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A NATURAL BARRIER AGAINST FIRE

Wool is composed of a protein called keratin. Hydrolysis has revealed that wool contains around twenty different amino acids. The molecular structure of wool is as follows:

a) Long straight chains resulting from the condensation of the amino acids.

b) Side chains connecting the first together and resulting in links and bridges between the various chemical groups.  

Wool is therefore a living, loose fiber composed of a substance (keratin) that does not burn well. Its poor combustibility is due to the presence of a substantial quantity of nitrogen in the macromolecular chains.

Wool can absorb a significant amount of humidity, compared to other fibers, as shown by the table of absorption rates (at standard conditions of 428*F  and 65% relative humidity). Wool batting are available at our online store. 

WOOL AND HUMIDITY

Combed wool 

Cotton 

Polyamide

Polyester

Acrylic 

18,25%

 8,50% 

 6,25%

       3%

       2% 

In these conditions, wool can absorb around nine times more water than  acrylic, six times more than polyester and three times more than polyamide.

The presence of high levels of humidity associated to wool contributes to its resistance to fire. 

Although it is well know that the natural fire-resistant properties of wool stem from its chemical composition, what is more important are the safety criteria, such as: flammability, heat of combustion, combustion rate, extinguishability, melting, smoke and toxic gas emission. 

 

 

 

 

FLAME SPREAD RATE AND EXTINGUISHABILITY 

These two characteristics are interrelated: low flame spread rate implies a low flame factor, which means a low heat source and therefore high extinguishability. These criteria have a direct influence on the time available for the evacuation of the premises and intervention of firefighters, In all circumstances, wool chars: it burns but does not produce flames. 

Melting, and more specifically the emission of ignited, transfers the flame sources and decentralizes the seat of fire, resulting in the fire spreading to greater proportions and causing serious burns.

Wool does not melt. When it burns, it leaves a cold, insulating ash. 

FLAMMABILITY 

This is the ability of a material to ignite when exposed to a flame or heat source (cigarette, burning paper, overheated electrical circuit, for example).  This criteria is closely related to the ignition temperature, at which  a material will ignite spontaneously. 

As shown in the table below, wool needs a temperature of 1112°F to ignite, making it the most efficient of the fibres examined here. 

IGNITION TEMPERATURE IN °f

Material

 

Cotton 

Viscose 

Polyester

Polyamide

Acrylic 

Polypropylene 

Wool 

*F

752

788

842

986

1040

1058

1112

HEAT OF COMBUSTION 

 

 

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