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MATERIAL PROVIDES CHEMICAL RESISTANCE, MANUFACTURING ECONOMY IN CONVERSION FROM ALUMINUM
The housing is mounted on the cylinder head, and it positions the thermostat in the stream of hot coolant as it exits the engine. In the engine’s original front-wheel-drive configuration, its thermostat housing was machined from aluminum in one piece with the air-intake manifold. When the engine was adapted for a reardrive configuration, the decision was made to give the new design a plastic intake manifold and to make the thermostat housing a separate part. AMODEL AS-1933 HS was selected for the new housing. “We chose the AMODEL material because of its properties,” said Dipan Patel, senior engineer for the rear-wheel-drive engine group. He points out that the engine uses HOAT-technology, long-life coolant, which has different additives than regular glycol-based coolants and can wear away other plastics. However, glass-filled AS-1933 HS features proprietary technology for improved chemical resistance. “This AMODEL grade is more resistant to the coolant than nylon 6/6,” says Patel. AMODEL AS-1933 HS was also chosen for its temperature performance. Patel notes that the housing needs to maintain its strength and ductility from –20°F to 240°F, with a normal maximum operating temperature of 225°F. With a heat-deflection temperature of 530°F, this range is easily within the material’s performance envelope. Manufacturing considerations Where a cast aluminum part would need to be machined to its final configuration, the new thermostat housing is injection molded as a net shape. Brass inserts for attachment bolts are pressed into the housing’s flange, and threaded steel inserts are molded into the part for attaching a stamped steel water outlet. The superior mechanical properties of AMODEL AS-1933 HS at elevated temperatures result in excellent torque retention once the housing is bolted to the cylinder head. The part is molded by Miniature Precision Components (MPC, Inc.) at its facility in Walworth, Wisconsin. “Solvay provided technical support and worked with MPC to optimize the molding process,” says Patel, “helping to establish a stable processing window that consistently results in good quality parts.” AMODEL resin crystallizes rapidly, leading to faster molding cycles in thick or thin sections. This can lead to lower total-piece costs, which is a significant advantage over materials that may require longer molding cycles. http://www.solvayadvancedpolymers.com
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