Hexamethylenediamine curative in guanidine-free cure systems for AEM

摘要

The vulcanization system most frequently used in ethylene acrylic elastomers (AEM) compounds is a combination of HMDC (hexamethylenediamine carbamate) with DOTG (di-o-tolylguanidine) or DPG (diphenylguanidine). HMDC breaks down into HMDA (hexamethylenediamine) and carbon dioxide (CO2) when it is exposed to heat and/or moisture. During the high temperatures seen in the cure process, the HMDC is converted to HMDA, which is the active curing agent for the AEM (see figure 1a). The active curing agent (HMDA) for the AEM is the same whether starting with HMDC or HMDA; the only difference is that HMDC liberates both the HMDA and CO2. The HMDC curative is the second highest cost component of AEM compounds. The mechanism (ref. 1) for curing AEM with hexamethylenediamine is shown in figure 1b.