FortronŽ PPS Provides Thermal Stability and Impact Resistance in Auto Parking Brake Actuator and Gears
September 15, 2005
FLORENCE, Ky.; KELSTERBACH -- Automotive electronic parking brake systems call for tough materials that meet challenging conditions. This is especially true of the actuators at the rear wheels, where carmakers like Audi, Volkswagen, Bentley, Bugatti and Lancia have begun using FortronŽ linear polyphenylene sulfide (PPS) for actuator housings and the gears that help transfer power from the actuator motor to the brakes.
Fortron PPS, which is produced by Ticona, the engineering polymers business of the Celanese Corporation, was selected for these parts because of its dimensional stability across a wide temperature range, impact resistance, chemical resistance and processability.
Electromechanical parking brakes are operated by a switch in the passenger compartment that activates actuators at the rear brake calipers via electric wires. These brakes prevent a car from rolling on inclines as steep as 30 percent and remain active until the car has enough forward speed not to roll back.
Each PPS actuator housing is made up of an injection molded body and cover. While the size of the housing varies somewhat with the vehicle, it generally measures about 130 mm long, 50 mm wide and 80 mm high. The two components are ultrasonically welded to create the final assembly. The PPS spur gear within the actuator has a diameter of about 30 mm and is driven by a belt from an electric motor. The gear then drives a transmission that actuates the brake.
The key requirement that led to the selection of Fortron PPS in the actuator is its ability to remain dimensionally stable at temperatures from well below 0°C to 180°C. It was also chosen because it withstands the impact of stones thrown up by tires from the road surface and it has excellent resistance to brake fluid and other automotive chemicals. Fortron PPS also flows well in molding to create low-flash parts, which eliminates the need for costly secondary finishing steps, especially for the gears. Fortron PPS is a high-performance plastic having inherent flame retardancy, high hardness and rigidity, and continuous service temperatures to 240°C. It also has excellent chemical and oxidation resistance, minimal water absorption and low creep, even at elevated temperatures. It is used widely in many industries, especially in the automotive, aerospace and electrical/electronics sectors.
About Ticona and Celanese
Ticona Technical Polymers is one of the businesses of Celanese Corporation. Ticona produces and markets a broad range of engineering polymers and achieved sales of $863 million in 2004. Ticona has approximately 2,000 employees at production, compounding and research facilities in the USA, Germany and Brazil.
Celanese Corporation (NYSE:CE) is an integrated global producer of value-added industrial chemicals with 2004 sales of $ 5 billion. Based in Dallas, Texas, the company holds #1 or #2 market positions in products comprising the majority of its sales and has four major businesses: Chemicals Products, Technical Polymers Ticona, Acetate Products and Performance Products. Celanese has 29 production plants, with major operations in North America, Europe and Asia.
