Chemical, physical and mechanical properties:
|Energy to break
|Silk – Bombyx||15-35||5x10^9||6x10^8||6x10^4|
The toughness of degummed silk fibres is comparable to that of nylon and Kevlar fibres. The elongation at break of silk fibres ranges from 15% to 35%, values that are notably higher than those of cotton and Kevlar and comparable to nylon.
The breaking force is higher than that of cotton, Kevlar and nylon fibres.
Relatively high, greater than wool and acetate fibres.
The average values are similar to those of wool and cotton.
Subjecting the fibres to repeated bending, silk has a resistance between that of wool and cotton.
A combination of strength and toughness
Silk fibres display an unusual combination of strength and toughness that distinguishes them from other natural and synthetic fibres. Silk fibres behave uniquely with respect to mechanical stress. Normally as the tensile deformation rate increases, the strength and modulus increase while the elongation at break decreases. In contrast, silk fibres show an increase in the values of the latter parameter. Therefore, the work to break is greater the higher the deformation rate. This means that silk fibres have an excellent ability to absorb energy at high loading speed rates.
Superior to that of cotton and nylon. Silk fibre is stronger than an equal thickness of steel wire and, more importantly, does not show the phenomenon of yielding before breaking.
Silk has excellent flexibility, enabling the fibres to withstand deformation of 20-25% of their initial length. Up to deformations of -2%, silk completely recovers its size if the stress is removed. The fibres are completely elastic.
Silk is the lightest among natural fibres.
The fibre decomposes when exposed to a heat of 171°C. It has a high resistance to creasing due to the good resilience of the fibres and their ability to recover rapidly from other deformations.
Silk fibres have a low thermal conductivity coefficient.
Thanks to its natural protein formulation, silk is the most hypoallergenic fibre. Silk fabrics are warm and cosy in the winter and comfortably cool when the temperature rises. Its natural heat regulation properties confer this exceptional paradoxical ability to be both warm and cool. Silk is highly absorbent (high hygroscopicity – ability to absorb water-, making it clearly superior to other fibres like cotton, cellulose acetate, polyester and nylon) and dries quickly.
It can absorb up to 30% of its weight in moisture without feeling damp.
Silk is able to absorb perspiration while letting the skin breathe. In addition, silk blends
well with other plant and animal fibres.