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Chemical and Heat Resistance of AMODEL® Polyphthalamide Helps Low-coolant Sensor Survive Harsh Operating Environment

Innovative design from Entratech Systems resists corrosion in new long-life coolants

A new low-coolant sensor from Entratech Systems of Sandusky, Ohio is designed to be located in the radiators of trucks, off-road vehicles, and marine equipment. The housing of the sensor is molded of AMODEL® AS-1933 HS polyphthalamide (PPA) resin from Solvay Advanced Polymers, L.L.C.

"Typically these sensors are put into a cooling system's expansion tank," explains Mike Richardson, president of Entratech Systems, "but because of the high-temperature properties of the AMODEL resin, this new design can be installed directly into the radiator."

Unique design, unique material

Conventional sensors send a continuous current path through a metal probe tip immersed in the coolant. The hybrid organic-acid technology (HOAT) used in new long-life engine coolants, however, can corrode the probe through the action of electrolysis.

Richardson's design uses a proprietary AC type of signal sent through a stainless steel probe. The sensor incorporates special circuitry with an on-board microchip to process the signal from the coolant. A connecting wire to an indicator lamp or other warning device alerts the equipment operator to a low-coolant situation. The circuit can be interfaced to engine computers, it performs a power-up self test, and it features a time delay to prevent false alarms caused by sloshing of coolant in normal operation.

The unit's stainless steel probe is insert molded into a housing that features integral threads for mounting the sensor into the coolant through a threaded hole in a radiator or expansion tank. A composite design was needed to insulate the probe from a metal tank. Richardson specified the AMODEL material because it is able to retain its dimensional stability at the elevated temperatures encountered in a vehicle cooling system, preventing leaks at the sensor's installation site.

Operating performance and processing ease

AMODEL® AS-1933 HS grade of polyphthalamide was developed specifically for improved performance in automotive cooling system environments. This material exceeds industry performance requirements even when tested at temperatures as high as 135°C (275°F). It also resists degradation or dimensional change after prolonged exposure to conventional glycol or long-life HOAT coolants. This glass-reinforced grade can be readily processed using conventional equipment and methods.

Entratech molds its housing on a press that has cartridge heaters in each mold half. Richardson says, "the material runs well, and we have not experienced any instances of incomplete mold fill." Maximum part density was established through experimentation and programmed into the molding machine computer. In final assembly, the probe is attached to the circuit board by a threaded stud, and the board is encapsulated in a two-part epoxy potting resin. Power, ground, and signal wires exit the potting for appropriate attachment to a vehicle's electrical system.

About Solvay Advanced Polymers

Solvay Advanced Polymers, L.L.C. is a subsidiary of Solvay America, Inc., the U.S. holding company of Solvay S.A. The company produces high-performance polymers that are used in a wide range of demanding applications in the automotive, aerospace, industrial, foodservice, medical and electronics industries worldwide. Solvay Advanced Polymers products include the IXEF® polyarylamide and PRIMEF® polyphenylene sulfide product lines of Solvay S.A. combined with a portfolio of materials (more) Add 2 – New AMODEL® PPA selected for housing of engine coolant heater that had comprised BP Amoco's engineering resins business. More information about this and other Solvay Advanced Polymers products and services can be found on the company's website at www.solvayadvancedpolymers.com.

Solvay S.A. is an international pharmaceuticals and chemicals group with headquarters in Brussels, Belgium, employing about 30,000 people in 50 countries. In 2002, its consolidated sales amounted to EUR 7.9 billion generated by its four activity sectors: Pharmaceuticals, Chemicals, Plastics and Plastics Processing. Solvay S.A. is listed in the Euronext 100 index of top European companies. Details are available at www.solvay.com.

About Entratech Systems

For twenty years, Entratech Systems has been supplying the automobile, trucking, marine, and power-generation industries with electronic sensors for fuel and coolant systems. At its facility in Sandusky, Ohio, the company manufactures a short list of standard designs along with a variety of custom assemblies. Here its goal of producing high-quality, affordable products is being met. Its catalog of useful and innovative household designs includes High Water Alarms™, Hingemate™ security hinges, Stud-Pro™ construction drilling devices, and Infoplate Plus™ wall mounts for computer connections. For more information, see the company website at www.entratechsystems.com