Merino Wool

WHY WE LOVE MERINO

Wilderness Wear has a 20-year history of using wool in our sock manufacturing. Over recent years we have researched, tested and developed our woollen thermal underwear range as well. The Pure Australian Merino wool we use has many advantages over synthetic fabrics with wool being a true, natural, miracle fibre.

The Merino sheep from which we source our wool are bred and nurtured in the Western District of Victoria and the cooler regions of Tasmania. This wool comes from sheep of special breeding and selection. Extremely thin fibres with low micron counts and long staple fibre lengths are used to ensure unsurpassed comfort when used as a next to skin layer.

BENEFITS OF WOOL

IT'S FIRE RESISTANT !

(Of particular relevance to fire services garments.)

Merino wool causes no itch due to its very low micron (18.5) count.

Merino wool has natural, breathable fibres that pull moisture away from your body which helps keep you dry and comfortable.

Merino wool will keep you warm when it’s wet. Although wool is naturally hydrophobic and repels water, it is capable of holding 30% of its own mass in vapour. This is due to hydrogen/oxygen attractions that keep the water stored inside fibres still, allowing air to be present between fibres. The water absorbed inside the complex wool fibre is affected by your body heat and the Merino fibre actively works to release the moisture to the external environment. This procedure is increased by your body warmth.

Merino wool has the ability to cool you off when you sweat.

Merino wool is extremely durable. You can stretch and bend the fibres without damage. Non-pilling is the result.

Merino wool is highly UV resistant with a natural sun protection factor of UPF50+.

Merino wool has natural anti-microbial properties, which means you won’t smell as bad as you would in synthetic underwear. When you wash Merino wool, it dries quite quickly.

Merino wool is biodegradable and comes from a renewable source.



Fire resistance

A number of factors contribute to make Merino the most naturally fire resistant of all commonly encountered textiles.



High ignition temperature

Merino is less likely to burn than most textiles. Compared to cotton, which catches light at 255 degrees, the temperature must reach 570-600 degrees before Merino will ignite.



High Limiting Oxygen Index

In order for fire to be sustained under the standard test conditions used to measure Limiting Oxygen Index, Merino requires a very high level of oxygen – significantly higher than occurs in nature. The proportion of oxygen in the atmosphere is 21%, more than sufficient for cotton, rayon, nylon and polyester to burn. However, Merino requires an oxygen level of 25.2% – more than 4% higher than ambient.



Low heat of combustion

When it does burn, Merino releases less heat than common synthetics. Its heat of combustion is a low 4.9 Kcal/g while polyester is 5.7 Kcal/g, cotton is 3.9 Kcal/g and nylon is a very high 7.9 Kcal/g

Low rate of heat release

Though cotton has a lower heat of combustion than Merino, its rate of heat release is much higher and the wider fire science community now recognises that it is the rate of heat release that determines the real hazard in fire situations.

Self-extinguishing

If Merino does catch alight, it tends to self-extinguish. The Merino fibre contains naturally high levels of nitrogen – an element commonly used as a fire retardant – and when it is heated sufficiently to combust, it tends to produce insulating foam that excludes oxygen and hence puts out the fire.

Won’t melt

While polyester melts at 252-292° and nylon succumbs at an even lower 160-260°, Merino never melts so it can’t stick to the skin like many common synthetics, sparing burn victims from significant medical complications.

Summary

A high ignition temperature, a low heat of combustion and the necessity for an oxygen level higher than occurs in nature means Merino is less likely to catch alight than most synthetics. But, its low rate of heat release, its tendency to produce a foam that self-extinguishes, and the fact that it never melts further explain why Merino has the highest natural fire resistance of all commonly encountered textile fibres.



Sources:

CSIRO, “Flame resistance of wool”
Flame Resistant Fibres and Fabrics (2003), Performance Apparel Markets, Issue 6, 3rd Quarter, 2003
Benisek, L. (1976) Development of Flame Resist Treatments for Wool, Wool Science Review No. 52, pp 30 – 63.
Horrocks, A.R., (2003) Flame-retardant finishes and finishing, in: Heywood, D. (Ed.) Textile Finishing, Bradford, Eng.: Society of Dyers and Colourists
Horrocks, A. R. et al. (2005) Developments in Flame Retardant Textiles – a Review in Polymer Degradation and Stability. Vol 88, Issue No. 1, April