Flax, Linen

8-15 usd/kg
Circularity potential
High
Strength
Very high
Production energy
Low
Stiffness
Medium
Embodied CO2
Medium
Density
Medium

Flax is a bast fibre, like hemp and jute, which is extracted from the stalk of the blue-flowered flax plant grown for its seeds (linseed) and fibre. As a natural material, its properties will vary widely, depending on the plant, growing conditions and where in the stalk the fibre came from. Even so, flax and the other bast fibres have impressive qualities. As a technical fibre it competes alongside manmade fibres like glass (GF) and aramid (AF) in terms of strength to weight. And as linen fabric – thought to be one of the oldest textiles – used for clothing and interiors, flax is prized for its high strength, soft hand and high lustre. In addition, it gets stronger when wet, and can soak up around 20% moisture before feeling damp.

Flax is widely cultivated and grows without much need for fertiliser, pesticide or herbicide. Once harvested, the stems require retting to release the fibres from their bundles. This is typically carried out by lying them in water or in the field where they were grown. Microbes breakdown the hemicellulose-pectin matrix that locks the fibres in.

Yarn production involves decorticating and combing the fibres (this is also known as scutching and hackling when carried out by hand) to produce a sliver free from contamination; bleaching; drying; spinning; and winding. Of course, for natural colour fibres, some of these processes are avoided.

Nothing is wasted in production. The seeds are used for food (linseed oil comes from another type of flax plant), the woody core of the stem goes into particleboard or mycelium materials (fungi), and the short fibres are converted into paper or board.



Flax fibre is naturally light brown through dark grey. As a technical fibre, such as required for composites, it is better to keep it as close to its regional condition as possible. Processing the fibre, such as bleaching and spinning, can reduce its strength.

Trade names include Bcomp and their products ampiTex and powerRibs; Biotex from Composites Evolution; Ekoa from Lingrove; and Libeco.


Design properties
Cost usd/kg
8-15
Embodied energy MJ/kg
10-20
Carbon footprint kgCO2e/kg
0.9-1.7
Density kg/m3
1500
Tensile modulus GPa
27-103
Tensile strength MPa
500-1350
Hardness Mohs
1
Thermal conductivity W/mK
0.06
Temperature min-max °C
-40 to 150
Thermal
insulator
Electrical
insulator