do not form in the first place. The protein molecule keratin, which is contained in wool, also contributes to the odor-inhibiting effect by breaking down bacteria.
Furthermore, the fiber uses a mechanical self-cleaning process: The fiber core consists of two different types of cells that absorb different amounts of moisture and therefore swell unevenly – this creates constant friction. As a result, the fiber cleans itself over and over again.
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What we appreciate most about wool is its excellent moisture and temperature regulating properties. In winter, it keeps your offspring comfortably warm. In summer, it provides pleasant freshness.
Wool warms, among other things, due to its insulating effect. Did you know that air can make up to 85% of the total volume of the crimped fibers?
The crimping creates air pockets that store body heat instead of transmitting it. Air is thus a poor conductor of heat but an excellent insulator. By the way, the well-known onion look is also based on this principle!
So sheep’s wool does not warm by itself, but because it does not allow body heat to escape. The air serves not only as an insulating layer against cold in winter but also against heat in summer.
Incidentally, double-walled windows also make use of this insulation principle: The air trapped between the panes has an insulating effect in both summer and winter.
The thermo-regulating properties of the natural fiber are maintained even in contact with rain. In other words, even when it gets wet, wool – unlike down – still feels pleasantly warm.
The wool fiber is structured in such a way that moisture moves into the fiber core while the surface remains dry. Nature has also endowed wool with a special warming mechanism.
Through an exothermic process, the fiber actively heats up as it absorbs moisture. When the polar wool fibers collide with water molecules, they release heat of absorption.
This can increase the temperature by up to 10 degrees. This happens until the fabric is saturated with water molecules. However, even a soaked wool fabric can still provide warmth because mechanical frictional heat is generated during movement.
Tip: In case of heavy or long rain, you should still fall back on your included rain cover.
Again, back to the moisture thing. We have already indicated that the wool fiber conducts moisture inside and thus has a unique moisture management. The numbers on this are truly remarkable: wool’s interior fiber can absorb up to 35% of its own weight in moisture without feeling wet. In comparison, synthetic fibers can only absorb less than 10% of their dry weight.
Wool fibers owe this property to their hydroscopic structure: the surface remains dry because it repels water. The inside of the fiber, on the other hand, can bind a particularly large amount of water vapor especially quickly.
This phenomenon is extremely practical not only when it rains; the fiber network also conducts perspiration quickly into the interior through the smallest channels. Thus, the wool fiber can compensate for fluctuating moisture levels in its environment particularly well, thanks to its structure.
Speaking of sweat, there is another function worth mentioning. We have already learned that insulation is not the only thermal mechanism that wool has.
It’s the same with cooling in the summer. When the ambient air is warm, the absorbed sweat evaporates faster on the outside of the fabric.
However, this evaporation process requires energy. This is extracted by the molecules of the sheep’s fiber in the form of heat. The wool fibers cool down, and evaporative cooling occurs.
Thanks to its hygroscopic structure, wool also keeps dust mites away. They need a damp climate to feel comfortable. This also prevents asthma attacks, which can be triggered by dust mite allergens.
Not only does its antibacterial and thermo-regulating properties make wool an ideal fabric for strollers: wool also repels dirt and water better than other fibers.
You can easily spill something and quickly wipe it up before permanent stains appear in the fabric. This dirt- and water-repellent behavior is made possible by the wool grease lanolin, which is found on the surface of the fiber.
This protective shield keeps water and dirt particles on the surface and prevents them from penetrating into the interior of the fiber. The strong crimping of the fibers also creates a kind of lotus effect:
The water droplets have only a very small attack surface and simply roll-off due to their surface tension.
Wool is also anti-static, so dirt, dust or lint is not attracted to it. In addition, virgin sheep’s wool is a very durable and robust material that can withstand even intensive use.
The fibers can be bent up to 20,000 times without breaking, making them ideal for strollers. The natural fiber also has no tendency to wrinkle. Wool fibers, even when stretched by 30%, retract to their natural shape.
Its complex winding structure provides the necessary elasticity so that the wool does not become flat and hard. Another plus point is that wool is flame retardant.
This means that the temperature at which it ignites is very high, and wool does not burn but chars. So, for example, if a cigarette comes into contact with the fabric, only a single burn mark is created.
In the leaflet folded protein structure, amino acid residues with the same charge lie opposite each other: the leaflet structure of the wool is not stable. After stretching, the wool reverts to the lower-energy helical structure on its own.
Depending on the nature of the amino acid residues, additional bonds such as ionic bonds “salt bridges” or covalent bonds “sulfur bridges” can provide stability to the helix.
Significant, non-polar amino acid residues also play a role here with their van der Waals forces.1
If you look at the natural UV protection of different materials, wool also performs very well. Only polyester offers a higher integrated sun protection factor.
After that, wool, polyamide and silk follow, while cotton, viscose and linen come in last. So if you only look at the natural fabrics, wool has the highest light protection.
In addition, wool is a renewable resource, and fewer chemicals are used as in the production of cotton.
Compared to synthetic fibers, the extraction of wool is more environmentally friendly and conserves resources. Synthetic fibers are, in fact, produced on the basis of crude oil.
This requires not only a lot of energy but also many chemicals. Unlike synthetic fibers, wool is also biodegradable.
Synthetic clothing, on the other hand, takes at least 30 years to decompose.
Wool as a material is incredibly fascinating and has an exciting history that stretches back over 10,000 years.
These natural fibers will continue to play a major role in the future and is already an indispensable material for the production of high-quality functional underwear and outdoor clothing.
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