A composite is a specific combination
of two or more materials that improves the properties of the individual
components. Nature itself has demonstrated the principle that high-strength
fibres are the most suitable lightweight material for absorbing forces.
Wood, plant leaves, muscles and bones are just a few examples of composite
structures that occur naturally. Today, composites are generally understood
to mean a combination of high-strength fibres and a plastic.
The fibres critically determine the
mechanical characteristics of the composite, such as its strength
and rigidity. The materials generally used are glass, carbon and aramid.
For high-performance composites, exclusively continuous fibres (where
the length of the fibre corresponds to that of the component) are
used in the form of woven fabrics or non-woven fabrics. The matrix
material, too, performs a crucial function. It transfers the forces
between the fibres, provides support to stop them from kinking and
protects them against external attack. A distinction is made between
thermoset plastics and thermoplastics. Thermoplastics such as PP,
TPU, PA and PPS offer clear advantages in terms of forming properties,
design freedom (welding properties, insert moulding with other thermoplastics),
shelf life and ease of recycling. Reason enough for us to use only
these groups of polymers. For detailed information, click on TEPEX®
benefits.
Fibre type Glass
· High tensile and compressive strength
· High tensile and compressive modulus
· Low density (2,6 kg/dm³)
· Low thermal extension
· High thermal stability
· High chemical stability
· Low electrical conductivity
Carbon
Carbon fibres are more expensive than glass fibres, but offer various
advantages:
· Very high tensile and compressive strength
· Very high tensile and compressive modulus
· Low density (1,8 kg/dm³)
· Low thermal extension
· High thermal stability
· High chemical stability
· High electrical conductivity
Aramid
Aramid fibres are used predominantly for bullet-proof and impact-resistant
protective materials. Their advantages are:
· High tensile strength and stiffness
· Excellent impact properties
· Low density (1,6 kg/dm³)
· High chemical stability
Polymer type Plastics
The matrix materials that are used as standard for TEPEX® are
listed briefly below. All thermoplastics could in principle be added
to the list.
PP
Polypropylene is one of the most commonly used thermoplastics. It
has a melting point of 165° C is shaped at 185-200° C, and
its continuous operating temperature is around 90° C. It exhibits
high chemical resistance. PP-based TEPEX® materials are used above
all in the car industry.
PA
Polyamide or nylon are familiar engineering thermoplastics. The following
PA types are used in the various TEPEX® materials:
PA 66: TEPEX® x01, good price/performance ratio and therefore
widely used. Melting temperature is 260° C, forming temperature
approx. 280° C, continuous use temperature 130° C. Used predominantly
for sports articles, industrial applications and the automotive industry.
PA6: TEPEX® x02, again a good price/performance ratio. Easier
to form than and superior surface properties to PA6.6. Melting temperature
is 220° C, forming temperature approx. 240° C and continuous
use temperature 120° C. Areas of application: anti-ballistics,
sports articles and automotive industry.
PA12: TEPEX® x06, very good surface properties and UV resistance.
Easily formed at approx. 210°C. Mechanical properties not quite
on a par with PA6.6. Melting temperature is 180° C, forming temperature
200-220° C and continuous use temperature 90° C. Areas of
application: electronics, automotive industry (interior uses).
TPU
TEPEX® x08, with TPU as the matrix material, is of particular
interest to the footwear industry. The material is highly shock-resistant
and easy to bond, paint and overmould, even at low temperatures. Melting
temperature is 190° C, forming temperature 200-220° C and
continuous use temperature 90° C. Areas of application include
sports articles and industrial products.
PPS
TEPEX® x07 exhibits exceptional chemical resistance, very high
temperature resistance and good mechanical properties. By virtue of
its refractoriness, PPS may be used inside aircraft. Melting temperature
is 280° C, forming temperature approx. 310° C and continuous
use temperature 220° C. Applications: principally in aviation
and industrial products.
Woven fabric types Woven fabrics
Woven fabrics are generally used in high-performance composites to
reinforce them. A wide range of different types of woven fabrics are
used, the most familiar being linen weave, twill weave and satin weave.
The density of the fibre and the type of weave critically influence
the forming properties and the characteristics of the finished product.
