Polycarbonate for Automotive Applications

Makrolon^® is an amorphous, thermoplastic molding compound. It is noted for its high light transmission, high heat resistance, high toughness, high creep modulus, high dimensional stability and good electrical insulation properties. Glass fiber reinforced Makrolon^® has a particularly high rigidity, coupled with very good dimensional stability. The production plants for Makrolon^® have been certificated to DIN ISO by the competent certification companies.

Product Characteristics

• Inherent color - Clear and transparent, like glass
• Toughness - Without notching, no failure; high notched impact strength
• Dimensional accuracy and stability - Exceptionally high, since no change in dimensions due to water absorption and post shrinkage, high creep modulus, high heat deflection temperature, isotropic behavior
• Heat resistance - Glass transition temperature up to 148 °C
• Resistance to ignition sources - Fire classification up to UL 94V-0/1.5 mm and UL 94-5VA/3.0 mm; maximum temperature in glow wire test up to 960 °C
• Electrical insulation - Volume resistivity 1014 Ohm x m; dielectric strength up to 36 kV/mm (1 mm wall thickness)
• Miscellaneous - Makrolon^® grades for food contact and medical engineering applications

Makrolon and the Automotive Industry

The automotive industry requires materials that permit lightweight construction and are absolutely reliable in continuous service. Materials should also offer a high potential for integrating different functions in order to permit all-in components or systems to be produced. Freedom of design is also of major importance.

Other forms of transport (e.g. trucks, air traffic, etc.) see Makrolon^®.

Properties and Reasons for Using Makrolon^® in Automotive Engineering

• High toughness even at low temperatures - The toughness (unnotched) of Makrolon^® at -30 °C is comparable to that at room temperature.
• Transparency/Coloring - Makrolon^® is crystal clear, allowing it to be colored easily in any desired shade. Standard colors are available for virtually all traffic signal types (e.g. indicator lenses and car tail lights).
• Weather resistance - The colors used for light signals must not undergo any change even when used outdoors. UV-stabilized Makrolon^® grades have demonstrated excellent mechanical strength and colorfastness over a period of many years. The surface can be additionally stabilized by coating it with a suitable light stabilizer system for particularly critical applications.
• High dimensional stability in heat - Non-reinforced Makrolon^® has a Vicat-B softening temperature of 145-150 °C. This outstanding property makes Makrolon® suitable for automotive headlamps.

Special Requirements for Automotive Lighting

The Makrolon^® AL grades (AL stands for Automotive Lenses) have been specially developed for the production of plastic headlamp diffusers which are required to comply with stringent, internationally prescribed requirements, ATI KU28012 Makrolon^® AL2447 and AL2647

The AL grades differ from general-purpose grades through their improved optical properties, greater purity, better temperature stability and minimum color tolerances.

Stringent requirements on scratch resistance, weatherability and chemical resistance call for an additional surface finish in the form of a hard coating.

Makrolon^® AL has major advantages over the conventional material used for headlamp diffusers:

• Significant weight reduction
• Freedom of design
• Improved optical function through more precise prisms with a higher reproduction accuracy
• Possibility of component integration.

The dimensional stability in heat of Makrolon^® AL may not suffice on small-volume headlamps or where there is a too small a gap between the headlamp diffuser and the light source. It is possible to use Apec^® with a Vicat softening temperature of up to 205°C by way of a high-grade alternative here.