The wool fibre and its applications Dr Geoff Naylor CSIRO

This lecture  Introduction to the fascinating world of the wool fibre and its wonderful structure, which results in its many splendid properties.  Start with a close look at the fibre.

Wool Structure: not just a ‘soup’ of wool molecules

Warmth  In cold environments an important function of textiles is to keep the body warm.  Clothing reduces the rate of heat loss from the body.  This physical property is called thermal insulation.

Warmth  Still air is nature’s best insulator – much better than any fibre.  It is the air or spaces in textiles that give warmth.  Wool’s natural crimp and high bulk means it naturally traps lots of air. Hence it is famous for warmth, particularly in bulky knits.

Wool: naturally absorbs water vapour and is breathable  Wool is an active fibre.  It is able to absorb and desorb moisture vapour as conditions around it change.  This gives wool is its fantastic ‘comfort’ properties and makes it ‘breathable’.

Wool: naturally absorbs water vapour and is breathable 40 30 wool cotton polyester  Scientifically, the amount of water a fibre can absorb internally, i.e. without feeling wet, is called its ‘regain’.  This depends on the relative humidity of the surrounding air.  Wool comes first in this comparison, being able to absorb up to 35% of its weight in water before feeling wet. Re g ain 20 10 0 20 40 60 80 100 120 Re lative H u m id ity Fib re Sa tu ra tio n re g a in % Wo o l 35% Co tto n 24% Po lyam id e 7% Po lye s te r 1% Po lyo le fin .05% Po lyac rylo n itrile A ra m id 6.5%

Wool: naturally absorbs water vapour and is breathable  The human skin is very sensitive to very small changes in temperature and humidity in the microclimate next to the skin. R a te o f m o is tu re va p o u r p re s su re in c re a s e polyester sweating starts Moisture Evaporation and Transport sportwool 4 m in u te s o f e xe rc ise 2 6 8  During physical activity wool can significantly reduce feelings of dampness and moisture discomfort. Heat Loss Pressure

Wool: naturally absorbs water vapour and is breathable Synthetic Fibre Wool Fabric Rainproof fabric Synthetic fibres absorb very little moisture vapour Rainproof fabric Wool absorbs moisture vapour rapidly Skin Big build-up of humidity Skin Reduced humidity Wool is hygroscopic which means it can easily absorb water vapour. This property counteracts the build-up of clammy, humid conditions within clothing.

Active heating  When wool absorbs water it actually generates heat!  The amount of heat can be quite significant. When a kilogram of dry wool is placed in a moist environment the amount of heat it releases is about the same as an electric blanket running for eight hours.  This active generation of heat is unique and can reduce ‘thermal shock’ during the transition from indoors to outdoors in wet winter climates.

Wool: water repellent  As well as absorbing moisture vapour, the surface of the wool fibre naturally repels water. Small drops of water do not readily soak into a wool fabric but stay on the surface as droplets, which can easily be shaken off.  This is great for outdoor clothing, such as golf wear.

Wool: water repellent and anti- soiling and spills on wool carpets.

Wool – naturally flame resistant Ignition Source  Fuel, heat and oxygen are all essential for combustion. Remove one and the fire extinguishes.  Wool contains high levels of nitrogen and sulphur, which are natural fire retardants, i.e. hard to ignite.  A natural black char forms, creating an insulating layer separating the fuel and oxygen. Fuel Oxygen The Fire Triangle

Wool: shape retention  Wool has excellent tailorability, drape, style and shape retention.  It can be shaped and set in a multiplicity of ways; for example, the three-dimensional shapes required for a suit.

Glass Transition Thermal Splicing Yarns Wool: shape retention  Depending on temperature and water content (regain) wool can be (i) stiff or ‘glass like’ or (ii) softer or ‘rubber like’.  This is used in tailoring to form and lock in the required shape. Co h e s ive / Te m p o ra r y S e ttin g o f Wo o l 18 0 160 14 0 12 0 10 0 80 60 40 20 -­‐2 0 -­‐4 0 Pressing a Crease Glass Transition Thermal Splicing Yarns Removing Twist Liveliness Rubber Like Te m p e ratu re (o C ) Glass Like 0 5 10 15 20 25 Re g ain ( % ) 30 35 40

The wool fibre contains a number of Wool: shape retention Pe rm a n e n t S e ttin g o f Wo o l H O H O H O N C C N C C N C C  Permanent creases can be achieved by rearranging the internal bonds in the wool fibre. H R1 H CH2 H R3 S S H R4 H R5 H H2C H R6 N C C N C C N C C N C C H O H O H O H O The wool fibre contains a number of S S S S S S S - S S S- S S S S S S S S When the fibre is understress, the dissulfide bonds can rearrange

Wool: exquisite drape

Elasticity

Elasticity  Wool wears well not because of its strength but because of its high extensibility. This allows wool to stretch and recover with minimal breakage or damage. 300 250 200 15 0 10 0 50 0 5 10 15 20 25 30 35 40 45 50 55 60 S tra in / % 0% 28% 84% 100% S tre s s/ M Pa

Odour absorption  Sweating is the body’s natural way to regulate its temperature.  If sweat remains on the body for several hours, bacteria can develop and lead to body odour.  The moisture absorbing nature of wool and its breathability helps control this.