Testing and Evaluation of Injection Molded Magnets in Engine and Ignition Environments

An experimental investigation was conducted with injection molded magnets for use with Hall sensors in automotive applications. Two groups of nylon 6 based and one group of nylon 12 based magnets, each containing approximately 88 percent strontium-ferrite, were exposed to a variety of environmental conditions (long term exposure to air, oil, transmission fluid at elevated temperature). The tensile strength and elongation of the magnets were monitored and recorded. It was found that there was a significant difference in the performance of the two nylon 6 based groups. The nylon 12 based group exhibited a performance consistent with the expectations. In designing with injection molded magnets, one must take into consideration the changes in properties as a function of environmental effects.