Wool Research

Numerous university textile departments and institutes continually research wool and it's properties. Amongst the foremost of these are CSIRO Australia's National Science Agency and AgResearch, New Zealand’s largest Crown Research Institute - an independent government-owned research and development organisation. The following information has been extrapolated from a variety of research work carried on in various academic research organisations, as well as from academic journals.

UV Protection Factor of Merino Wool

The use of clothing as a means of sun protection has been recommended in recent education campaigns. However recent academic studies show that contrary to popular opinion, many fabrics offered an insufficient ultraviolet protection factor (UPF). Light cotton and linen fabrics do not give sufficient protection against sun damage and skin cancer, nor do suncreams.

In a paper first published in BMC Dermatology 2001, 1:6 doi:10.1186/1471-5945-1-6, Consultant Dermatologist Dr Thilo Gambichler investigated 236 apparel textiles used in spring/summer clothing collections.

According to Dr Gambichler's study, more than half the fabrics tested failed to satisfy the European recommended standard for UV protective clothing of UPF30. Of the fabrics tested, only wool, polyester and some fabric blends offered a UPF factor of 30+.

The most popular natural summer fabrics performed worst in the tests. Most of these, including linen, fell well below the recommended UPF standard. The most popular synthetic fabrics also performed poorly in the tests, with 89% of viscose samples failing the test.

Best UV Protection:

In all the tests, only one fabric offered the best protection - Merino. Of the samples tested, the worst UPF merino provided was 40+, whilst the majority of the Merino samples provided a UPF of 50+.

Of the fabrics tested that achieved a UPF of 40+, all except the merino samples were either heavier or thicker than the merino.

Protection from hot and cold

Merino's insulation capacity has made it synonymous with warmth, yet the ability to insulate the wearer from extremes of cold also helps protect the individual from excessive heat. Like the Thermos™ that keeps hot beverages hot and cold beverages cold, Merino insulates you from the worst of the ambient temperature. This explains why Merino has been worn by both Shackleton on his Antarctic adventures and by the Bedouin of the Sinai. No polyester or other synthetic outperforms merino in either hot or cold conditions.

Humidity control

Merino also helps maintain the micro-climate above the wearer's skin by buffering changes in humidity.

Moisture transport

In hot climates or during strenuous exercise, the micro-climate above the skin becomes saturated with vapour, which will make the individual clammy unless their clothing can absorb and release this moisture. The ability to absorb moisture vapour expressed as a percentage of its dry weight is known as the fibre's regain. For synthetics the regain can be as low as 1%, for cotton it's 24%, while Merino has the highest regain with an ability to absorb 35% of its own dry weight in water. This higher regain means that Merino is better able to absorb the moisture vapour produced by the wearer and so lower the humidity in the micro-climate between the skin and the garment.

In CSIRO trials it was found that Merino transported 27% more moisture away from the body than polyester fabric of identical construction. Wearers also felt less clammy when wearing merino than wearing polyester.

Insulation due to trapped air

Since the conductivity of air is less than a tenth that of most textiles, the thermal insulation provided by a fabric is due not to the fibres themselves but the air trapped between the fibres. Merino is much finer than most other textiles, so, for a given weight, it contains more air spaces, and hence provides greater insulation.

Summary

Merino's superior insulation and its ability to absorb and release moisture mean it is better able to keep the micro-climate near the wearer's skin at a comfortable temperature and humidity. Plus, researchers at the University of Graz, amongst the leading experts in the field, have found that athletes wearing clothing that transports the sweat outward have a more rapid increase in lactic acid than athletes wearing clothing made of wool. Wool's natural ability to absorb, hold and gradually release moisture, maintaining an optimum body-climate, slows down the build up of lactic acid in the muscles where it can cause pain and damage.

Comparison of Merino Wool and Polyester

Merino's superior overall climate control was verified in a study conducted by the Ergonomics Unit at the Polytechnic Institute of Wales. The Institute compared a wool comforter with a synthetic comforter of equivalent weight and construction and the physiological data showed that the heat under the wool comforter was significantly lower 100% of the time. They also measured the humidity next to the skin and found that under the wool comforter it was lower 71% of the time. Research carried out by Dr S R Collie, Dr A Tasker & M F Hnat, at AgResearch (Report CLR 10/17), also found that that in comparison with a synthetic equivalent Merino is likely to be the best option for maintaining thermophysiological comfort and wellbeing in a wide range of conditions. In particular:

Merino was found to have moisture vapour absorption that is over 80 times higher than synthetics. This means that there is less likelihood of getting damp (due to condensation of perspiration) in areas where moisture vapour transmission is restricted, such as between layers.

Merino has lower air permeability but the same moisture vapour transmission as synthetic. This gives better protection from chilling due to unavoidable air movement from convection (loss of warm air around the body) and drafts, while still allowing moist air to be dispersed.

Whilst this particular trial was in relation to the benefits of wool bedding, the benefits demonstrated, i.e. better temperature and moisture management under wool than under synthetic fibre products, leading to more restful sleep, the thermophysiological comfort test results are equally applicable to Merino clothing, in particular to baselayers. These, when, combined with Merino wool's low flammability, volatile absorption properties and non-irritant properties, indicate that it is the ideal fibre type to use not only for bedding, but also for outdoor clothing.

Flammability

A simple measure of the flammability of a material is its ‘limiting oxygen index’ or LOI. This is defined as the minimum concentration of oxygen in a mixture of oxygen and nitrogen that will just support flaming combustion. The higher the LOI of a material, the less flammable it is, and if the LOI is above 21 then the material is considered ‘self-extinguishing’. This is because the proportion of oxygen in air (which is mostly oxygen and nitrogen) is 21%. The limiting oxygen index for wool is 25.2, while for polyester it is 20.6 [21]. Therefore, wool is less flammable than polyester, and would self-extinguish in the absence of an ignition source.

Polyester would not self extinguish as readily. In addition, polyester, like many synthetic fabrics, melts when exposed to high heat. The melted polyester can adhere to the skin causing more severe burn injuries than wool, which decomposes (breaking down to ash) when subjected to high heat. Wool is, therefore, intrinsically safer in sleepwear and bedding textiles than polyester, which may need a chemical treatment to achieve suitable flame retardence. It should be noted also that fabric construction has a major influence on how readily it will burn. Very lofty low density fabrics (such as fleece fabrics) ignite and burn more rapidly, especially if they have a fuzzy surface.

Absorption of volatiles

It is now widely known that the chemical properties of wool allow it to absorb volatile compounds from the indoor environment. Wool carpets are able to play a role in controlling indoor air pollution, absorbing nitrogen oxides, sulphur oxides and formaldehyde, all of which can contribute to sick building syndrome, and it is likely that wool in other forms (such as bedding and apparel) can play a similar role, albeit on a scale proportional with the amount of wool present.

As well as absorbing and trapping potentially harmful volatile chemicals, the absorbent nature of wool allows it to trap odour-causing compounds, which can be advantageous in items to be worn next to the skin for a prolonged period.

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