JEC COMPOSITES MAGAZINE - Issue #142 - September/October 2021 - 23

TFP MANUFACTURlNG
High-performance polymers for fibres
and fibre-reinforced composites
Thomas Gries,
Director of the Institut für Textiltechnik
(ITA) of RWTH Aachen University,
melina sachTleben,
Research assistant
lukasz Debicki,
Head of department Multifilament
Technologies
max schwab,
Key account and industry project manager
Composite Production
M
elt spinning plants with operating
temperatures of up to 400°C
are required for the production
of filament yarn from high-performance
polymers. The Institut für Textiltechnik
(ITA) of RWTH Aachen University is
one of the few research institutions that
has the necessary plant technology on
a pilot scale. Filament yarns and textile
fabrics made of PEEK have already been
successfully produced within research
projects (Figure 1).
Fig. 1: Filament yarn made from PEEK (left) and the
resulting fabric (right)
Reducing cost
ITA's current research efforts go beyond
the mere spinning out of individual
polymers. For example, yarns made
from polymer blends are currently being
explored. The aim of the research is to
produce high temperature-resistant
filament yarn with excellent mechanical
properties while at the same time reducing
the high raw material costs of thermoplastic
high-performance polymers.
By mixing different polymers, properties
can be achieved that none of the raw
materials has on its own. At the same
time, part of the expensive material
can be replaced by a less expensive one
without significant loss of properties.
For this purpose, mixtures of expensive,
high temperature-resistant materials
(PEEK/PEI/PESU) and less expensive
engineering thermoplastics (PC/
PET/PBT) were investigated at ITA.
The expected excellent miscibility of
PEEK/PEI and PEI/PET blends could
be demonstrated for direct filament
extrusion on a co-rotating twin-screw
extruder and thus for the melt spinning
process in general. In addition, filament
yarns were successfully spun out from
both blends.
The results of the investigations show
that with an equivalent blend of the
PEEK and PEI materials, the price of
the up to six times more cost-intensive
PEEK can be significantly reduced by
this blend. In addition, the mechanical
properties
are thermally
Thermoplastic high-performance polymers (HPP) combine excellent
technical properties with low weight, which is why these materials
are used in particular in the automotive and aerospace industries [1, 2]
where continuous service temperatures are usually between 150°C and
260°C [2]. In addition, HPP remain usable in contact with chemicals under
high mechanical stress and under various external influences such
as high and very low temperatures, as well as other environmental
influences [3]. They are also well suited for the production of filament
yarns, with typical materials being PEEK, PPS and PEI.
stabilised.
The blend's drop in stiffness compared
to pure PEEK is only 20%. If the full
mechanical and thermal properties of
pure PEI are not required, the material
costs can also be significantly reduced
by blending in 50% PET. In addition,
other properties of PET, such as excellent
wear resistance, can be combined
synergistically with properties of PEI,
such as good fire behaviour.
As matrix material
High-performance polymers
only
are
high-performance materials
not
in
the form of yarns, another application
is their use as matrix materials for
fibre-reinforced plastics (FRP).
The matrix serves to protect the reinforcing
fibres from external influences
and to ensure their shape. Furthermore,
it introduces the forces into the fibres,
distributes them and absorbs compressive
stresses.
[4, 5].
Thermoplastic fibre composites (TPFRP)
are characterised by advantageous
process costs due to low cycle times
in component production. TP-FRP
N°142 September - October 2021 / jec composites magazine
23
JEC COMPOSITES MAGAZINE - Issue #142 - September/October 2021

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