Formulation Suggestions for Replacing DOTG in AEM Compounds

AEM (DuPont Vamac® ethylene acrylic elastomer) compounds are used to make high performance parts like turbocharger hoses and automotive gaskets.  The compounds are usually cured with diamines and for many years the accelerator of choice was has been diorthorotolyl guanidine (DOTG). The use of DOTG may be limited in the future. 

Alternative accelerators have been identified that can be used to replace DOTG in AEM compounds and these alternative accelerators are being used successfully in commercial AEM compounds.  Often the only formulation change required is to directly replace the DOTG with an alternative accelerator and then the compound will meet the end use requirements.  Some formulations may require additional minor adjustments beyond just replacing the accelerator. 

This paper will review studies that we have undertaken to evaluate a replacement for DOTG and still meet the key end use requirements.  One of the modifications we identified was to change the level of black and/or the type of black so as to lower the hardness and/or modulus to match with the original compound.  This change also increased the elongation so that it was closer to the original.  When necessary, the compression set values for the compounds using the new accelerators was improved using several different approaches.  One approach was to use a less volatile plasticizer and another way was to use blends of the “standard” AEM polymers and the recently developed higher viscosity AEM polymers.  The combination of the formulation changes allowed for replacement of the DOTG in AEM compounds without sacrificing performance.

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