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Ben Moffat, project engineer at Variohm, was looking for a potting compound that would give them the best thermal conductivity combined with an extended pot life at room temperature - and it needed to be as free flowing as possible to fill the very small cavities in the Variohm M4 to M10 sized thermistor and thermocouple probes. These can typically work at over 100C and can be called on to work at temperatures of 200 to 300C - so very high temperature capability was needed as well.
Intertronics Sales Manager Kevin Cook suggested Polytec TC 437, a boron nitride filled thermally conductive epoxy which cures at room temperature with a two hour pot life and low viscosity. “With Polytec we have about three times the pot life we had before and the bubbles rise to the top so we can pretty much do what we want with it. Intertronics provided a selection of dispensing tips and were helpful in guiding us through the trials process, so that now it is quite quick and clean," says Moffat. "Polytec TC 437 is now our preferred material, especially for the high performance and difficult assemblies. The market need is for high temperature thermistors and with the setup from Intertronics we can feel secure at elevated working temperatures.”
In addition Intertronics were able to supply bulk quantities of the Polytec TC 437 adhesive in a Variohm green to match their corporate style.
The process is manual at present, so providing a material with user-friendly pot life and viscosity reduced mess and clean up. “Manual epoxy potting is as versatile as we need, but in future we intend to develop the system by use of a time based dispenser run from compressed air and operated by a foot switch.”
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