Composites

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 materials 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.

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

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 and superior surface properties than 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 and automotive industry.

TPU
TEPEX^® x08, with TPU as 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 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 plain 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.