Clevertex - Grado Zero Espace Srl

These fibres are branded under the name Bekinit ® . In contrast to bundle-drawn fibres, Bekinit fibres ®
have a rectangular cross section. Additionally, they are thicker, compose of more crimp and are less
expensive due to a shorter production process time. It has to be noted that the bundle-drawing
process takes approximately six months [10].
Metal fibres may also be produced by thermal methods based on processing the fibres through direct
extrusion from the melt. The challenge of metal melt spinning compared to melt spinning of glass or
polymers is that the melt viscosity of metals is approximately 100 times lower than of glass and
polymers. Thus, it might occur that melt fracture easily arises and instead of fibres only droplets are
formed. In the following, we refer to some methods for metal fibre production by using a coagulation
bath.
In the Taylor process a metal rod is utilised, which is put into a glass tube. Both, the material and the
glass tube, need to possess a comparable melting point to draw them at the same time. When heating
the whole system, the metal rod melts and the glass tube gets soft. In this state, the glass tube can be
drawn and forms a very thin hollow glass thread, with the metal as a filler material. The glass casing is
afterwards removed from the metal either by crushing with a roller, or by ultrasound or chemical
separation and the result is a very fine metal fibre (diameter < 50µm).
Continuous production of metallic fibres is achieved by melt spinning in a rotating fluid. During this
process, metals or their alloys are molten and overheated in a gas atmosphere at high temperature
and pressure. The liquid surface is charged with an inert gas excess pressure. Due to the high
pressure, the melt can be pressed through a nozzle. Having been pressed through the nozzle, the
fibre is submerged as a free jet at a defined angle in a laminar flowing cooling agent. The solidifying
fibre is accelerated through the rotation and through the density difference between the metal and the
cooling agent at the inside of the drum, where it cools down to the temperature of the cooling agent.
Extraction takes place either continuously or discontinuously depending on the batch size.
A further possibility to result in melt spun metal fibres is the usage of the melt extraction process. In
this procedure, a water-cooled extraction roller rotates in the melt batch. The roller is usually a multiple
blade with v-shaped edges with which the mass is solidified and short fibres are pulled out. A
magnetic field is created at top of the melt batch to prevent waves occurring at the melt’s surface. With
this procedure, it is possible to process materials like aluminium and tin fibres that cannot be produced
by conventional methods due to their brittleness.
The advantages of metal fibres are their strength, biological inertness and ready availability in textile
form at low costs. Due to its inertness it is not sensitive to washing or sweating.
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